Abstract:
A drug delivery medical device such as a gastrointestinal stent comprises a support  1  which has an outer cover or coating  2 . The cover or coating comprises a plurality of patches or tiles  3  of a polymeric material which contain a drug. The patches  3  form a continuous or discontinuous mosaic. The patches may be held together using a biodegradable adhesive.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 61/287,845, filed Dec. 18, 2009, the entire contents of which are incorporated herein by reference. 
     
    
     INTRODUCTION 
       [0002]    The invention relates to drug delivery systems. The invention also relates to drug eluting medical devices such as stents. 
         [0003]    Drug delivery coatings for medical devices, such as stents, can take a number of forms. In one case, a device is coated with a drug delivery coating comprising a monolthic polymer within which is dissolved the drug to be eluted. The drug is released either by dissolution of the polymer or by diffusion from the polymer. Coatings that release drug through dissolution are made from polymers that have established adsorption, distribution, metabolism and excretion (ADME) profiles. This restricts the selection of coating polymers and also makes the development of such polymers very expensive and time consuming. Coatings that do not dissolve can lead to much of the drug remaining un-eluted or “sequestered” within the polymer. For devices that are intended to be permanent implants this can lead to questions regarding long term safety. 
         [0004]    Polyurethane and polyurea polymers are well known in the art and have been in use for decades. With a wide variety of potential chemical structures and properties these polymers have found applications in many diverse fields. In recent years polyurethanes have been extensively used in biomedical applications due to their accepted biocompatibility. 
         [0005]    The structure of a polyurethane polymer can be generally described as a copolymer with a soft segment and a hard segment. The hard segment generally has stiffer bonds than the soft segment, which is reflected in a higher glass transition temperature (Tg). The stiffness of the hard segment can be attributed to the presence of a urethane/urea group or oligomer. The molecular weight ratio of hard segment to soft segment has a critical impact on the mechanical properties of the final polymer as does the chemical nature of either segment. 
         [0006]    Historically, in the preparation of polyurethane polymers, chemists have used polyethers as soft segments due to the mobiliy of their chains. Typical polyether polymers are polyethylene oxide (PEO), polypropylene oxide (PPO) or the higher homologues. 
         [0007]    PEO and to a much lesser extent PPO can facilitate additional hydrogen bonding between segments thus yielding improved mechanical characteristics. Reduction in the ability of the soft segment to hydrogen bond with the hard segment has generally lead to poor tensile strengths. 
         [0008]    Polyethers also impart significant hydrophilicity to poyurethanes but the effect decreases with higher polyether homologues. The propensity for these materials to undergo hydrolytic, oxidative and enzymatic degradation increases with hydrophilicity. 
         [0009]    In more recent years alternative polymers have been used as soft segments to improve the biostability of polyurethanes but the mechanical properties of these have been limited. 
         [0010]    The hard segment of a polyurethane polymer is the region rich in urethane or urea linkages formed from the reaction of diisocyanate molecules. These may be a single urethane or urea linkage or may be multiple repeat units covalently bound via urethane or urea bonds. 
         [0011]    Diisocyanates can be divided into aromatic type and aliphatic type. The aromatic type is the preferred molecule. Aromatic diisocyanates yield bonds that have restricted rotation and thus low mobility due to their bulky nature. Such aromatic systems provide stiff chains to function as hard segments, which mechanically reinforce a polymer improving greatly the tensile properties of the polymer. 
         [0012]    Aliphatic diisocyanates on the other hand typically form bonds of greater mobility thus resulting in hard segments which do not contribute greatly to the mechanical properties on the final polymer. 
         [0013]    In recent years biostable polyurethanes have received a lot of attention and there are now several commercial products of this type that are designed for implantation in the body. These products tend to be solid elastomers of varying hardness. 
         [0014]    In order to achieve improvements in biostability varying proportions of the conventional and chemically labile polyether soft segments have been substituted with more robust molecules. Examples of improved soft segment molecules include polyolefins, polycarbonates and polysiloxanes. 
         [0015]    However, incorporation of such alternative soft segments into polyurethane formulations, reduces the ability of the soft segment to form hydrogen and other intermolecular bonds with neighbouring chains. This limits the elongation and tensile properties of the final material. In addition, because many of the new biostable soft segments are hydrophobic they induce incompatibility with aqueous reagents. Because foam formation in polyurethane chemistry involves reaction with water (water blowing) such reactions are not reliable currently with hydrophobic soft segments. 
         [0016]    In summary, there is an emerging trend towards more biostable commercial polyurethane materials utilising unconventional soft segments. However, all of the emerging materials are elastomers and no foams are available. In addition, because many of the newer soft segment materials do not hydrogen bond well they lack mechanical characteristics which are desirable for some applications. 
       SUMMARY OF THE INVENTION 
       [0017]    According to the invention there is provided a drug eluting medical device comprising a support and a plurality of individual tiles for at least portion of the support, at least one of the tiles comprising a polymeric material containing a drug. 
         [0018]    In one embodiment the device comprises retaining means for at least temporarily retaining at least some of the tiles. The retaining means may comprise connecting means between at least some of the tiles. 
         [0019]    The connecting means may be at least partially biodegradable. 
         [0020]    In one case connecting means comprises an adhesive such as a cyanoacrylate. 
         [0021]    In another embodiment the connecting means comprises a mesh. The mesh may comprise a fibrous mesh. 
         [0022]    In one embodiment at least some of the fibres of the mesh are at least partially biodegradable. 
         [0023]    In one case the tiles form a substantially continuous mosaic on the support. 
         [0024]    In another case the tiles form a substantially discontinuous mosaic on the support. 
         [0025]    In a further embodiment the retaining means comprises a first support and a second support, at least some of the tiles being located between the first and second supports. 
         [0026]    In one case at least one of the first and second supports are biodegradable. Only one of the first and second supports may be biodegradable. Alternatively the first and second supports are biodegradable. 
         [0027]    In one embodiment the support comprises a scaffold. 
         [0028]    The support may comprise a stent. 
         [0029]    In one embodiment the device comprises a valve. The valve may be mounted to the support. 
         [0030]    In one case the device comprises a drug eluting gastrointestinal stent. 
         [0031]    According to the invention there is provided a drug delivery system comprising a biomaterial containing a therapeutic agent, the biomaterial having properties that are matched to the tissue to which the drug delivery system is to be applied. In one embodiment the properties comprise viscoelastic and/or mechanical properties. 
         [0032]    In one embodiment the tissue comprises a portion of the alimentary canal. 
         [0033]    In one case the biomaterial has different domains and the therapeutic agent is located in only some of the domains. 
         [0034]    In one embodiment the biomaterial comprises a foam. 
         [0035]    According to certain embodiments of the invention the biomaterial is a triblock copolymer of formula I: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein the copolymers are chemically interspersed (bound) between urethane and/or urea linkages and wherein each of X, Y, m, n, p, L 1 , L 2 , R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  is as defined and described herein. 
         [0036]    In certain embodiments, the drug delivery system comprises a polyurethane/urea foam comprising a triblock copolymer of formula I as defined and described herein. 
         [0037]    In some embodiments, the present invention provides a pre-formed soft segment for a polyurethane/urea foam wherein the soft segment is of formula I as defined and described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0038]      FIG. 1  is an illustration of prior art polymers with urea and urethane linkages interspersed between homopolymer soft segments; 
           [0039]      FIG. 2  is an illustration of a polyurethane/urea foam according to the invention with urea and urethane linkages interspersed between triblock copolymer soft segments; 
           [0040]      FIG. 3  is an illustration of a siloxane and polypropylene oxide based triblock copolymer in different forms; 
           [0041]      FIG. 4  is a graph of comparative mechanical properties of homo (VF130309) and triblock copolymer (VF230209A) soft segments; 
           [0042]      FIG. 5  is a graph of comparative mechanical properties of homo (VF190309) and triblock copolymer (VF090309) soft segments; 
           [0043]      FIG. 6  is a graph illustrating the mechanical performance of triblock copolymer soft segments versus homopolymer soft segment during accelerated aging in simulated gastric fluid; 
           [0044]      FIG. 7  depicts a gastric yield pressure test apparatus as utilized in Example 10; 
           [0045]      FIG. 8A  and  FIG. 8B  depict results of accelerated stability of a valve prepared from a viscoelastic foam of the present invention; 
           [0046]      FIG. 9  is an illustration of microphase separation in segmented copolymer (a) Schematic and (b) AFM image; 
           [0047]      FIG. 10  illustrates segment re-orientation during mechanical stress; 
           [0048]      FIG. 11  is an image of the cellular structure of the foam; 
           [0049]      FIG. 12  is a schematic representation of drug molecules in foams with struts of different dimensions; 
           [0050]      FIG. 13  is a graph illustrating the compression and hystesis behaviour of the foam material; 
           [0051]      FIG. 14  is a graph of mass uptake of ethanol by three different formulations of biomaterial; 
           [0052]      FIG. 15  is a graph of release profiles of metronidazole from a film biomaterial; 
           [0053]      FIG. 16  is a graph of release profiles of metronidazole from film biomaterial; 
           [0054]      FIG. 17  is a graph of release profiles of cyclosporine from biomaterials; 
           [0055]      FIG. 18  is an isometric view of a medical device according to the invention; 
           [0056]      FIG. 19  is an exploded view of part of the device of  FIG. 18 ; 
           [0057]      FIG. 20  is an isometric, partially exploded and cut-away view of another mechanical device; 
           [0058]      FIG. 21  is an isometric, partially cut-away view of a further medical device according to the invention; 
           [0059]      FIG. 22  is an exploded view of the device of  FIG. 21 ; 
           [0060]      FIG. 23  is an isometric partially cut-away view of another medical device according to the invention; 
           [0061]      FIG. 24  is a cross sectional view of a tile part of the device of  FIG. 23 ; 
           [0062]      FIG. 25  is a plan view of the tile part; 
           [0063]      FIG. 26  is an isometric partially cut-away view of a further medical device according to the invention; 
           [0064]      FIG. 27  is an enlarged view of a detail of the device of  FIG. 26 ; 
           [0065]      FIG. 28  is an isometric partially cut-away view of a still further medical device according to the invention; and 
           [0066]      FIG. 29  is a plan view of one tile of the device of  FIG. 28 . 
       
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
       [0067]    Referring to the drawings and initially to  FIGS. 18 and 19  thereof there is illustrated a medical device which in this case comprises a drug eluting gastrointestinal stent. The stent comprises a support  1  which has an outer cover  2 . The cover or coating  2  comprises a plurality of patches or tiles  3  of drug containing polymer. The patches  3 , which may be held together in a number of ways, form a mosaic that covers the desired portion of the device. The mosaic may be continuous or discontinuous. The patches  3  may be held together with biodegradable adhesive, such as a cyaoacrylate adhesive. 
         [0068]    In one case device is an anti-reflux device for the upper digestive tract as shown in  FIG. 20 . The device comprises a support scaffold  5  on which the tiles  3  are mounted. An anti-reflux valve  10  is also mounted to the support  5 . The valve may be of the type described in our US2010-0137998A, the entire contents of which are incorporated herein by reference. 
         [0069]    Alternatively as illustrated in the embodiment of  FIGS. 21 and 22  the patches  3  may be sandwiched between two scaffolds  11 ,  12 . Both of the scaffolds may be degradable. Alternatively one of the scaffolds is degradable and the other is a non-degradable scaffold. 
         [0070]    Referring to  FIGS. 23 to 25  there is illustrated another device according to the invention which is similar to the device of  FIG. 20  and like parts are assigned the same reference numerals. In this case the tiles  3  are bonded to the support for example by using a suitable biodegradable adhesive. 
         [0071]    Referring to  FIGS. 26 and 27  there is illustrated another medical device which is again similar to the device of  FIG. 20  and like parts are assigned the same reference numerals. In this case the tiles  3  are interconnected by a mesh  20  which may be of fibre. The mesh  20  may be of an at least partially biodegradable material. 
         [0072]    Referring to  FIGS. 28 and 29  there is illustrated a still further device according to the invention which is similar to the device of  FIG. 20  and like parts are assigned the same reference numerals. In this case there is a mechanical interengagement between the tiles  3  in the mosaic. The tiles  3  may have tongues  30  and/or grooves  31  for interengagement with corresponding tongues and/or groves of adjacent tiles. 
         [0073]    The means for holding the mosaic intact may degrade at a rate slower than the rate of drug release thus facilitating drug elution before loss of mechanical integrity. Alternatively the mosaic may degrade at a rate much slower than the rate of drug release ensuring total drug release prior to loss of mechanical integrity. When the mosaic looses mechanical integrity the patches or tiles will no longer be held at the target site and in the case of a body lumen will pass through with bodily fluids. 
         [0074]    This type of system is particularly suitable for use in the digestive system where the non-degrading polymer will ultimately be excluded from the body. 
       General Description: 
       [0075]    Use of polyethers as soft segments in polyurethane foams is know to result in soft elastic and viscoelastic materials due to the dynamic reinforcing effect of hydrogen bonding. Conversely, use of non-hydrogen bonding hydrophobic soft segments results in harder, less elastic material. Blending of such hydrophobic and hydrophilic homopolymer soft segments as shown in  FIG. 1  via urethane/urea linkages is known in the art to achieve mechanical properties appropriate to specific applications. 
         [0076]    Acid catalysed hydrolytic degradation occurs at urethane linkages within polyurethane materials. These urethane/urea linkages are therefore the ‘weak-links’ of the polyurethane material. It follows that the intrinsic hydrophilicity of the polyurethane material will affect the rate of hydrolysis through modulation of water uptake. Thus, such materials are incompatible with use in a gastric environment (i.e., a highly acidic aqueous environment). 
         [0077]    Thus, in some embodiments, the present invention provides a multiblock copolymer that is biomimetic and hydrolytically stable in a gastric environment. Such multiblock copolymers are of formula I: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein: each           represents a point of attachment to a urethane or urea linkage;
 
each of X and Y is independently a polymer or co-polymer chain formed from one or more of a polyether, a polyester, a polycarbonate, or a fluoropolymer;
 
each of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently selected from one or more of R, OR, —CO 2 R, a fluorinated hydrocarbon, a polyether, a polyester or a fluoropolymer;
 
each R is independently hydrogen, an optionally substituted C 1-20  aliphatic group, or an optionally substituted group selected from phenyl, 8-10 membered bicyclic aryl, a 4-8 membered monocyclic saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulphur, or 5-6 membered monocyclic or 8-10 membered bicyclic heteroaryl group having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
 
each of m n and p is independently 2 to 100; and
 
each of L 1  and L 2  is independently a bivalent C 1-20  hydrocarbon chain wherein 1-4 methylene units of the hydrocarbon chain are optionally and independently replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)N(R)—, —N(R)C(O)—, —SO 2 —, —SO 2 N(R)—, —N(R)SO 2 —, —OC(O)—, —C(O)O—, or a bivalent cycloalkylene, arylene, heterocyclene, or heteroarylene, provided that neither of L 1  nor L 2  comprises a urea or urethane moiety.
 
