Abstract:
Biomedical and tissue engineering devices, such as surgical sutures and microporous scaffolds, respectively, which undergo swelling and increase in dimensions when placed in aqueous environments such as living tissues, are produced by the melt-spinning or electrostatic spinning into strong monofilament and multifilament yarns or microfibrous fabrics, respectively. Such devices are formed from especially high molecular weight crystalline polyether-esters having a minimum inherent viscosity of 0.8 dL/g and heat of fusion of at least 5 J/g, wherein the polyether-esters are made by grafting to a polyester component a polyether glycol component having a minimum molecular weight of about 1 kDa with at least one cyclic monomer.

Description:
The present application is a continuation in part of patent application U.S. Ser. No. 11/453,207 filed on Jun. 14, 2006, which claims the benefits of prior provisional application U.S. Ser. No. 60/690,751 filed Jun. 15, 2005. 
    
    
     FIELD OF THE INVENTION 
     This invention is directed toward a swellable, absorbable polyether-ester with a sufficiently high molecular weight and degree of crystallinity to allow their conversion by melt-spinning or electrostatic spinning to produce strong monofilament yarns, multifilament yarns or non-woven microfibrous fabrics, respectively, for use in biomedical, pharmaceutical, and tissue engineering application devices. Such devices possess sufficiently low modulus and, in effect, low compliance to be biomechanically compatible when interfacing with living tissues. The composition of the constituent polymeric chains of these materials are tailored to allow the corresponding devices to undergo an increase in their compliance and dimension by swelling when placed in an aqueous environment, as in the case of living tissues. 
     BACKGROUND OF THE INVENTION 
     There have been described in prior disclosure U.S. patent application Ser. No. 11/175,636, as well as the present parent application, (1) absorbable amphiphilic block copolymeric compositions of polyether-esters having an inherent viscosity of at least 0.5 dL/g and a heat of fusion of at least 10 J/g, which can undergo swelling in an aqueous environment as a in living tissues due to water up-take of at least 10 percent of their original mass; and (2) that such amphiphilic block copolymeric compositions can be converted to complaint monofilament and multifilament braids. However, it has been discovered during the course of the study associated with the present invention, that in order to produce commercially useful and clinically competitive biomedical devices, such as surgical sutures, and tissue engineering scaffolds comprising swellable, absorbable, high strength, melt-spun monofilament and multifilament yarns or high strength electrostatically spun microfibrous, non-woven fabrics, the constituent amphiphilic polyether-esters must meet more stringent requirements than those disclosed earlier in terms of molecular weight and degree of crystallinity, which can be expressed in terms of inherent viscosity and heat of fusion, respectively. To prepare polyether-esters of sufficiently high molecular weight and degree of crystallinity to produce the required high strength melt-spun monofilament and multifilament yarns or electrostatically spun microfibers, while maintaining a sufficient degree of amphiphilicity to achieve clinically practical levels of swellability in the biological environment, the need to use polyether glycol intermediates having a minimum molecular weight of 11 kDa, was surprisingly uncovered during the course of the study associated with the present invention. This, in turn, demonstrates the novelty of the present invention when contrasted with a distantly relevant prior art, particularly US Publication No. 2007/0014848, where polyether intermediates, having a maximum molecular weight of 10 kDa, have been used to produce relatively lower molecular weight and in most cases, practically amorphous polyether-esters unsuitable for conversion into the yarns and microfibers. 
     SUMMARY OF THE INVENTION 
     Generally, the present invention is directed to a swellable, absorbable, fiber- or microfiber-forming, high molecular weight, crystalline polyether-ester having a (a) polyether chain component with a molecular weight of more than about 11 kDa; (b) an inherent viscosity of at least 0.8 dL/g in chloroform or hexafluoroisopropyl alcohol; and (c) heat of fusion exceeding 5 J/g, wherein the fibers or microfibers thereof undergo at least 0.5% increase in their cross-sectional area when placed in an aqueous environment as in living, soft tissues for less than three (3) hours, wherein the polyether-ester comprises a polyether glycol grafted with at least one cyclic monomer selected from the group consisting of l-lactide, ε-caprolactone, glycolide, p-dioxanone, trimethylene carbonate, and a morpholinedione, and wherein the polyether chain component of the polyether-ester is a polyethylene oxide. Alternatively, the polyether chain component of the polyether-ester is a block copolymer of polyethylene oxide and polypropylene oxide or is a random copolymer of ethylene oxide and propylene oxide. 