       DEFINITIONS 
       [0078]    Compounds of this invention include those described generally above, and are further illustrated by the classes, subclasses, and species disclosed herein. As used herein, the following definitions shall apply unless otherwise indicated. For purposes of this invention, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75 th  Ed. Additionally, general principles of organic chemistry are described in “Organic Chemistry”, Thomas Sorrell, University Science Books, Sausalito: 1999, and “March&#39;s Advanced Organic Chemistry”, 5 th  Ed., Ed.: Smith, M. B. and March, J., John Wiley &amp; Sons, New York: 2001, the entire contents of which are hereby incorporated by reference. 
         [0079]    As described herein, compounds of the invention may optionally be substituted with one or more substituents, such as are illustrated generally above, or as exemplified by particular classes, subclasses, and species of the invention. It will be appreciated that the phrase “optionally substituted” is used interchangeably with the phrase “substituted or unsubstituted.” In general, the term “substituted”, whether preceded by the term “optionally” or not, refers to the replacement of hydrogen radicals in a given structure with the radical of a specified substituent. Unless otherwise indicated, an optionally substituted group may have a substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this invention are preferably those that result in the formation of stable or chemically feasible compounds. The term “stable”, as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and preferably their recovery, purification, and use for one or more of the purposes disclosed herein. In some embodiments, a stable compound or chemically feasible compound is one that is not substantially altered when kept at a temperature of 40° C. or less, in the absence of moisture or other chemically reactive conditions, for at least a week. 
         [0080]    The term “aliphatic” or “aliphatic group”, as used herein, denotes a hydrocarbon moiety that may be straight-chain (i.e., unbranched), branched, or cyclic (including fused, bridging, and spirofused polycyclic) and may be completely saturated or may contain one or more units of unsaturation, but which is not aromatic. Unless otherwise specified, aliphatic groups contain 1-20 carbon atoms. In some embodiments, aliphatic groups contain 1-10 carbon atoms. In other embodiments, aliphatic groups contain 1-8 carbon atoms. In still other embodiments, aliphatic groups contain 1-6 carbon atoms, and in yet other embodiments aliphatic groups contain 1-4 carbon atoms. Suitable aliphatic groups include, but are not limited to, linear or branched, alkyl, alkenyl, and alkynyl groups, and hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or (cycloalkyl)alkenyl. 
         [0081]    The term “lower alkyl” refers to a C 1-4  straight or branched alkyl group. Exemplary lower alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl. 
         [0082]    The term “lower haloalkyl” refers to a C 1-4  straight or branched alkyl group that is substituted with one or more halogen atoms. 
         [0083]    The term “heteroatom” means one or more of oxygen, sulfur, nitrogen, phosphorus, or silicon (including, any oxidized form of nitrogen, sulfur, phosphorus, or silicon; the quaternized form of any basic nitrogen or; a substitutable nitrogen of a heterocyclic ring, for example N (as in 3,4-dihydro-2H-pyrrolyl), NH (as in pyrrolidinyl) or NR +  (as in N-substituted pyrrolidinyl)). 
         [0084]    The term “unsaturated”, as used herein, means that a moiety has one or more units of unsaturation. 
         [0085]    As used herein, the term “bivalent C 1-8  [or C 1-6 ] saturated or unsaturated, straight or branched, hydrocarbon chain”, refers to bivalent alkylene, alkenylene, and alkynylene chains that are straight or branched as defined herein. 
         [0086]    The term “alkylene” refers to a bivalent alkyl group. An “alkylene chain” is a polymethylene group, i.e., —(CH 2 ) n —, wherein n is a positive integer, preferably from 1 to 6, from 1 to 4, from 1 to 3, from 1 to 2, or from 2 to 3. A substituted alkylene chain is a polymethylene group in which one or more methylene hydrogen atoms are replaced with a substituent. Suitable substituents include those described below for a substituted aliphatic group. 
         [0087]    The term “alkenylene” refers to a bivalent alkenyl group. A substituted alkenylene chain is a polymethylene group containing at least one double bond in which one or more hydrogen atoms are replaced with a substituent. Suitable substituents include those described below for a substituted aliphatic group. 
         [0088]    The term “halogen” means F, Cl, Br, or I. 
         [0089]    The term “aryl” used alone or as part of a larger moiety as in “aralkyl”, “aralkoxy”, or “aryloxyalkyl”, refers to monocyclic or bicyclic ring systems having a total of five to fourteen ring members, wherein at least one ring in the system is aromatic and wherein each ring in the system contains 3 to 7 ring members. The term “aryl” may be used interchangeably with the term “aryl ring”. 
         [0090]    As described herein, compounds of the invention may contain “optionally substituted” moieties. In general, the term “substituted”, whether preceded by the term “optionally” or not, means that one or more hydrogens of the designated moiety are replaced with a suitable substituent. Unless otherwise indicated, an “optionally substituted” group may have a suitable substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this invention are preferably those that result in the formation of stable or chemically feasible compounds. The term “stable”, as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and, in certain embodiments, their recovery, purification, and use for one or more of the purposes disclosed herein. 
         [0091]    Suitable monovalent substituents on a substitutable carbon atom of an “optionally substituted” group are independently halogen; —(CH 2 ) 0-4 R ∘ ; —(CH 2 ) 0-4 OR ∘ ; —O—(CH 2 ) 0-4 C(O)OR ∘ ; —(CH 2 ) 0-4 CH(OR ∘ ) 2 ; —(CH 2 ) 0-4 SR ∘ ; —(CH 2 ) 0-4 Ph, which may be substituted with R ∘ ; —(CH 2 ) 0-4 O—(CH 2 ) 0-1 Ph which may be substituted with R ∘ ; —CH═CHPh, which may be substituted with R ∘ ; —NO 2 ; —CN; —N 3 ; —(CH 2 ) 0-4 N(R ∘ ) 2 ; —(CH 2 ) 0-4 N(R ∘ )C(O)R ∘ ; —N(R ∘ )C(S)R β ; —(CH 2 ) 0-4 N(R ∘ )C(O)NR ∘   2 ; —N(R ∘ )C(S)NR ∘   2 ; —(CH 2 ) 0-4 N(R ∘ )C(O)OR ∘ ; —N(R ∘ )N(R ∘ )C(O)R ∘ ; —N(R ∘ )N(R ∘ )C(O)NR ∘   2 ; —N(R ∘ )N(R ∘ )C(O)OR ∘ ; —(CH 2 ) 0-4 C(O)R ∘ ; —C(S)R ∘ ; —(CH 2 ) 0-4 C(O)OR ∘ ; —(CH 2 ) 0-4 C(O)SR ∘ ; —(CH 2 ) 0-4 C(O)OSiR ∘   3 ; —(CH 2 ) 0-4 OC(O)R ∘ ; —OC(O)(CH 2 ) 0-4 SR—, SC(S)SR ∘ ; —(CH 2 ) 0-4 SC(O)R ∘ ; —(CH 2 ) 0-4 C(O)NR ∘   2 ; —C(S)NR ∘   2 ; —C(S)SR ∘ ; —SC(S)SR ∘ , —(CH 2 ) 0-4 OC(O)NR ∘   2 ; —C(O)N(OR ∘ )R ∘ ; —C(O)C(O)R ∘ ; —C(O)CH 2 C(O)R ∘ ; —C(NOR ∘ )R ∘ ; —(CH 2 ) 0-4 SSR ∘ ; —(CH 2 ) 0-4 S(O) 2 R ∘ ; —(CH 2 ) 0-4 S(O) 2 OR ∘ ; —(CH 2 ) 0-4 OS(O) 2 R ∘ ; —S(O) 2 NR ∘   2 ; —(CH 2 ) 0-4 S(O)R ∘ ; —N(R ∘ )S(O) 2 NR ∘   2 ; —N(R ∘ )S(O) 2 R ∘ ; —N(OR ∘ )R ∘ ; —C(NH)NR ∘   2 ; —P(O) 2 R ∘ ; —P(O)R ∘   2 ; —OP(O)R ∘   2 ; —OP(O)(OR ∘ ) 2 ; SiR ∘   3 ; —(C 1-4  straight or branched alkylene)O—N(R ∘ ) 2 ; or —(C 1-4  straight or branched) alkylene)C(O)O—N(R ∘ ) 2 , wherein each R ∘  may be substituted as defined below and is independently hydrogen, C 1-6  aliphatic, —CH 2 Ph, —O(CH 2 ) 0-1 Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or, notwithstanding the definition above, two independent occurrences of R ∘ , taken together with their intervening atom(s), form a 3-12-membered saturated, partially unsaturated, or aryl mono- or bicyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, which may be substituted as defined below. 
         [0092]    Suitable monovalent substituents on R ∘  (or the ring formed by taking two independent occurrences of R ∘  together with their intervening atoms), are independently halogen, —(CH 2 ) 0-2 R • , -(haloR • ), —(CH 2 ) 0-2 OH, —(CH 2 ) 0-2 OR • , —(CH 2 ) 0-2 CH(OR • ) 2 ; —O(haloR • ), —CN, —N 3 , —(CH 2 ) 0-2 C(O)R • , —(CH 2 ) 0-2 C(O)OH, —(CH 2 ) 0-2 C(O)OR • , —(CH 2 ) 0-2 SR • , —(CH 2 ) 0-2 SH, —(CH 2 ) 0-2 NH 2 , —(CH 2 ) 0-2 NHR • , —(CH 2 ) 0-2 NR •   2 , —NO 2 , —SiR •   3 , —OSiR •   3 , —C(O)SR • , —(C 1-4  straight or branched alkylene)C(O)OR • , or —SSR •  wherein each R •  is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently selected from C 1-4  aliphatic, —CH 2 Ph, —O(CH 2 ) 0-1 Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. Suitable divalent substituents on a saturated carbon atom of R ∘  include ═O and ═S. 
         [0093]    Suitable divalent substituents on a saturated carbon atom of an “optionally substituted” group include the following: ═O, ═S, ═NNR* 2 , ═NNHC(O)R*, ═NNHC(O)OR*, ═NNHS(O) 2 R*, ═NR*, ═NOR*, —O(C(R* 2 )) 2-3 O—, or —S(C(R* 2 )) 2-3 S—, wherein each independent occurrence of R* is selected from hydrogen, C 1-6  aliphatic which may be substituted as defined below, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. Suitable divalent substituents that are bound to vicinal substitutable carbons of an “optionally substituted” group include: —O(CR* 2 ) 2-3 O—, wherein each independent occurrence of R* is selected from hydrogen, C 1-6  aliphatic which may be substituted as defined below, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. 
         [0094]    Suitable substituents on the aliphatic group of R* include halogen, —R • , -(haloR • ), —OH, —OR • , —O(haloR • ), —CN, —C(O)OH, —C(O)OR • , —NH 2 , —NHR • , —NR •   2 , or —NO 2 , wherein each R •  is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently C 1-4  aliphatic, —CH 2 Ph, —O(CH 2 ) 0-1 Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. 
         [0095]    Suitable substituents on a substitutable nitrogen of an “optionally substituted” group include —R † , —NR †   2 , —C(O)R † , —C(O)OR † , —C(O)C(O)R † , —C(O)CH 2 C(O)R † , —S(O) 2 R † , —S(O) 2 NR †   2 , —C(S)NR †   2 , —C(NH)NR †   2 , or —N(R † )S(O) 2 R † ; wherein each R †  is independently hydrogen, C 1-6  aliphatic which may be substituted as defined below, unsubstituted —OPh, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or, notwithstanding the definition above, two independent occurrences of R † , taken together with their intervening atom(s) form an unsubstituted 3-12-membered saturated, partially unsaturated, or aryl mono- or bicyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. 
         [0096]    Suitable substituents on the aliphatic group of R †  are independently halogen, —R • , -(haloR • ), —OH, —OR • , —O(haloR • ), —CN, —C(O)OH, —C(O)OR • , —NH 2 , —NHR • , —NR •   2 , or —NO 2 , wherein each R •  is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently C 1-4  aliphatic, —CH 2 Ph, —O(CH 2 ) 0-1 Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. 
       DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Multiblock Copolymers 
       [0097]    As described generally above, one embodiment of the present invention provides a triblock copolymer of formula I: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein the copolymers are chemically interspersed (bound) between urethane and/or urea linkages (i.e., at the bond designated with          ) and wherein each of X, Y, m, n, p, L 1 , L 2 , R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  is as defined and described herein. 
         [0098]    As defined generally above, the each of X and Y groups of formula I is independently a polymer or co-polymer chain formed from one or more of a polyether, a polyester, a polycarbonate, and a fluoropolymer. 
         [0099]    Examples of polymer or co-polymer chains represented by X and/or Y include: poly(ethylene oxide), poly(difluoromethyl ethylene oxide), poly(trifluoromethyl ethylene oxide), poly(propylene oxide), poly(difluoromethyl propylene oxide), poly(propylene oxide), poly(trifluoromethyl propylene oxide), poly(butylene oxide), poly(tetramethylene ether glycol), poly(tetrahydrofuran), poly(oxymethylene), poly(ether ketone), poly(etherether ketone) and copolymers thereof, poly(dimethylsiloxane), poly(diethylsiloxane) and higher alkyl siloxanes, poly(methyl phenyl siloxane), poly(diphenyl siloxane), poly(methyl di-fluoroethyl siloxane), poly(methyl tri-fluoroethyl siloxane), poly(phenyl di-fluoroethyl siloxane), poly(phenyl tri-fluoroethyl siloxane) and copolymers thereof, poly(ethylene terephthalate) (PET), poly(ethylene terephthalate ionomer) (PETI), poly(ethylene naphthalate) (PEN), poly(methylene naphthalate) (PTN), poly(butylene teraphalate) (PBT), poly(butylene naphthalate) (PBN), polycarbonate. 
         [0100]    In certain embodiments, the present invention provides a pre-formed soft segment for a polyurethane/urea foam. 
         [0101]    In some embodiments X is a polyether and Y is a polyether. More specifically in one case X and Y are both poly(propylene oxide). 
         [0102]    In certain embodiments, m and p are each independently between 2 and 50 and n is between 2 and 20. In some embodiments, m and p are each independently between 2 and 30 and n is between 2 and 20. 
         [0103]    As defined generally above, each of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently selected from one or more of R, OR, —CO 2 R, a fluorinated hydrocarbon, a polyether, a polyester or a fluoropolymer. In some embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is —CO 2 R. In some embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is —CO 2 R wherein each R is independently an optionally substituted C 1-6  aliphatic group. In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is —CO 2 R wherein each R is independently an unsubstituted C 1-6  alkyl group. Exemplary such groups include methanoic or ethanoic acid as well as methacrylic acid and other acrylic acids. 
         [0104]    In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently R. In some embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is an optionally substituted C 1-6  aliphatic group. In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is an optionally substituted C 1-6  alkyl. In other embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is an optionally substituted group selected from phenyl, 8-10 membered bicyclic aryl, a 4-8 membered monocyclic saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulphur, or 5-6 membered monocyclic or 8-10 membered bicyclic heteroaryl group having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulphur. Exemplary such R 1 , R 2 , R 3 , R 4 , R 5  and R 6  groups include methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, cyclobutyl, phenyl, pyridyl, morpholinyl, pyrrolidinyl, imidazolyl, and cyclohexyl. 
         [0105]    In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently —OR. In some embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is —OR wherein R is an optionally substituted C 1-6  aliphatic group. In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is —OR wherein R is C 1-6  alkyl. In other embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is —OR wherein R is an optionally substituted group selected from phenyl, 8-10 membered bicyclic aryl, a 4-8 membered monocyclic saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulphur, or 5-6 membered monocyclic or 8-10 membered bicyclic heteroaryl group having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulphur. Exemplary such R 1 , R 2 , R 3 , R 4 , R 5  and R 6  groups include -Omethyl, -Oethyl, -Opropyl, -Oisopropyl, -Ocyclopropyl, -Obutyl, -Oisobutyl, -Ocyclobutyl, -Ophenyl, -Opyridyl, -Omorpholinyl, -Opyrrolidinyl, -Oimidazolyl, and -Ocyclohexyl. 
         [0106]    In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently R wherein each R is a C 1-6  aliphatic group substituted with one or more halogens. In some embodiments, each R is C 1-6  aliphatic substituted with one, two, or three halogens. In other embodiments, each R is a perfluorinated C 1-6  aliphatic group. Examples of fluorinated hydrocarbons represented by R 1 , R 2 , R 3 , R 4 , R 5  and R 6  include mono-, di-, tri, or perfluorinated methyl, ethyl, propyl, butyl, or phenyl. In some embodiments, each of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is trifluoromethyl, trifluoroethyl, or trifluoropropyl. 
         [0107]    In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently a polyether. Examples of polyethers represented by R 1 , R 2 , R 3 , R 4 , R 5  and R 6  include poly(ethylene oxide), poly(difluoromethyl ethylene oxide), poly(trifluoromethyl ethylene oxide), poly(propylene oxide), poly(difluoromethyl propylene oxide), poly(propylene oxide), poly(trifluoromethyl propylene oxide), poly(butylene oxide), poly(tetramethylene ether glycol), poly(tetrahydrofuran), poly(oxymethylene), poly(ether ketone), poly(etherether ketone) and copolymers thereof. 
         [0108]    In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently a polyester. Examples of polyesters represented by R 1 , R 2 , R 3 , R 4 , R 5  and R 6  include poly(ethylene terephthalate) (PET), poly(ethylene terephthalate ionomer) (PETI), poly(ethylene naphthalate) (PEN), poly(methylene naphthalate) (PTN), poly(butylene teraphalate) (PBT), poly(butylene naphthalate) (PBN), polycarbonate. 
         [0109]    In certain embodiments, one or more of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently a fluoropolymer. Examples of fluoropolymers represented by R 1 , R 2 , R 3 , R 4 , R 5  and R 6  include poly(tetrafluoroethylene), poly(methyl di-fluoroethyl siloxane), poly(methyl tri-fluoroethyl siloxane), poly(phenyl di-fluoroethyl siloxane). 
         [0110]    In some embodiments, R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently hydrogen, hydroxyl, carboxylic acids such as methanoic or ethanoic acid as well as methacrylic acid and other acrylic acids. Alkyl or aryl hydrocarbons such as methyl, ethyl, propyl, butyl, phenyl and ethers thereof. Fluorinated hydrocarbons such as mono-, di-, tri, or perfluorinated methyl, ethyl, propyl, butyl, phenyl. Polyether such as Poly(ethylene oxide), poly(difluoromethyl ethylene oxide), poly(trifluoromethyl ethylene oxide), poly(propylene oxide), poly(difluoromethyl propylene oxide), poly(propylene oxide), poly(trifluoromethyl propylene oxide), poly(butylene oxide), poly(tetramethylene ether glycol), poly(tetrahydrofuran), poly(oxymethylene), poly(ether ketone), poly(etherether ketone) and copolymers thereof. Polyesters such as Poly(ethylene terephthalate) (PET), poly(ethylene terephthalate ionomer) (PETI), poly(ethylene naphthalate) (PEN), poly(methylene naphthalate) (PTN), Poly(Butylene Teraphalate) (PBT), poly(butylene naphthalate) (PBN), polycarbonate and .fluoropolymer such as Poly(tetrafluoroethylene), poly(methyl di-fluoroethyl siloxane), poly(methyl tri-fluoroethyl siloxane), poly(phenyl di-fluoroethyl siloxane) 
         [0111]    In some embodiments, m and p are between 2 and 50 and n is between 2 and 20. In certain embodiments, m and o are between 2 and 30 and n is between 2 and 20. 
         [0112]    As defined generally above, each of L 1  and L 2  is independently a bivalent C 1-20  hydrocarbon chain wherein 1-4 methylene units of the hydrocarbon chain are optionally and independently replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)N(R)—, —N(R)C(O)—, —SO 2 —, —SO 2 N(R)—, —N(R)SO 2 —, —OC(O)—, —C(O)O—, or a bivalent cycloalkylene, arylene, heterocyclene, or heteroarylene, provided that neither of L 1  nor L 2  comprises a urea or urethane moiety. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-20  alkylene chain. In certain embodiments, each of L 1  and L 2  is independently a bivalent C 1-10  alkylene chain. In certain embodiments, each of L 1  and L 2  is independently a bivalent C 1-6  alkylene chain. In certain embodiments, each of L 1  and L 2  is independently a bivalent C 1-4  alkylene chain. Exemplary such L 1  and L 2  groups include methylene, ethylene, propylene, butylene or higher bivalent alkanes. 
         [0113]    In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-20  alkylene chain wherein one methylene unit of the chain is replaced by —O—. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-10  alkylene chain wherein one methylene unit of the chain is replaced by —O—. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-6  alkylene chain wherein one methylene unit of the chain is replaced by —O—. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-4  alkylene chain wherein one methylene unit of the chain is replaced by —O—. Exemplary such L 1  and L 2  groups include —OCH 2 —, —OCH 2 CH 2 —, —OCH 2 CH 2 CH 2 —, —OCH 2 CH 2 CH 2 CH 2 —, or higher bivalent alkylene ethers. 
         [0114]    In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-20  alkylene chain wherein at least one methylene unit of the chain is replaced by —O— and at least one methylene unit of the chain is replaced by a bivalent arylene. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-10  alkylene chain wherein at least one methylene unit of the chain is replaced by —O— and at least one methylene unit of the chain is replaced by a bivalent arylene. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-6  alkylene chain wherein at least one methylene unit of the chain is replaced by —O— and at least one methylene unit of the chain is replaced by a bivalent arylene. In some embodiments, each of L 1  and L 2  is independently a bivalent C 1-4  alkylene chain wherein at least one methylene unit of the chain is replaced by —O— and at least one methylene unit of the chain is replaced by a bivalent arylene. Exemplary such L 1  and L 2  groups include —OCH 2 -phenylene-, —OCH 2 CH 2 -phenylene-, —OCH 2 CH 2 -phenylene-CH 2 —, —OCH 2 CH 2 CH 2 CH 2 -phenylene-, and the like. 
         [0115]    One of ordinary skill in the art would understand that a polyurethane results from the reaction of a diisocyanate and a hydroxyl group. Similarly, a polyurea results from the reaction of a diisocyanate and an amine. Each of these reactions is depicted below. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0116]    Thus, it is readily apparent that provided compounds of formula I can be functionalized with end groups suitable for forming urethane and/or urea linkages. In certain embodiments, the present invention provides a compound of formula II: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein:
 