     Another aspect of this invention deals with a swellable, absorbable, fiber- or microfiber-forming, high molecular weight, crystalline polyether-ester having a (a) polyether chain component with a molecular weight of more than about 11 kDa; (b) an inherent viscosity of at least 0.8 dL/g in chloroform or hexafluoroisopropyl alcohol; and (c) heat of fusion exceeding 5 J/g, wherein the fibers or microfibers thereof undergo at least 0.5% increase in their cross-sectional area when placed in an aqueous environment as in living, soft tissues for less than three (3) hours, wherein the polyether-ester comprises a polyether glycol grafted with at least one cyclic monomer selected from the group consisting of l-lactide, ε-caprolactone, glycolide, p-dioxanone, trimethylene carbonate, and a morpholinedione, and wherein the polyether-ester is in the form of (1) a monofilament yarn made by melt-spinning and further converted to a surgical suture; (2) a multifilament yarn made by melt-spinning and further processed into a braided surgical suture; (3) a multifilament yarn and further processed into a compressible, microporous felt for use as a scaffold for tissue engineering; or (4) a non-woven, microporous, microfibrous fabric made by electrostatic spinning of a solution of said polyether-ester in an organic solvent or a mixture of solvents. It is also the objective of this invention that the monofilament suture matrix comprises at least one bioactive agent selected from the group of agents known for their antimicrobial, antineoplastic or tissue growth promoting activities, and when said suture is implanted in living tissues, exhibits a ratio of the percent breaking strength retention/absorption (measured in terms of mass loss, reduction in volume or reduction in cross-sectional area) at a given time period that is at least 5% lower than those established for the parent polyester of the polyester chain component of the respective polyether-ester. 
     A specific aspect of this invention deals with such a polyether-ester is in the form a monofilament yarn made by melt-spinning and further converted to a surgical suture that displays a breaking strength of more than 30 Kpsi and a modulus of less than 300 Kpsi, and more specifically, the modulus of the surgical suture decreases by at least 5% after less than 3 hours following its placement in an aqueous environment as in living tissues. 
     Preferably, the monofilament suture further comprises an absorbable coating, which includes at least one bioactive agent selected from the group of agents known for their antimicrobial, antineoplastic, or tissue growth promoting activities. 
     In another embodiment the polyether-ester is in the form of a multifilament yarn made by melt-spinning and further processed into a braided surgical suture that comprises an absorbable coating, which contains at least one bioactive agent selected from the group of agents known for their antimicrobial, antineoplastic, or tissue growth promoting activities. 
     In a clinically important aspect of this invention the polyether-ester is in the form of a multifilament yarn and further processed into a compressible, microporous felt for use as a scaffold for tissue engineering and the felt has an absorbable coating, which contains at least one bioactive agent selected from the group of agents known for their antimicrobial, antineoplastic, or tissue growth promoting activities. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     This invention generally is directed toward especially tailored, absorbable polyether-esters, which exhibit sufficiently high molecular weight and melt-viscosity to allow their eventual conversion to oriented, dimensionally stable monofilament and multifilament yarns suitable for use in constructing high strength surgical sutures or microporous felt for tissue engineering applications. This invention also discloses the general use of the especially tailored, high molecular weight crystalline polyether-esters, which can exhibit high viscosity solutions with low solute content, optimal for the electrospinning of high strength microfibrous constituents of microporous fabrics that can, in turn, be useful clinically as covers for wounds, ulcers, and scaffolds for tissue engineering as well as filters for cell fractionation. To meet the stringent requirements and for producing the aforementioned swellable constructs comprising high strength monofilament and multifilament yarns or electrospun microfibrous yarns, the present invention addresses equally stringent physicochemical requirements for the polyether-esters suitable for use in the eventual production of the swellable devices disclosed herein. These requirements include, but are not limited to, (1) using a polyether glycol having a molecular weight exceeding 11 kDa for grafting with at least one cyclic monomer to produce ABA-type block copolymer exhibiting a high molecular weight associated with an inherent viscosity of at least 0.8 dL/g for a dilute