each of R x  and R y  is independently —OH, —NH 2 , a protected hydroxyl or a protected amine;
 
each of X and Y is independently a polymer or co-polymer chain formed from one or more of a polyether, a polyester, a polycarbonate, and a fluoropolymer;
 
each of R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is independently selected from one or more of R, OR, —CO 2 R, a fluorinated hydrocarbon, a polyether, a polyester or a fluoropolymer;
 
each R is independently hydrogen, an optionally substituted C 1-20  aliphatic group, or an optionally substituted group selected from phenyl, 8-10 membered bicyclic aryl, a 4-8 membered monocyclic saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulphur, or 5-6 membered monocyclic or 8-10 membered bicyclic heteroaryl group having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
 
each of m n and p is independently 2 to 100; and
 
each of L 1  and L 2  is independently a bivalent C 1-20  hydrocarbon chain wherein 1-4 methylene units of the hydrocarbon chain are optionally and independently replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)N(R)—, —N(R)C(O)—, —SO 2 —, —SO 2 N(R)—, —N(R)SO 2 —, —OC(O)—, —C(O)O—, or a bivalent cycloalkylene, arylene, heterocyclene, or heteroarylene, provided that neither of L 1  nor L 2  comprises a urea or urethane moiety.
 
         [0117]    In some embodiments, each of X, Y, m, n, p, L 1 , L 2 , R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  is as defined and described herein. 
         [0118]    As defined generally above, each of R x  and R y  is independently —OH, —NH 2 , a protected hydroxyl or a protected amine. In some embodiments, both of R x  and R y  are —OH. In other embodiments, both of R x  and R y  are —NH 2 . In some embodiments one of R x  and R y  is —OH and the other is —NH 2 . 
         [0119]    In some embodiments, each of R x  and R y  is independently a protected hydroxyl or a protected amine. Such protected hydroxyl and protected amine groups are well known to one of skill in the art and include those described in detail in  Protecting Groups in Organic Synthesis , T. W. Greene and P. G. M. Wuts, 3rd edition, John Wiley &amp; Sons, 1999, the entirety of which is incorporated herein by reference. Exemplary protected amines include methyl carbamate, ethyl carbamante, 9-fluorenylmethyl carbamate (Fmoc), 9-(2-sulfo)fluorenylmethyl carbamate, 9-(2,7-dibromo)fluoroenylmethyl carbamate, 2,7-di-t-butyl-[9-(10,10-dioxo-10,10,10,10-tetrahydrothioxanthyl)]methyl carbamate (DBD-Tmoc), 4-methoxyphenacyl carbamate (Phenoc), 2,2,2-trichloroethyl carbamate (Troc), 2-trimethylsilylethyl carbamate (Teoc), 2-phenylethyl carbamate (hZ), 1-(1-adamantyl)-1-methylethyl carbamate (Adpoc), 1,1-dimethyl-2-haloethyl carbamate, 1,1-dimethyl-2,2-dibromoethyl carbamate (DB-t-BOC), 1,1-dimethyl-2,2,2-trichloroethyl carbamate (TCBOC), 1-methyl-1-(4-biphenylyl)ethyl carbamate (Bpoc), 1-(3,5-di-t-butylphenyl)-1-methylethyl carbamate (t-Bumeoc), 2-(2′- and 4′-pyridyl)ethyl carbamate (Pyoc), 2-(N,N-dicyclohexylcarboxamido)ethyl carbamate, t-butyl carbamate (BOC), 1-adamantyl carbamate (Adoc), vinyl carbamate (Voc), allyl carbamate (Alloc), 1-isopropylallyl carbamate (Ipaoc), cinnamyl carbamate (Coc), 4-nitrocinnamyl carbamate (Noc), 8-quinolyl carbamate, N-hydroxypiperidinyl carbamate, alkyldithio carbamate, benzyl carbamate (Cbz), p-methoxybenzyl carbamate (Moz), p-nitobenzyl carbamate, p-bromobenzyl carbamate, p-chlorobenzyl carbamate, 2,4-dichlorobenzyl carbamate, 4-methylsulfinylbenzyl carbamate (Msz), 9-anthrylmethyl carbamate, diphenylmethyl carbamate, 2-methylthioethyl carbamate, 2-methylsulfonylethyl carbamate, 2-(p-toluenesulfonyl)ethyl carbamate, [2-(1,3-dithianyl)]methyl carbamate (Dmoc), 4-methylthiophenyl carbamate (Mtpc), 2,4-dimethylthiophenyl carbamate (Bmpc), 2-phosphonioethyl carbamate (Peoc), 2-triphenylphosphonioisopropyl carbamate (Ppoc), 1,1-dimethyl-2-cyanoethyl carbamate, m-chloro-p-acyloxybenzyl carbamate, p-(dihydroxyboryl)benzyl carbamate, 5-benzisoxazolylmethyl carbamate, 2-(trifluoromethyl)-6-chromonylmethyl carbamate (Tcroc), m-nitrophenyl carbamate, 3,5-dimethoxybenzyl carbamate, o-nitrobenzyl carbamate, 3,4-dimethoxy-6-nitrobenzyl carbamate, phenyl(o-nitrophenyl)methyl carbamate, phenothiazinyl-(10)-carbonyl derivative, N′-p-toluenesulfonylaminocarbonyl derivative, N′-phenylaminothiocarbonyl derivative, t-amyl carbamate, S-benzyl thiocarbamate, p-cyanobenzyl carbamate, cyclobutyl carbamate, cyclohexyl carbamate, cyclopentyl carbamate, cyclopropylmethyl carbamate, p-decyloxybenzyl carbamate, 2,2-dimethoxycarbonylvinyl carbamate, o-(N,N-dimethylcarboxamido)benzyl carbamate, 1,1-dimethyl-3-(N,N-dimethylcarboxamido)propyl carbamate, 1,1-dimethylpropynyl carbamate, di(2-pyridyl)methyl carbamate, 2-furanylmethyl carbamate, 2-iodoethyl carbamate, isoborynl carbamate, isobutyl carbamate, isonicotinyl carbamate, p-(p′-methoxyphenylazo)benzyl carbamate, 1-methylcyclobutyl carbamate, 1-methylcyclohexyl carbamate, 1-methyl-1-cyclopropylmethyl carbamate, 1-methyl-1-3,5-dimethoxyphenyl)ethyl carbamate, 1-methyl-1-(p-phenylazophenyl)ethyl carbamate, 1-methyl-1-phenylethyl carbamate, 1-methyl-1-(4-pyridyl)ethyl carbamate, phenyl carbamate, p-(phenylazo)benzyl carbamate, 2,4,6-tri-t-butylphenyl carbamate, 4-(trimethylammonium)benzyl carbamate, 2,4,6-trimethylbenzyl carbamate, formamide, acetamide, chloroacetamide, trichloroacetamide, trifluoroacetamide, phenylacetamide, 3-phenylpropanamide, picolinamide, 3-pyridylcarboxamide, N-benzoylphenylalanyl derivative, benzamide, p-phenylbenzamide, o-nitophenylacetamide, o-nitrophenoxyacetamide, acetoacetamide, (N′-dithiobenzyloxycarbonylamino)acetamide, 3-(p-hydroxyphenyl)propanamide, 3-(o-nitrophenyl)propan amide, 2-methyl-2-(o-nitrophenoxy)propanamide, 2-methyl-2-(o-phenylazophenoxy)propanamide, 4-chlorobutanamide, 3-methyl-3-nitrobutanamide, o-nitrocinnamide, N-acetylmethionine derivative, o-nitrobenzamide, o-(benzoyloxymethyl)benzamide, 4,5-diphenyl-3-oxazolin-2-one, N-phthalimide, N-dithiasuccinimide (Dts), N-2,3-diphenylmaleimide, N-2,5-dimethylpyrrole, N-1,1,4,4-tetramethyldisilylazacyclopentane adduct (STABASE), 5-substituted 1,3-dimethyl-1,3,5-triazacyclohexan-2-one, 5-substituted 1,3-dibenzyl-1,3,5-triazacyclohexan-2-one, 1-substituted 3,5-dinitro-4-pyridone, N-methylamine, N-allylamine, N-[2-(trimethylsilyl)ethoxy]methylamine (SEM), N-3-acetoxypropylamine, N-(1-isopropyl-4-nitro-2-oxo-3-pyroolin-3-yl)amine, quaternary ammonium salts, N-benzylamine, N-di(4-methoxyphenyl)methylamine, N-5-dibenzosuberylamine, N-triphenylmethylamine (Tr), N-[(4-methoxyphenyl)diphenylmethyl]amine (MMTr), N-9-phenylfluorenylamine (PhF), N-2,7-dichloro-9-fluorenylmethyleneamine, N-ferrocenylmethylamino (Fcm), N-2-picolylamino N′-oxide, N-1,1-dimethylthiomethyleneamine, N-benzylideneamine, N-p-methoxybenzylideneamine, N-diphenylmethyleneamine, N-[(2-pyridyl)mesityl]methyleneamine, N—(N′,N′-dimethylaminomethylene)amine, N,N′-isopropylidenediamine, N-p-nitrobenzylideneamine, N-salicylideneamine, N-5-chlorosalicylidene amine, N-(5-chloro-2-hydroxyphenyl)phenylmethyleneamine, N-cyclohexylidene amine, N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)amine, N-borane derivative, N-diphenylborinic acid derivative, N-[phenyl(pentacarbonylchromium- or tungsten)carbonyl]amine, N-copper chelate, N-zinc chelate, N-nitroamine, N-nitrosoamine, amine N-oxide, diphenylphosphinamide (Dpp), dimethylthiophosphinamide (Mpt), diphenylthiophosphinamide (Ppt), dialkyl phosphoramidates, dibenzyl phosphoramidate, diphenyl phosphoramidate, benzenesulfenamide, o-nitrobenzenesulfenamide (Nps), 2,4-dinitrobenzenesulfenamide, pentachlorobenzenesulfenamide, 2-nitro-4-methoxybenzenesulfenamide, triphenylmethylsulfenamide, 3-nitropyridinesulfenamide (Npys), p-toluenesulfonamide (Ts), benzenesulfonamide, 2,3,6,-trimethyl-4-methoxybenzenesulfonamide (Mtr), 2,4,6-trimethoxybenzenesulfonamide (Mtb), 2,6-dimethyl-4-methoxybenzenesulfonamide (Pme), 2,3,5,6-tetramethyl-4-methoxybenzenesulfonamide (Mte), 4-methoxybenzenesulfonamide (Mbs), 2,4,6-trimethylbenzenesulfonamide (Mts), 2,6-dimethoxy-4-methylbenzenesulfonamide (iMds), 2,2,5,7,8-pentamethylchroman-6-sulfonamide (Pmc), methanesulfonamide (Ms), β-trimethylsilylethanesulfonamide (SES), 9-anthracenesulfonamide, 4-(4′,8′-dimethoxynaphthylmethyl)benzenesulfonamide (DNMBS), benzylsulfonamide, trifluoromethylsulfonamide, and phenacylsulfonamide. 
         [0120]    Exemplary hydroxyl protecting groups include methyl, methoxylmethyl (MOM), methylthiomethyl (MTM), t-butylthiomethyl, (phenyldimethylsilyl)methoxymethyl (SMOM), benzyloxymethyl (BOM), p-methoxybenzyloxymethyl (PMBM), (4-methoxyphenoxy)methyl (p-AOM), guaiacolmethyl (GUM), t-butoxymethyl, 4-pentenyloxymethyl (POM), siloxymethyl, 2-methoxyethoxymethyl (MEM), 2,2,2-trichloroethoxymethyl, bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl (SEMOR), tetrahydropyranyl (THP), 3-bromotetrahydropyranyl, tetrahydrothiopyranyl, 1-methoxycyclohexyl, 4-methoxytetrahydropyranyl (MTHP), 4-methoxytetrahydrothiopyranyl, 4-methoxytetrahydrothiopyranyl S,S-dioxide, 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl (CTMP), 1,4-dioxan-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl, 2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl, 1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl, 1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-(phenylselenyl)ethyl, t-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl, benzyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl, p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, p-phenylbenzyl, 2-picolyl, 4-picolyl, 3-methyl-2-picolyl N-oxido, diphenylmethyl, p,p′-dinitrobenzhydryl, 5-dibenzosuberyl, triphenylmethyl, α-naphthyldiphenylmethyl, p-methoxyphenyldiphenylmethyl, di(p-methoxyphenyl)phenylmethyl, tri(p-methoxyphenyl)methyl, 4-(4′-bromophenacyloxyphenyl)diphenylmethyl, 4,4′,4″-tris(4,5-dichlorophthalimidophenyl)methyl, 4,4′,4″-tris(levulinoyloxyphenyl)methyl, 4,4′,4″-tris(benzoyloxyphenyl)methyl, 3-(imidazol-1-yl)bis(4′,4″-dimethoxyphenyl)methyl, 1,1-bis(4-methoxyphenyl)-1′-pyrenylmethyl, 9-anthryl, 9-(9-phenyl)xanthenyl, 9-(9-phenyl-10-oxo)anthryl, 1,3-benzodithiolan-2-yl, benzisothiazolyl S,S-dioxido, trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), dimethylisopropylsilyl (IPDMS), diethylisopropylsilyl (DEIPS), dimethylthexylsilyl, t-butyldimethylsilyl (TBDMS), t-butyldiphenylsilyl (TBDPS), tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl, diphenylmethylsilyl (DPMS), t-butylmethoxyphenylsilyl (TBMPS), formate, benzoylformate, acetate, chloroacetate, dichloroacetate, trichloroacetate, trifluoroacetate, methoxyacetate, triphenylmethoxyacetate, phenoxyacetate, p-chlorophenoxyacetate, 3-phenylpropionate, 4-oxopentanoate (levulinate), 4,4-(ethylenedithio)pentanoate (levulinoyldithioacetal), pivaloate, adamantoate, crotonate, 4-methoxycrotonate, benzoate, p-phenylbenzoate, 2,4,6-trimethylbenzoate (mesitoate), alkyl methyl carbonate, 9-fluorenylmethyl carbonate (Fmoc), alkyl ethyl carbonate, alkyl 2,2,2-trichloroethyl carbonate (Troc), 2-(trimethylsilyl)ethyl carbonate (TMSEC), 2-(phenylsulfonyl)ethyl carbonate (Psec), 2-(triphenylphosphonio) ethyl carbonate (Peoc), alkyl isobutyl carbonate, alkyl vinyl carbonate alkyl allyl carbonate, alkyl p-nitrophenyl carbonate, alkyl benzyl carbonate, alkyl p-methoxybenzyl carbonate, alkyl 3,4-dimethoxybenzyl carbonate, alkyl o-nitrobenzyl carbonate, alkyl p-nitrobenzyl carbonate, alkyl S-benzyl thiocarbonate, 4-ethoxy-1-napththyl carbonate, methyl dithiocarbonate, 2-iodobenzoate, 4-azidobutyrate, 4-nitro-4-methylpentanoate, o-(dibromomethyl)benzoate, 2-formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl, 4-(methylthiomethoxy)butyrate, 2-(methylthiomethoxymethyl)benzoate, 2,6-dichloro-4-methylphenoxyacetate, 2,6-dichloro-4-(1,1,3,3-tetramethylbutyl)phenoxyacetate, 2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate, isobutyrate, monosuccinoate, (E)-2-methyl-2-butenoate, o-(methoxycarbonyl)benzoate, α-naphthoate, nitrate, alkyl N,N,N′,N′-tetramethylphosphorodiamidate, alkyl N-phenylcarbamate, borate, dimethylphosphinothioyl, alkyl 2,4-dinitrophenylsulfenate, sulfate, methanesulfonate (mesylate), benzylsulfonate, and tosylate (Ts). For protecting 1,2- or 1,3-diols, the protecting groups include methylene acetal, ethylidene acetal, 1-t-butylethylidene ketal, 1-phenylethylidene ketal, (4-methoxyphenyl)ethylidene acetal, 2,2,2-trichloroethylidene acetal, acetonide, cyclopentylidene ketal, cyclohexylidene ketal, cycloheptylidene ketal, benzylidene acetal, p-methoxybenzylidene acetal, 2,4-dimethoxybenzylidene ketal, 3,4-dimethoxybenzylidene acetal, 2-nitrobenzylidene acetal, methoxymethylene acetal, ethoxymethylene acetal, dimethoxymethylene ortho ester, 1-methoxyethylidene ortho ester, 1-ethoxyethylidine ortho ester, 1,2-dimethoxyethylidene ortho ester, α-methoxybenzylidene ortho ester, 1-(N,N-dimethylamino)ethylidene derivative, α-(N,N′-dimethylamino)benzylidene derivative, 2-oxacyclopentylidene ortho ester, di-t-butyl silylene group (DTBS), 1,3-(1,1,3,3-tetraisopropyldisiloxanylidene) derivative (TIPDS), tetra-t-butoxydisiloxane-1,3-diylidene derivative (TBDS), cyclic carbonates, cyclic boronates, ethyl boronate, and phenyl boronate. 
         [0121]    One of ordinary skill in the art will appreciate that the choice of hydroxyl and amine protecting groups can be such that these groups are removed at the same time (e.g., when both protecting groups are acid labile or base labile). Alternatively, such groups can be removed in a step-wise fashion (e.g., when one protecting group is removed first by one set of removal conditions and the other protecting group is removed second by a different set of removal conditions). Such methods are readily understood by one of ordinary skill in the art. 
         [0122]    In certain embodiments, the present invention provides a compound of any of formulae II-a, II-b, II-c, and II-d: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein each of X, Y, m, n, p, L 1 , L 2 , R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is as defined and described herein. 
         [0123]    Exemplary triblock copolymers of the present invention are set forth below: 
         [0000]    
       
                 
         
             
             
         
       
       
                 
         
             
             
         
       
     
         [0000]    wherein each of m, n, and p is as defined and described herein. 
         [0124]    In some embodiments, the present invention provides a polymer foam, comprising:
       (a) one or more triblock copolymers of formula I:       
 
         [0000]    
       
                 
         
             
             
         
       
       
         
           
             wherein each of X, Y, m, n, p, L 1 , L 2 , R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is as defined and described herein; and 
             (b) wherein the copolymers are chemically interspersed (bound) between urethane and/or urea linkages (i.e., at the bond designated with          ). 
           
         
       
     
         [0128]    The invention further provides a pre-formed soft segment of the formula I as defined above. In some embodiments, the present invention provides a polyurethane/urea foam comprising a soft segment triblock copolymer of formula I. 
         [0129]    In some embodiments, the present invention provides a viscoelastic biostable water blown foam, comprising:
       (a) one or more triblock copolymers of formula I:       
 
         [0000]    
       
                 
         
             
             
         
       
       
         
           
             wherein each of X, Y, m, n, p, L 1 , L 2 , R 1 , R 2 , R 3 , R 4 , R 5  and R 6  is as defined and described herein; and 
             (b) wherein the copolymers are chemically interspersed (bound) between urethane and/or urea linkages (i.e., at the bond designated with          ). 
           
         
       
     
         [0133]    It has been surprisingly found that polyurethanes and/or polyureas comprising a triblock copolymer of the present invention are stable to gastric fluid. Such polyurethanes and polyureas prepared using triblock copolymers of the present invention are viscoelastic and stable to gastric fluid. In some embodiments, a provided viscoelastic material is a foam. 
         [0134]    In certain embodiments, a provided biostable foam is stable to gastric fluid. In some embodiments, a provided biostable foam is stable to gastric fluid for at least one year. In some embodiments, a provided biostable foam is stable to gastric fluid for at least 3 months, for at least 4 months, for at least 5 months, for at least 6 months, for at least 7 months, for at least 8 months, for at least 9 months, for at least 10 months, for at least 11 months, or for at least one year. Methods for determining stability of a provided biostable foam are known in the art utilizing simulated gastric fluid and include those described in detail in the Exemplification, infra. 
         [0135]    In some embodiments, a provided viscoelastic foam, comprising a triblock copolymer of the present invention, is characterized in that the foam takes up less than about 30% by weight of water at equilibrium. In certain embodiments, a provided viscoelastic foam takes up less than about 5%, less than about 10%, less than about 15%, less than about 20%, less than about 25%, or less than about 30% by weight of water at equilibrium. One of ordinary skill in the art will appreciate that such chemical stability (i.e., in gastric fluid and therefore at very low pH) and hyrophobicity (i.e., water uptake of less than about 30% by weight) are characterisitics that differ dramatically from known siloxane polymers that are utilized in, e.g., the manufacture of contact lenses. For example, siloxane polymer that are utilized in, e.g., the manufacture of contact lenses require a water uptake of 50-120%. 
         [0136]    As described above, the present invention provides a viscoelastic foam comprising a triblock copolymer of the present invention. It was suprisingly found that a provided foam has a high elongation capacity and the ability to recover very slowly following elongation. Indeed, it was found that a provided viscoelastic foam has an elongation capacity of about 200-1200%. In some embodiments, a provided viscoelastic foam has an elongation capacity of about 500%. 
         [0137]    In some embodiments, a provided viscoelastic foam has a tensile strength of about 0.1 to about 1.0 MPa. In certain embodiments, a provided viscoelastic foam has a tensile strength of about 0.25 to about 0.5 MPa. 
         [0138]    In some embodiments, a provided viscoelastic foam has a Young&#39;s Modulus of about 0.1 to about 0.6 MPa. In certain embodiments, a provided viscoelastic foam has a Young&#39;s Modulus of about 0.1 to about 0.5 MPa. 
         [0139]    One of ordinary skill in the art will appreciate that, depending upon the physical characteristics required for a particular use of a provided foam, a foam of varying densities can be prepared. For example, a valve having a thinner wall would require a foam having a higher density than a similar valve having a thicker wall in order to result in each valve having a similar physical characteristic (e.g., tensile strength, and the like). Thus, in certain embodiments, a provided viscoelastic foam has a density of 0.1 to 1.5 g/cm 3 . In certain embodiments, a provided viscoelastic foam has a density of 0.3 to 1.2 g/cm 3 . In certain embodiments, a provided viscoelastic foam has a density of 0.8 to 0.9 g/cm 3 . In some embodiments, a provided viscoelastic foam has a density of 0.5 to 0.6 g/cm 3 . 
         [0140]    In certain embodiments, the present invention provides polyether-siloxane and polyether-fluorosiloxane polyurethane materials with a greatly reduced number of weak-links as illustrated by  FIG. 2  and  FIG. 3 . This was achieved by preforming the soft segment prior to the polyurethane reaction. In the examples below a triblock copolymer based on polydimethyl siloxane and polypropylene oxide was used but it will be appreciated that other triblock copolymers such as those formed from polysiloxanes and poly(ethylene oxide), poly(difluoromethyl ethylene oxide), poly(trifluoromethyl ethylene oxide), poly(propylene oxide), poly(difluoromethyl propylene oxide), poly(propylene oxide), poly(trifluoromethyl propylene oxide), poly(butylene oxide), poly(tetramethylene ether glycol), poly(tetrahydrofuran), poly(oxymethylene), poly(ether ketone), poly(etherether ketone) and copolymers thereof, poly(dimethylsiloxane), poly(diethylsiloxane) and higher alkyl siloxanes, poly(methyl phenyl siloxane), poly(diphenyl siloxane), poly(methyl di-fluoroethyl siloxane), poly(methyl tri-fluoroethyl siloxane), poly(phenyl di-fluoroethyl siloxane), poly(phenyl tri-fluoroethyl siloxane) and copolymers thereof, poly(ethylene terephthalate) (PET), poly(ethylene terephthalate ionomer) (PETI), poly(ethylene naphthalate) (PEN), poly(methylene naphthalate) (PTN), poly(butylene teraphalate) (PBT), poly(butylene naphthalate) (PBN) and polycarbonate could be used. 
         [0141]    Referring to  FIG. 2 , copolymers of the form ABA, ABC and BAB were produced from homopolymers of polysiloxane and polypropylene oxide which were covalently linked using bonds less labile than urethane/urea. The molecular weight and chemical charateristics of such homopolymers were tailored to achieve a pre-soft-segment with the appropriate balance of hydrophilicity/hydrophobicity. Without wishing to be bound by any particular theory, it is believe that by using a non-urethane linked tri-block copolymer instead of the constiuent homopolymers as soft segments that the mechanical characteristics and hydrolytic stability of the resulting material is substantially improved. 
         [0142]    In some embodiments, the present invention provides a foam comprising a copolymer of the present invention. Such foams offer specific advantages over solid elastomers, especially for gastrointestinal device applications. These advantages include enhanced biostability in the gastric environment, compressibility, viscoelasticity and high ‘surface area to volume ratio’. The foam formulations of the invention can mimic mechanical characteristics of the native gastrointestinal tissue. 
         [0143]    A biostable water blown foam was prepared from heterogenous reagents. 
         [0144]    The prior art describes polyurethane foams that are prepared by the sequential reaction of polymer chains to one another resulting in a high molecular weight solid material. In all cases the polymeric precursors described in the art are linked together by urethane/urea linkages as illustrated in  FIG. 1 . However, each urethane/urea linkage is a possible site for degradation. 
         [0145]    In the invention we have prepared a biostable polyurethane/urea foam with much fewer ‘weak links’ by using co-polymer precursors as shown in  FIG. 2 . 
         [0146]    Polyurethane reactions have historically been carried out in a single phase due to ease of processing. However, we have made novel materials by combining physically heterogenous reaction pre-cursors together to form a stable two-phase dispersion (&#39;water-in-oil&#39;) which was then reacted to form a foam. 
       EXEMPLIFICATION 
       [0147]    In two specific examples X and Y are both polyethers namely poly(propylene oxide) (PPO). These were formulated into copolymers with poly(dimethylsiloxane) (PDMS) and poly(trifluoropropyl methylsiloxane) respectively in varying ratios as described by the following formulae: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0148]    The formulations contained a number of other components including: 
       Branching Agent—DEOA 
       [0149]    
       
                 
         
             
             
         
       
     
         [0150]    Diethanolamine (DEOA) is used as a branching agent although it is sometimes known as a crosslinking agent. The molecular weight of DEOA is 105.14 g/mol. The effect of the DEOA is to influence softness and elasticity of the end polymer. 
       Gelling Catalyst—Bismuth Neodecanoate (BICAT) 
       [0151]    
       
                 
         
             
             
         
       
     
         [0152]    Bismuth neodecanoate is supplied as BiCat 8108M from Shepherd. It has a molecular weight of 722.75 g/mol. This catalyst is used to facilitate the complete reaction between isocyanate and hydroyl or amine functional groups. 
       Blowing Catalyst—DABCO 33-lv 
       [0153]    
       
                 
         
             
             
         
       
     
         [0154]    DABCO is a common blowing catalyst for reaction between NCO and H 2 O. It has a molecular weight of 112.17 g/mol. This catalyst has the effect, in combination with H 2 O, of manipulating the foam rise characteristics. 
       Example 1 
     Synthesis of Aliphatic Linked Fluorosiloxane Based Triblock Copolymer Pre-Soft-Segment 
       [0155]    This is a 2 step process. In the first step silanol terminated poly(trifluoropropyl methyl siloxane) is converted into its dihydride derivative. In the next step, this dihydride derivative is reacted with the allyl terminated poly(propylene glycol). 
         [0156]    The synthetic procedure is as follows: 
       Step 1: 
       [0157]    
       
                 
         
             
             
         
       