solution in chloroform or hexafluoroisopropyl alcohol (HFIP) of about 0.1 percent (weight/volume); (2) adjusting the polyether-to-polyester weight ratio in the chain so as to guarantee attaining the sought molecular weight without compromising the amphiphilicity level needed to achieve a minimum of 0.5 percent increase in fiber or microfiber cross-sectional area when in the presence of an aqueous environment as in living tissue for less than three hours; (3) selecting one or more monomer for end-grafting onto the polyether glycol as to yield crystalline products, which can be converted to devices that are dimensionally stable during critical processing steps and upon storage; (4) selecting combinations of a polyether-type, as in polyethylene glycol, and block or random copolymers of ethylene and propylene oxides as well as cyclic monomers known to provide a range of hydrolytic stability as glycolide (or a morpholine dione), lactide (or ε-caprolactone and trimethylene carbonate) to yield polyether-esters with unique absorption-strength retention profiles wherein the rates of breaking strength decay relative to the rates of absorption/mass loss are then those established for the traditional polyesters that are not part of a polyether-ester block copolymeric structure; (5) selecting the ring-opening polymerization charge and reaction conditions to insure the formation of the desired copolymeric chain structure and distribution of constituent repeat units, which, in turn, control the degree of crystallinity, as well as the thermal properties and solubility, which are pertinent to applied melt processing and electrospinning protocols; and (6) selecting the proper polyether/polyester ratios to allow optimal incorporation of a specific bioactive agent into the matrix of the fibrous or microfibrous constituents of the device. 
     Further illustrations of the present invention are provided by the following examples: 
     Example 1 
     Preparation and Characterization of Crystalline Amphiphilic Triblock Block Copolymer Having a Central Polyethylene Oxide and Polyester Terminal Blocks (P-I Series) 
     General Method 
     Predried crystalline, high molecular weight PEG is mixed, under nitrogen in a stainless steel reactor equipped for mechanical stirring, with the desired amount(s) of cyclic monomer(s) in the presence of stannous octanoate as a catalyst. The mixture is then heated to achieve complete dissolution of all reactants. The mixing is continued while heating to a polymerization temperature of 160 to 180° C. depending on the type and concentration of cyclic monomer(s). The reaction is maintained at that temperature while stirring until the product becomes too viscous to stir and essentially complete monomer conversion is achieved (8-10 hours depending on the type and concentration of cyclic monomer(s)). At this stage, polymerization is discontinued, the product is cooled, isolated, ground, dried, and traces of residual monomer are removed by distillation under reduced pressure using a temperature that is below the copolymer melting temperature (T m ), but not exceeding 110° C., or by precipitation. 
     The resulting copolymer is characterized for (a) molecular weight in terms of inherent viscosity (I.V.) and M n /M w  by GPC if the polymer is soluble in CH 2 Cl 2 ; (b) T m  and heat of fusion (ΔH f ) using differential scanning calorimetry; (c) crystallinity using wide-angle X-ray diffraction. 
     Examples 2 to 10 
     Synthesis and Characterization of Specific Examples of Type P-I Block Copolymers (P-I-A to P-I-I) 
     Copolymers P-I-A to P-I-I are prepared and characterized following the general methods described in Example 1. The polymerization charge and properties of resulting polymers are summarized in Table I. 
     Example 11 
     Preparation and Characterization of Crystalline, Amphiphilic, Triblock Block Copolymer Having a Central Polyether Block Composed of a Block or Random Copolymer of Ethylene and Propylene Oxides and Polyester Terminal Blocks (P-II Series) 
     General Method 
     Predried, high molecular weight block or random copolymer of ethylene and propylene oxides is mixed under nitrogen in a stainless steel reactor equipped for mechanical stirring, with the desired amount(s) of cyclic monomer(s) in the presence of stannous octanoate as a catalyst. The mixture is then heated to achieve complete dissolution of all reactants. The mixing is continued while heating to a polymerization temperature of 140 to 180° C. depending on the type and concentration of cyclic monomer(s). The reaction is maintained at that temperature while stirring until the product becomes too viscous to stir and essentially complete monomer conversion is achieved (8-60 hours depending on the type and concentration of cyclic monomer(s)). At this stage, polymerization is discontinued, the product is cooled, isolated, ground, dried, and traces of residual monomer are removed by distillation under reduced pressure using a temperature that is below the copolymer melting temperature (T m ), but not exceeding 110° C., or by precipitation. 