     
         [0158]    To a 4 neck separable flask fitted with mechanical stirrer, was added 40 g of Silanol terminated poly(trifluoropropyl methylsiloxane) (FMS-9922 from Gelest Inc.) and this was mixed with 50 ml of toluene and fitted with a continuous flush of Nitrogen. To the reaction mixture 7.57 g of dimethyl chlorosilane (DMCS, from Sigma Aldrich) was added slowly over about 20 minutes keeping the temperature of the mixture constant at 30° C. With each addition of dimethyl chlorosilane, the mixture became hazy but cleared in a short period of time. Once the addition of dimethyl chlorosilane was complete, the mixture was heated to 90° C. for 3 hours. The reaction was then washed with excess water several times to reduce the acidity of the mixture. The resulting mixture was dried over silica gel, filtered and vacuumed to remove solvent and traces of water at 65° C. overnight. A clear fluid was then obtained with a very strong Si—H band in infra red spectroscopy (IR) at 2130 cm −1 , which confirms the reaction. GPC analysis showed the molecular weight to be 1200 g/mol. 
       Step 2: 
       [0159]    
       
                 
         
             
             
         
       
     
         [0160]    To 90 ml of reagent grade toluene in a 4 neck separable flask fitted with mechanical stirrer, 46.67 g of Allyl terminated poly(propylene glycol) (MW=700 g/mol, Jiangsu GPRO Group Co.) was added and then heated to reflux. Then 40 g of Hydride terminated FMS-9922 was dissolved in 50 ml of reagent grade toluene and the temperature raised to around 90° C. To the reaction mixture 2 drops of hexachloroplatinic(IV) acid (0.01M H 2 PtCl 6  from Sigma) solution in isopropanol (by Merck) was then added. After this catalyst solution had been added, the mixture was refluxed for 1 hour and the solvent distilled off in order to get the final product. The reaction was followed by H-NMR and gel permeation chromatography (GPC) confirmed the final molecular weight to be 2700 g/mol. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Resulting polymer block ratios 
               
               
                 Stoiciometric ratios for reaction product: 
               
             
          
           
               
                   
                 Polymer block 
               
             
          
           
               
                   
                 PO 
                 F—SiO 
                 PO 
               
               
                   
                 m 
                 n 
                 p 
               
               
                   
                   
               
             
          
           
               
                   
                 Ratio 
                 11 
                 9.7 
                 11 
               
               
                   
                   
               
             
          
         
       
     
       Example 2 
     Synthesis of Aliphatic Linked Dimethylsiloxane Based Triblock Copolymer Pre-Soft-Segment 
       [0161]    To 130 ml of reagent grade toluene in a separable flask fitted with a mechanical stirrer, was added 64 g of allyl terminated poly(propylene glycol) (MW=700 g/mol, Jiangsu GPRO Co.) and both were mixed and heated to reflux. Then 40 g of hydride terminated poly(dimethyl siloxane) (Silmer H Di 10 by Siltech Corp.) was dissolved in 50 ml reagent grade toluene and the temperature raised to around 90° C. To this reaction mixture 2 drops of hexachloroplatinic(IV) acid (0.01M H 2 PtCl 6  from Sigma) solution in isopropanol was added. After this catalyst solution was added, the mixture was refluxed for 1 hour and then the solvent was distilled off in order to get the final product. The reaction was followed with H-NMR and gel permeation chromatography (GPC) confirmed the final molecular weight of the product to be 2300 g/mol. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Polymer block ratios 
               
               
                 Stoiciometric ratios for reaction product: 
               
             
          
           
               
                   
                 Polymer block 
               
             
          
           
               
                   
                 PO 
                 SiO 
                 PO 
               
               
                   
                 m 
                 n 
                 p 
               
               
                   
                   
               
             
          
           
               
                   
                 Ratio 
                 11 
                 11 
                 11 
               
               
                   
                   
               
             
          
         
       
     
       Example 3 
     Synthesis of Aromatic Linked Siloxane Based Triblock Copolymer Pre-Soft-Segment 
       [0162]    
       
                 
         
             
             
         
       
     
         [0163]    To a 100 ml separable flask fitted with a mechanical stirrer, 15 g of hydroxy terminated polydimethyl siloxane (DMS-S14 from Gelest Inc.) was added along with 5.36 g of di-chloro p-xylene (from Sigma) and 0.0089 g of Copper(II) acetylacetonate (Cu(Acac) 2  from Sigma). The reaction mixture was refluxed at 110° C. for 5 hrs. At this point, 19.77 g of hydroxy terminated poly(propylene glycol) (from Sigma) was added dropwise and the reaction mixture was then refluxed for another 15 hr. The progress of reaction was followed by  1 H-NMR and the final molecular weight, determined by gel permeation chromatography (GPC), was 3000 g/mol. 
         [0164]    H-NMR analysis: Solvent used for  1 H-NMR analysis is CDCl 3 . 
         [0165]    Aromatic H=7.25-7.45 ppm, —CH 2 =4.5-4.6 ppm, —CH 3  (of PPO)=1-1.4 ppm, —CH 2  (of PPO)=3.2-3.8 ppm, —OH (of PPO)=3.8-4 ppm, —CH 3 (silanol)=0.5-0.8 ppm. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Resulting polymer block ratios 
               
               
                 Stoiciometric ratios for reaction product: 
               
             
          
           
               
                   
                 Polymer block 
               
             
          
           
               
                   
                 PO 
                 SiO 
                 PO 
               
               
                   
                 m 
                 n 
                 p 
               
               
                   
                   
               
             
          
           
               
                   
                 Ratio 
                 14 
                 15.5 
                 14 
               
               
                   
                   
               
             
          
         
       
     
       Example 4 
     Synthesis of Aromatic Linked Fluorosiloxane Based Triblock Copolymer Pre-Soft-Segment 
       [0166]    
       
                 
         
             
             
         
       
     
         [0167]    To a 100 ml separable flask fitted with a mechanical stirrer, 15 g of hydroxy terminated polytrifluoromethyl siloxane (FMS-9922, Gelest inc.) was added along with 5.9 g of di-chloro p-xylene and 0.0098 g of copper(II) acetylacetonate (Cu(Acac) 2  from Sigma). The reaction mixture was refluxed at 110° C. for 5 hrs. At this point, 21.75 g of hydroxy terminated poly(propylene glycol) (from Sigma) was added dropwise to the reaction mixture. The reaction was refluxed for another 15 hr. The progress of reaction was followed by  1 H-NMR analysis and the molecular weight, determined by gel permeation chromatography (GPC), was 3100 g/mol. 
         [0168]      1 H-NMR analysis: Solvent used for H-NMR analysis is CDCl 3 . 
         [0169]    Aromatic  1 H=7.25-7.45 ppm, —CH 2 =4.5-4.6 ppm, —CH 3  (of PPO)=1-1.4 ppm, —CH 2  (of PPO)=3.2-3.8 ppm, —OH (of PPO)=3.8-4 ppm, —CH 3 (silanol)=0.5-0.8 ppm. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Polymer block ratios 
               
               
                 Stoiciometric ratios for reaction product: 
               
             
          
           
               
                   
                 Polymer block 
               
             
          
           
               
                   
                 PO 
                 FSiO 
                 PO 
               
               
                   
                 m 
                 n 
                 p 
               
               
                   
                   
               
             
          
           
               
                   
                 Ratio 
                 14 
                 9.2 
                 14 
               
               
                   
                   
               
             
          
         
       
     
       Example 5 
     Preparation of Water Blown Foam 
       [0170]    The pre-soft segments prepared can be described as having polymer block ratios which are numerically represented by the letters m, n and o for the constituents PO/SiO/PO respectively. The triblock copolymers prepared in Examples 1 and 2 with specific m, n, o ratios were formulated into polyurethane/urea foams as illustrated by Table 7. 
         [0171]    The process for preparing the foam was a two-step procedure. The following describes the method of manufacture of the first product in Table 7. The same procedure was used to prepare other foams as described by Table 8.
   Step 1) Firstly a mixture was made with 0.041 g of DABCO LV-33 (Airproducts), 0.120 g of bismuth neodecanoate (Bicat 8108M from Shepherd chemicals), 0.467 g of diethanol amine (DEOA, from Sigma), 7.917 g of synthesized block copolymer, 0.200 g water and 0.1 g of surfactant (Niax L-618 from Airproducts) in a plastic flat bottomed container. This is then thoroughly mixed manually for 30 sec until a homogenous mixture was obtained.   Step 2) To the above mixture, 15 g of a diisocyanate prepolymer (PPT 95A Airproducts) was added. This was then thoroughly mixed by a mechanical stirrer for about 5 seconds. The material was then molded and cured at 70° C. for 2.5 hours and post cured at 50° C. for another 3 hours.   
 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Formulation details for foam 
               
             
          
           
               
                   
                 Polymer block 
                   
                   
                   
                   
               
               
                 Formulation 
                 (PO/SiO/PO) 
               
               
                 Identification 
                 Ratio m:n:p 
                 DABCO 
                 BICAT 
                 DEOA 
                 H 2 O 
               
               
                   
               
               
                 VF230209A 
                 11:11:11 
                 0.0325 
                 0.015 
                 0.40 
                 1.0 
               
               
                 VF090309B 
                 11:9:11 
                 0.0325 
                 0.015 
                 0.40 
                 1.0 
               
               
                   
               
             
          
         
       
     
       Example 6 
     Comparative Example of Formulation of Water Blown Foam from Triblock Copolymer Pre-Soft Segment and Individual Homopolymers 
       [0174]    Polyurethane/urea polymer foams from Example 5 were compared to foams made from the stoiciometric equivalent homopolymer soft segments. The foams with homopolymer based soft segments (VF130309 and VF190309) shown in  FIG. 4  were produced as follows (VF130309):
   Step 1) Firstly a mixture was made with 0.041 g of DABCO LV-33 (Airproducts), 0.120 g of bismuth neodecanoate (Bicat 8108M from Shepherd chemicals), 0.467 g of diethanol amine (DEOA, from Sigma), 3.056 g of poly(dimethyl siloxane) diol (DMS-s14 Gelest Inc.), 1.633 g of polypropylene oxide (Mw=700 g/mol), 0.200 g water and 0.1 g of surfactant (Niax L-618 from Airproducts). These were added to a plastic flat bottomed container and were thoroughly mixed manually for 30 sec until a homogenous mixture was obtained.   Step 2) To the above mixture, 15 g of a diisocyanate prepolymer (PPT 95A Airproducts) was added. This was then thoroughly mixed by a mechanical stirrer for 5 seconds. The material was then molded and cured at 70° C. for 2.5 hours and post cured at 50° C. for another 3 hours.   
 
         [0177]    The foams in this example were made into dumbell shapes for tensile testing.  FIGS. 4 and 5  illustrate the difference in mechanical behaviour between the comparative materials indicating a favourable lowering in modulus for the triblock copolymer pre-soft-segments. 
       Example 7 
     Comparative Stability of Triblock Copolymer Soft Segment Versus Homopolymer Soft Segment 
       [0178]    Tensile test specimens were prepared in the same manner to the materials used in Example 4 and were subjected to accelerated aging in simulated gastric fluid (as per United States Pharmacopeia, “USP”). The materials produced with the pre-synthesised triblock copolymer soft segments resulted in substantially improved mechanical stability in gastric fluid as compared to the urethane/urea linked homopolymer equivalent as illustrated in  FIG. 6 . This facilitates the use of such materials for prolonged periods in digestive and more specifically gastric environments. 
       Example 8 
     Preparation of Water Blown Foams 
       [0179]    Several water blown polyurethane/urea foams were also produced with varying PO/EO/SiO polymer block ratios. The process for preparing the foam as described above was used. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Water blown formulations incorporating siloxane 
               
               
                 containing copolymer pre-soft-segments. 
               