     The resulting copolymer is characterized for (a) molecular weight in terms of inherent viscosity (I.V.) and M n /M w  by GPC if the polymer is soluble in CH 2 Cl 2 ; (b) T m  and heat of fusion (ΔH f ) using differential scanning calorimetry; (c) crystallinity using wide-angle X-ray diffraction. 
     Examples 12 to 15 
     Synthesis and Characterization of Specific Examples of Type P-II Block Copolymers (P-II-A to P-II-D) 
     Copolymers P-II-A to P-II-D were prepared and characterized following the general methods described in Example 11. The polymerization charge and properties of resulting polymers are summarized in Table II. 
     Example 16 
     Preparation and Characterization of Crystalline, Amphiphilic Block Copolymer of Polyethylene Glycol (PEG) and Polyester Interlinked with Low T g  Polymer Segments (P-III Series): 
     General Method 
     The general polymerization methods and polymer isolation, purification, and characterization of P-III series are implemented using analogous experimental protocols as those described in Example 1 for the P-I series with the exception of the following: 
     The PEG is first end-grafted with trimethylene carbonate (TMC) or a TMC or ε-caprolactone (CL) rich comonomer mixture at 150 to 180° C. (depending on the type and concentration of cyclic monomer(s)) until essentially complete monomer conversion is achieved yielding a PEG-Low T g  Segment copolymer. At this point, the temperature is lowered to 140° C. and the monomeric precursor(s) of the crystalline hydrophobic component(s) are added and thoroughly mixed with the PEG-Low T g  Segment copolymer. The reaction temperature is then raised to 140° C. to 160° C. depending on the type and concentration of cyclic monomer(s), and polymerization is continued. 
     Examples 17 to 23 
     Synthesis and characterization of specific examples of type P-III block Copolymers (P-III-A to P-III-G) 
     Copolymers P-III-A to P-III-G were prepared and characterized following the general methods described in Example 16. Polymerization charge and properties of resulting polymers are summarized in Table III. 
     Example 24 
     Melt-Spinning of Typical Block Copolymers into Typical Monofilaments 
     The melt spinning of four typical block copolymers are accomplished using a ¾″ extruder at the temperature noted in Table IV. The extrudates are oriented in two stages using the draw ratio/temperature noted in Table IV. 
     Example 25 
     Properties of Typical Oriented Monofilaments as Swellable Sutures 
     The initial tensile properties and breaking strength retention (BSR) properties of the monofilament sutures are determined using a MiniBionix MTS Universal Tester, Model 858. The simulated bioswelling properties are evaluated using a phosphate buffer at 37° C. and pH 7.4. The in vitro BSR properties are determined on sutures incubated in a phosphate buffer at 37° C. and pH 7.4. The in vivo BSR properties are determined on sutures after subcutaneous implantation in Sprague-Dawley rats. The accelerated in vitro mass loss properties are determined on sutures incubated in a phosphate buffer at 37° C. and pH 12.0. Properties of typical oriented monofilaments as swellable sutures are shown in Table V. 
     Example 26 
     Melt-Spinning of Typical Block Copolymers into Typical Multifilaments and Preparation of Braided Sutures Thereof 
     The multifilament melt spinning of two typical block copolymers are accomplished using a multi-hold die, under slightly higher thermal conditions as compared to those used in the production of the monofilaments in Example 24. Depending on the copolymer type and required yarn denier, the extruded multifilament yarns are oriented in two stages at a temperature range of either 50 to 70° C. or 65° C. to 85° C. Block copolymers P-II-A and P-II-D are converted to braided multifilaments, and tested for their tensile properties using a MiniBionix MTS Universal Tester, Model 858. Braided multifilaments of block copolymers P-I-A and P-II-D, with diameters of 0.45 and 0.32 mm respectively, exhibit tensile strengths of 40.0 and 52.7 Kpsi and elongations of 48% and 24% respectively. 
     Example 27 
     Preparation and Electrospinning of Typical Block Copolymers 
     Electrospinning is accomplished on an electrospinning unit constructed in-house from the polymers listed in Table I below. Solutions were prepared by dissolving 10-30 w/v % polymer, depending on the polymer molecular weight and desired fiber diameter, in a mixture of 1:1 dichloromethane:chloroform. Electrospinning is conducted using the following conditions: +10-25 kV charge at needle tip, −15-0 kV charge at collection drum, 16-22 g blunt end needle, 0.02-0.15 mL/min flow rate, and 5-15″ tip-to-collector distance. 
     Example 28 
     Properties of Typical Non-woven Microfibrous Fabrics Prepared by Electrospinning 
     Electrospun fabrics prepared as described above were analyzed and found to have the following properties (see Table VI). 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Synthesis and Properties of Copolymers P-I-A to P-I-I 
               