             
          
           
               
                 Polymer block ratio 
                   
                   
                   
                   
               
               
                 (PO/EO/SiO) m:n:p 
                 DABCO 
                 BICAT 
                 DEOA 
                 H 2 O 
               
               
                   
               
               
                 41.5:8.3:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 40.2:7.8:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 37.5:7:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 33.5:5.7:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 29.6:4.4:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 21.6:1.8:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 19:1:0.5 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                 29.6:4.5:1.1 
                 0.114 
                 0.022 
                 0.22 
                 2.72 
               
               
                   
               
             
          
         
       
     
         [0180]    The results from the formulations described in Table 6 are shown in Table 7. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Results from mechanical testing of foams from Table 5 
               
             
          
           
               
                   
                 Polymer block ratio 
                 % 
                 Tensile 
               
               
                   
                 (PO/EO/SiO) m:n:p 
                 Elongation 
                 Strength (N) 
               
               
                   
                   
               
             
          
           
               
                   
                 41.5:8.3:0.5 
                 233 
                 0.46 
               
               
                   
                 40.2:7.8:0.5 
                 243 
                 0.31 
               
               
                   
                 37.5:7:0.5 
                 237 
                 0.3 
               
               
                   
                 33.5:5.7:0.5 
                 260 
                 0.23 
               
               
                   
                 29.6:4.4:0.5 
                 320 
                 0.23 
               
               
                   
                 21.6:1.8:0.5 
                 497 
                 0.23 
               
               
                   
                 19:1:0.5 
                 462 
                 0.22 
               
               
                   
                 29.6:4.5:1.1 
                 437 
                 0.29 
               
               
                   
                   
               
             
          
         
       
     
       Example 9 
     Use Example 
       [0181]    Devices for use in the gastrointestinal system have historically not been made from specifically designed materials. Off the shelf materials used for application in the corrosive environment of the stomach have limited biostability and generally lose their functionality after a short time. The foam of the invention can be used for production of a valve of the type described in our US2007-0198048A, the entire contents of which are incorporated herein by reference. The valve has an open position and a closed position. The valve will have a proximal end and a distal end. The valve material can open from the proximal direction when the action of swallowing (liquid or solid) stretches an oriface by between 100% and 3000% in circumference. The open orifice optionally closes non-elastically over a prolonged period of time, thus mimicking the body&#39;s natural response. The duration taken to close may be between 2 and 15 sec. The material can stretch to between 100%-300% from the distal direction when gas, liquid or solids exceeds a pre-determined force of between 25 cmH 2 O and 60 cmH 2 O. In some embodiments, the material absorbs less than 15% of its own mass of water at equilibrium. In some embodiments, the material loses (leaches) less than 3% of it&#39;s own mass at equilibrium in water or alcohol. In some embodiments, the material loses less than 10% of its tensile strength when immersed in a simulated gastric fluid at pH 1.2 for 30 days. In some embodiments, the valve material loses less than 25% of its % elongation when immersed in a simulated gastric fluid at pH 1.2 for 30 days. 
       Example 10 
     Valve Functional Testing 
       [0182]    The healthy lower esophageal sphincter (LES) remains closed until an individual induces relaxation of the muscle by swallowing and thus allowing food to pass in the antegrade direction. Additionally when an individual belches or vomits they generate enough pressure in the stomach in the retrograde direction to overcome the valve. An anti-reflux valve must enable this functionality when placed in the body, thus a simple functional test is carried out to asses performance. 
         [0183]    It has been reported that post fundoplication patients have yield pressures between 22-45 mmHg and that most of the patients with gastric yield pressure above 40 mmHg experienced problems belching. See  Yield pressure, anatomy of the cardia and gastro - oesophageal reflux . Ismail, J. Bancewicz, J. Barow British Journal of Surgery. Vol: 82, 1995, pages: 943-947. Thus, in order to facilitate belching but prevent reflux, an absolute upper GYP value of 40 mmHg (550 mmH 2 O) is reasonable. It was also reported that patients with visible esophagitis all have gastric yield pressure values under 15 mmHg, therefore, there is good reason to selectively target a minimum gastric yield pressure value that exceeds 15 mmHg. See Id. An appropriate minimum gastric yield pressure value would be 15 mmHg+25% margin of error thus resulting in a minimum effective valve yield pressure value of 18.75 mmHg or 255 mmH 2 O. 
         [0184]    The test apparatus consists of a 1 m high vertical tube as shown in  FIG. 7 , to which is connected a peristaltic pump and a fitting that is designed to house the valve to be tested. 
         [0185]    The valve to be tested is placed in a water bath at 37° C. for 30 minutes to allow its temperature to equilibrate. Once the temperature of the valve has equilibrated it is then installed into the housing such that the distal closed end of the valve faces the inside of the test apparatus. The pump is then switched on at a rate of 800 ml/min to begin filling the vertical tube. The rising column of water exerts a pressure that forces the valve shut initially. As the pressure in the column rises the valve reaches a point where it everts and allows the water to flow through. This point, known as the yield pressure, is then recorded and the test repeated four times. 
       Example 11 
     Rationale for Accelerated Aging of Material 
       [0186]    Clinical Condition being Simulated 
         [0187]    The lower oesophagus of a normal patient can be exposed to the acidic contents of the stomach periodically without any adverse side effects. However, patients with gastro esophageal reflux disease experience damage to the mucosa of the lower oesophagus due to increased exposure to the gastric contents. Exposure of the lower oesophagus to acidic gastric contents is routinely measured in the clinic using dedicated pH measurement equipment. A typical procedure involves measuring pH over a 24-hour period. The levels of acid exposure in pathological reflux disease patients is summarised in Table 8 from six clinical references. See DeMeester T R, Johnson L F, Joseph G J, et al.  Patterns of Gastroesophageal Reflux in Health and Disease Ann. Surg . October 1976 459-469; Pandolfino J E, Richter J E, Ours T, et al.  Ambulatory Esophageal pH Monitoring Using a Wireless System Am. J. Gastro  2003; 98:4; Mahmood Z, McMahon B P, Arfin Q, et al.  Results of endoscopic gastroplasty for gastroesophageal reflux disease: a one year prospective follow - up Gut  2003; 52:34-9; Park P O, Kjellin T, Appeyard M N, et al.  Results of endoscopic gastroplasty suturing for treatment of GERD: a multicentre trial Gastrointest endosc  2001; 53:AB115; Filipi C J, Lehman G A, Rothstein R I, et al.  Transoral flexible endoscopic suturing for treatment of GERD: a multicenter trial Gastrointest endosc  2001; 53 416-22; and Arts J, Slootmaekers S Sifrim D, et al.  Endoluminal gastroplication  ( Endocinch )  in GERD patient&#39;s refractory to PPI therapy Gastroenterology  2002; 122:A47. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Summary of acid exposure in patients with reflux disease 
               
             
          
           
               
                 Investigator 
                 Number of patients 
                 Details 
                 % 24 h &lt; pH 4 
               
               
                   
               
             
          
           
               
                 DeMeester 
                 54 
                 Combined refluxers 
                 13.5 
               
               
                 Pandolfino 
                 41 
                 Gerd 
                 6.5 
               
               
                 Mahmood 
                 21 
                 Gerd 
                 11.11 
               
               
                 Park 
                 142 
                 Gerd 
                 8.5 
               
               
                 Filipi 
                 64 
                 Gerd 
                 9.6 
               
               
                 Arts 
                 20 
                 Gerd 
                 17 
               
               
                 Average 
                   
                   
                 11.035 
               
               
                   
               
             
          
         
       
     
       Key Clinical Parameters 
       [0188]    Considering that the lower oesophagus is exposed to the acidic pH exposure time for an average of 11% of the measurement period, an accelerated aging methodology can easily be conceived. Constant exposure of a test material to the gastric contents (or USP Simulated Gastric Fluid—Reference USP Pharmacopeia) would represent an almost 10-fold increase in the rate of aging. Thus the time required to simulate one year of exposure of the lower oesophagus to the gastric contents is described by equation 1. 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       ( 
                       
                         11.035 
                         100 
                       
                       ) 
                     
                     × 
                     365 
                      
                     
                         
                     
                      
                     days 
                   
                   = 
                   
                     40.28 
                      
                     
                         
                     
                      
                     days 
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
       Clinical Rationale 
       [0189]    Immersion of test specimens in USP Simulated gastric fluid for 40.27 days at 37° C. will approximate one year&#39;s exposure of the lower oesophagus to acidic gastric contents in a GERD patient&#39;s scenario. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 9 
               
               
                   
                   
               
               
                   
                 Simulated Exposure 
                 Real Time 
               
               
                   
                   
               
             
             
               
                   
                 1 year 
                 40.28 days 
               
               
                   
                 2 years 
                 80.56 days 
               
               
                   
                 3 years 
                 120.84 days  
               
               
                   
                   
               
             
          
         
       
     
         [0190]    Results of accelerated stability of a valve prepared from a viscoelastic foam of the present invention are depicted in  FIGS. 8A and 8   b.    
         [0191]    The material used for may also be as described in our application entitled “A biomaterial” Ref: VYSE12 filed on the same date as this application. The entire contents of the VYSE12 application are herein incorporated by reference in its entirety. 
       Drug Delivery 
       [0192]    Drug delivery to the inner lumen of the alimentary canal is a technical challenge. The alimentary canal is a dynamic muscular structure that functions very efficiently to propel occluding items such as food through its length 
         [0193]    The most appropriate means of drug delivery through the mucosa of the alimentary tract is by topical administration (i.e.: applied directly to a part of the body). In order to achieve this, a delivery system must be designed to maintain uninterrupted intimate contact with the mucosa, for the required duration of treatment. In addition, the delivery system must be capable of carrying sufficient quantity of the therapeutic agent, and delivering this at a rate appropriate to the indication being treated. 
         [0194]    Some systems have been described to place a drug release patch in contact with the inner lumen of the gastro-intestinal tract but all of these have mechanical properties different to the oesophagus. This gives rise to periods of endothelial non-contact and thus interrupted drug release. 
         [0195]    In addition there may be cases where it is necessary to deliver a drug to a site close to a dysfunctional sphincter. In these cases drug delivery from the outer surface of an anti-reflux valve may be an appropriate solution. 
         [0196]    Systems have been described to place a drug release patch in contact with the inner lumen of the gastro-intestinal tract however in general, such systems give rise to periods of mucosal non-contact and thus interrupted drug release. 
         [0197]    We have developed novel biomaterials based upon segmented covalent copolymers of polydimethylsiloxane and polyether. Other variations of this material have been created that have polymer structures incorporating more hydrophobic or hydrophilic moeities. The microstructure of these materials is organised into hard and soft segments, which as illustrated in  FIG. 9 , phase separate into discrete ‘domains’ and self assemble during polymerisation. The size and proportion of hard and soft domains can be adjusted by varying the molecular weight of the chemical precursors. By tailoring the chemical nature of the domains in the material to be attractive to specific drug molecules (via hydrophobic interaction, hydrogen bonding and the like) drug can be spatially distributed and partitioned into these domains. Because the drug release is dependant on diffusion through both the hard and soft domains ie: the bulk of the material, an additional diffusion layer is unecessary. 
         [0198]    The microstructure gives rise to interesting mechanical properties that mimic the behaviour of some viscoelastic biological tissues. Upon application of mechanical stress the microstructure re-orientates resulting in alignment of the various segments as shown in  FIG. 10 . 
         [0199]    The hard segments of these materials can be controlled in many ways including the manipulation of their physical size, hydrophobicity/hydrophilicity, ionic characteristics, the extent to which they align and potentially their biostability/degradation. The material can also be formulated into either monolithic solids or soft porous foams with high surface areas (&gt;1.5 M 2 /g). 
         [0200]    The invention described here consists of a structure made from a material that mimics the mechanical properties of the gastrointestinal tract. The viscoelastic behaviour of this structure enables constant contact without the need for adhesive attachment. In addition the current invention is also a cellular foam, the structure and geometry of which can be altered to present a variety of surface areas available for direct contact as illustrated by  FIG. 11 . 
         [0201]    The rate of drug release can be controlled through variation of cellular structure and thus surface area is a novel means of achieving the optimum drug release kinetics. This approach has the additional benefit that diffusion control layers and the like are no longer necessary. The drug will be situated within the cell struts as illustrated in  FIG. 12  and thus the dimensions of these struts and the concentration of drug contained therein will influence the kinetic release properties. 
         [0202]    The use of a cellular foam material can also allow reloading of the drug delivery system while in-situ within the alimentary canal by injection of a drug solution directly into the foam. The foam cells can be between 0.5 and 1000 μm in diameter but ideally between 100 and 500 μm in diameter. The width of the struts (or walls) of the cells should be between 1 μm and 200 μm but more preferably between 1 μm and 10 μm. 
         [0203]    The density of the foam can be between 10 Kg/M 3  and 400 Kg/M 3  but more preferably between 50 Kg/M 3  and 150 Kg/M 3    
         [0204]    The compression and hysteresis behaviour of the foam material is shown in  FIG. 13  and is similar to that of human oesophageal tissue. 
         [0205]    The material used for drug delivery may also be as described in our application entitled “A biomaterial” Ref: VYSE12 filed on the same date as this application. The entire contents of the VYSE12 application are herein incorporated by reference in its entirety. 
         [0206]    The current invention can be used to deliver a variety of therapeutic agents including low molecular weight drugs such as H2 receptor antagonists, proton pump inhibitors or high molecular weight drugs such as proteins and peptides. In addition gene and cell based therapies can be delivered. Exemplary non-genetic therapeutic agents include anti-neoplastic/anti-proliferative/anti-mitotic agents such as paclitaxel, epothilone, cladribine, 5-fluorouracil, methotrexate, doxorubicin, daunorubicin, cyclosporine, cisplatin, vinblastine, vincristine, epothilones, endostatin, trapidil, halofuginone, and angiostatin; anti-cancer agents such as antisense inhibitors of c-myc oncogene; anti-microbial agents such as triclosan, cephalosporins, aminoglycosides, nitrofurantoin, silver ions, compounds, or salts; biofilm synthesis inhibitors such as non-steroidal anti-inflammatory agents and chelating agents such as ethylenediaminetetraacetic acid, O,O′-bis(2-aminoethyl)ethyleneglycol-N,N,N′,N′-tetraacetic acid and mixtures thereof; antibiotics such as gentamycin, rifampin, minocyclin, and ciprofolxacin; antibodies including chimeric antibodies and antibody fragments; anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; nitric oxide; nitric oxide (NO) donors such as lisidomine, molsidomine, L-arginine, NO-carbohydrate adducts, polymeric or oligomeric NO adducts; and any combinations and prodrugs of the above. 
         [0207]    Exemplary biomolecules include peptides, polypeptides and proteins; oligonucleotides; nucleic acids such as double or single stranded DNA (including naked and cDNA), RNA, antisense nucleic acids such as antisense DNA and RNA, small interfering RNA (siRNA), and ribozymes; genes; carbohydrates; angiogenic factors including growth factors; cell cycle inhibitors. Nucleic acids may be incorporated into delivery systems such as, for example, vectors (including viral vectors), plasmids or liposomes. 
         [0208]    Exemplary small molecules include hormones, nucleotides, amino acids, sugars, and lipids and compounds have a molecular weight of less than 100 kD. 
         [0209]    Exemplary cells include stem cells, progenitor cells, endothelial cells, adult cardiomyocytes, and smooth muscle cells. Cells can be of human origin (autologous or allogenic) or from an animal source (xenogenic), or genetically engineered. Non-limiting examples of cells include mesenchymal stem cells including mesenchymal stem cells with 5-aza, cord blood cells, endothelial progenitor cells, skeletal myoblasts or satellite cells, muscle derived cells, go cells, endothelial cells, genetically modified cells, tissue engineered grafts, embryonic stem cell clones, embryonic stem cells, fetal or neonatal cells, immunologically masked cells, and teratoma derived cells. 
         [0210]    The invention in one case provides a drug delivery system for application in the lower GI anatomy for treatment of Crohns Disease (CD). 
         [0211]    There is no known cure for CD. Primary treatment is aimed at relieving symptoms and reducing inflammation but the majority of people with CD require surgery at some point during their illness. Surgery is needed when the intestine is obstructed or when abscesses or fistulas do not heal. An operation to remove diseased sections of the intestine may relieve symptoms indefinitely but it does not cure the disease. CD tends to recur where the remaining intestine is rejoined (anastomosis) and a second operation is ultimately needed in nearly half of all patients. Most CD patients who have undergone surgery consider their quality of life to be better than it was before the operation. CD usually does not shorten a person&#39;s life, however, some people die of cancer of the digestive tract, which may develop in long-standing CD. 
         [0212]    The pathogenesis of Crohn&#39;s disease is incompletely understood. Current opinion implicates excessive activation of the gut mucosal immune system in genetically predisposed individuals, driven by the presence of the normal gut flora. Ample experimental evidence indicates that Crohn&#39;s disease is dependent on the gut flora, and that immune dysregulation has occurred. This view of Crohn&#39;s disease pathogenesis points to the two main pharmacological therapeutic strategies for treating CD, namely immunosuppression and antibiotics. 
         [0213]    The induction of mucosal healing is an important new concept in the management of Crohn&#39;s disease. Put simply, this concept states that treatments, surgical or medical, that result in the “healing” of the ulcerated and inflamed gut mucosa produce the best long-term outcomes. Therapies that allow ulceration to persist are associated with inferior long term results. 
         [0214]    Therefore, therapies that are focussed at controlling mucosal disease and result in healing are most likely to produce good long term responses. 
         [0215]    Antibiotics can be used to induce remission in mild-to-moderate CD. They are important for treating fistulas, bacterial overgrowth, abdominal abscesses and infections around the anus and genital areas. Randomized controlled clinical trial data support the use of nitroimidazole antibiotics such as metronidazole in the prevention of post-operative recurrence of active Crohn&#39;s disease in patients who have undergone segmental resection of the terminal ileum. Many experts also advocate the use of antibiotics in the treatment of active luminal Crohn&#39;s disease, although strong clinical trial data in support of this practice are lacking. Long term use of antibiotics such as metronidazole is significantly compromised by the occurrence of side effects, particularly dysguesia and peripheral neuropathy. The antibiotics used most commonly for inducing remission in CD are ciprofloxacin (Cipro) and metronidazole (Flagyl). 
         [0216]    Immunosuppression is an important pharmacological strategy in the long-term treatment of CD. Molecules such as the thiopurines azathioprine and 6-mercaptopurine, and the potent immunosuppressants cyclosporine and tacrolimus function by altering the activation of lymphocytes. Powerful immunosuppressant such as tacrolimus and cyclosporine are effective in Crohn&#39;s disease, but systemic side effects have tended to outweigh beneficial effects. Corticosteroids are highly beneficial in the short-term, but are not used long-term because of side effects. Anti-tumour necrosis factor biological therapeutics have also proven to be highly efficacious. All of these agents result in a decreased immune response at the site of the Crohns lesion. 
         [0217]    Therapy of Crohn&#39;s disease should be long-term. Many of the aforementioned molecules have dosage regimens lasting greater than 3 months. In addition they all have well characterised pharmocological and physicochemical properties as outlined in Table 10. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                   
                   
                   
                 Hydro- 
                 Mol- 
               
               
                   
                   
                   
                   
                   
                 phobicity/ 
                 ecular 
               
               
                   
                   
                 Oral 
                 IV 
                 MEC 
                 hydro- 
                 weight 
               
               
                 Molecule 
                 Class* 
                 dosage 
                 Dosage 
                 (ug/ml) 
                 philicty 
                 (g/mol) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 6-mercapto- 
                 IS 
                 100 
                 NA 
                 1 
                   
                 152 
               
               
                 purine 
                   
                 mg/day 
                   
                 mcg/ml 
                   
                   
               
               
                 Azathioprine 
                 IS 
                 150 
                 NA 
                 1 
                   
                 277 
               
               
                   
                   
                 mg/day 
                   
                 mcg/ml 
                   
                   
               
               
                 Ciprofloxacin 
                 AB 
                 1 g/day 
                 1 g/day 
                 0.2 
                   
                 331 
               
               
                   
                   
                   
                   
                 mcg/ml 
                   
                   
               
               
                 Cyclosporine 
                 IS 
                 500 
                 300 
                 0.1-0.4 
                 Very 
                 1202 
               
               
                   
                   
                 mg/day 
                 mg/day 
                 mcg/ml 
                 hydro- 
                   
               
               
                   
                   
                   
                   
                   
                 phobic 
                   
               
               
                 Metronidazole 
                 AB 
                 1 g/day 
                 1 g/day 
                 8 
                   
                 171 
               
               
                   
                   
                   
                   
                 mcg/ml 
                   
                   
               
               
                 Tacrolimus 
                 IS 
                 15 
                 15 
                 0.01- 
                   
                 804 
               
               
                   
                   
                 mg/day 
                 mg/day 
                 0.02 
                   
                   
               
               
                   
                   
                   
                   
                 mcg/ml 
               
               
                   
               
               
                 *IS = Immunosuppresant, AB = Antibiotic 
               
             
          
         
       
     
         [0218]    In order to investigate the extent of drug loading for different drug types, material formulations of varying hydrophilicity and hydrophobicity were created. The hydrophilicity was influenced by the proportion of poly(ethylene oxide) to poly(propylene oxide) to siloxane as shown by Table 11. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 11 
               
             
             
               
                   
               
               
                 Proportions of polymer chains used in the material formulations 
               
             
          
           
               
                   
                 PPO 
                 PEO 
                 SiO 
               
               
                   
                   
               
             
          
           
               
                   
                 DD 170608 
                 0 
                 0 
                 48.63 
               
               
                   
                 DD 180608B 
                 17.12 
                 3.44 
                 29.182 
               
               
                   
                 DD 190608A 
                 42.8 
                 8.6 
                 0.01008 
               
               
                   
                   
               
             
          
         
       
     
       Methodologies—Drug Loading 
       [0219]    The drug films of Table 11 were made with the material described in Example 6 above. Drug loading of polymer films was achieved by swelling the samples in an appropriate solvent. Such solvents were selected on the basis of their compatibility with the test drugs intended for use. The extent of solvent swelling and thus drug loading was also dependant on the properties of the material formulations as illustrated by  FIG. 14 . 
         [0220]    Theoretical drug loadings for the two compounds used are given in Table 12 below. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 12 
               
             
             
               
                   
               
               
                 Theoretical loading values for the three 
               
               
                 material formulations used in this study. 
               
             
          
           
               
                   
                   
                 Theoretical 
                 Theoretical 
               
               
                   
                 Batch 
                 metronidazole 
                 cyclosporine 
               
               
                 Material 
                 number 
                 loading (mg/cm2) 
                 loading (mg/cm2) 
               
               
                   
               
             
          
           
               
                 A (n = 3) 
                 DD170608 
                 9.76 mg 
                 19.4 
               
               
                 B (n = 3) 
                 DD180608B 
                 19.9 mg 
                 30 
               
               
                 C (n = 3) 
                 DD190608A 
                 32.0 mg 
                 55 
               
               
                   
               
             
          
         
       
     
       Methodology—Drug Release 
       [0221]    In vitro release studies were preformed on each of the three film formulations, for each drug, in triplicate. Each film was placed into a 100 mL volumetric flask containing 100 mL PBS (pH 7.4) as the release medium. The films were incubated at 37° C. in a water bath at a shaker speed of 300 rpm Water Bath. Samples of the release medium (2 mL) were taken at several time intervals over the first day and subsequently at daily or every alternate day until dissolution appeared complete. Samples were replaced with fresh 2 mL aliquot of PBS (pH 7.4) at each sampling point. Samples were analysed for metronidazole content using a Biochrom Libra S22 UV/VIS spectrophotometer at a wavelength of 277 nm using the calibration equations prepared below. Cyclosporin containing samples were assayed using HPLC analysis. 
         [0222]    The drug release profiles were analysed and compared for each drug from the 3 different formulations. Release rates were calculated to determine the feasibility of achieving and maintaining minimum effective concentrations (MEC) of each drug over a 2-4 week period. 
       Results 
       [0223]    Metronidazole Release from Films 
         [0224]    The release profiles of metronidazole are expressed as mean and standard deviation are shown in  FIGS. 15 and 16  below. 
         [0225]    The release profiles of metronidazole, show an initial burst release during day one followed by a slower release phase over the next 13 days of testing. The magnitude of the initial burst was dependant on the initial metronidazole loading, increasing with an increase in theoretical drug loading. The daily amount of active released from the films decreased with time elapsed gradually reaching a plateau by day=7 for films A and C particularly. The total amount of drug released over the study time was highest from material C followed by material B and then material A and was in proportion with theoretical drug loading of the films. 
         [0226]    As a percentage of the theoretical loading of metronidazole in the films, 3.8% was released over the 13 day release study from material A, 9.7% metronidazole was released from material B over 14 days and 6.3% metronidazole was release from material C after 13 days dissolution. 
         [0000]    Cyclosporin Release from Films 
         [0227]    Cyclosporin release was studied as per the method described and samples were removed after 0.5, 1, 2, 3, 4, 5, 6, 24 and 48 hours then twice weekly until day 16. A last sample was taken at day 30. Analysis of the samples did not show any drug peak in the first 5 days when analysed using HPLC. 
         [0228]    A cyclosporin peak in the HPLC chromatograms was observed for all dissolution samples taken from Day 7 to day 30. The release observed for all three films showed a maximum release on day 16 at 0.75-0.98 mcg/ml. Analysis of samples at day 30 however showed a lower concentration of cyclosporin at 0.40-0.67 μg/ml. The release profile for Cyclosporine is shown in  FIG. 17 . 
         [0229]    The results from this study show that metronidazole release from comparable films is faster than release of cyclosporin. This is related to the different solubility characteristics of the two drugs, metronidazole having a higher water solubility than cyclosporine. The release of both drugs was controlled to a certain extent from all film prototypes studied which is encouraging for future development of sustained release films. A trend of increasing drug release with increasing drug loading of films was observed for metronidazole. For cyclosporine, no drug release was detected for the first 5 days. After day 7, drug release was shown by a detectable peak, however drug level was very low. Drug release was similar for all 3 film formulations irrespective of drug loading. For both films only a small proportion of drug was released over the measured timescale, indicating that both drug systems have the potential for prolonged release. 
         [0230]    The thermoplastic material of the invention may be applied to a medical device as a coating or additionally may be extruded into a specific shape. A solution of the thermoplastic polyurethane may be applied to a stent or other device, which is held on a PTFE mandrel. A continuous coating will be formed through the evaporation of the carrier solvent. This will in turn provide a protective coating to a stent of other medical device. 
         [0231]    By evaporation of the solvent used in the production of the thermoplastic polyurethane a solid polymer suitable for extrusion can be formed. For example a polymer produced in the examples may be extruded at 190° C. with 5 Kg of force resulting in a Melt Flow Index (ISO 1133) of 0.475 g/10 mins. Such an extrusion could be used to build a catheter or other tubular device. 
         [0232]    While we have described a number of embodiments of this invention, it is apparent that our basic examples may be altered to provide other embodiments that utilize the compounds and methods of this invention. Therefore, it will be appreciated that the scope of this invention is to be defined by the appended claims rather than by the specific embodiments that have been represented by way of example. 
         [0233]    Various features of the invention are described in detail and illustrated herein. Appropriate features described with reference to one embodiment may be utilised in addition to and/or as a substitute for features described in other embodiments. 
         [0234]    The invention is not limited to the embodiments hereinbefore described which may be varied in detail. 
       REFERENCES 
       [0000]    
       
         1. M F Francis, L Lavoie, F M Winnik, J C Leroux, Solubilization of cyclosporin A in dextran-g-polyethyleneglycolalkyl ether polymeric micelles.  European Journal of Pharmaceutics and Biopharmaceutics,  56, (2003); 337-346.