             
          
           
               
                   
                 Composition of Charge 
                   
               
             
          
           
               
                 Poly- 
                   
                 PEG/ 
                 Monomer 
                   
                   
                   
                   
               
               
                 mer 
                 PEG 
                 Poly- 
                 Types &amp; 
                 Cat- 
                 GPC c  Data 
                   
                 DSC Data 
               
             
          
           
               
                 Num- 
                 M n , 
                 ester, 
                 Molar 
                 alyst 
                 Mn, 
                 Mw, 
                   
                 Tm, 
                 ΔH f , 
               
               
                 ber 
                 kD 
                 (wt) 
                 Ratios a   
                 M/C b   
                 kDa 
                 kDa 
                 IV d   
                 ° C. 
                 J/g 
               
               
                   
               
             
          
           
               
                 P-I-A 
                 20 
                  6/94 
                 92/8 
                 16000 
                 e 
                 e 
                 1.50 
                 223 
                 105 
               
               
                   
                   
                   
                 G/TMC 
                   
                   
                   
                   
                   
                   
               
               
                 P-I-B 
                 35 
                  6/94 
                 92/8 
                 14000 
                 e 
                 e 
                 1.39 
                 47, 
                 12, 
               
               
                   
                   
                   
                 G/TMC 
                   
                   
                   
                   
                 224 
                 78 
               
               
                 P-I-C 
                 35 
                 10/90 
                 70/30 
                 8000 
                 e 
                 e 
                 1.79 
                 50, 
                 12, 
               
               
                   
                   
                   
                 G/CL 
                   
                   
                   
                   
                 127, 
                 6, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                 223 
                 78 
               
               
                 P-I-D 
                 20 
                 10/90 
                 70/30 
                 16000 
                 e 
                 e 
                 1.79 
                 46, 
                 2, 
               
               
                   
                   
                   
                 G/CL 
                   
                   
                   
                   
                 218 
                 65 
               
               
                 P-I-E 
                 35 
                 15/85 
                 70/30 
                 10000 
                 e 
                 e 
                 1.51 
                 55, 
                 11, 
               
               
                   
                   
                   
                 G/CL 
                   
                   
                   
                   
                 128, 
                 15, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                 211 
                 31 
               
               
                 P-I-F 
                 11 
                  7/93 
                 95/5 
                 3000 
                 126 
                 245 
                 (1.72) 
                 51, 
                 6, 
               
               
                   
                   
                   
                 LL/TMC 
                   
                   
                   
                   
                 154 
                 15 
               
               
                 P-I-G 
                 14 
                  9/91 
                 95/5 
                 3000 
                  51 
                 157 
                 (0.68) 
                 149 
                 35 
               
               
                   
                   
                   
                 LL/TMC 
                   
                   
                   
                   
                   
                   
               
               
                 P-I-H 
                 20 
                 13/87 
                 95/5 
                 3000 
                  86 
                 203 
                 (1.45) 
                 43, 
                 10, 
               
               
                   
                   
                   
                 LL/TMC 
                   
                   
                   
                   
                 157 
                 35 
               
               
                 P-I-I 
                 11 
                  9/91 
                 95/5 
                 3000 
                 109 
                 257 
                 (1.51) 
                 47, 
                 3, 
               
               
                   
                   
                   
                 LL/TMC 
                   
                   
                   
                   
                 160 
                 26 
               
               
                   
               
               
                   a G = Glycolide; TMC = trimethylene carbonate; CL = ε-caprolactone; LL = l-lactide. 
               
               
                   b Molar ratio of monomer to stannous octanoate. 
               
               
                   c Gel permeation chromatography in CH 2 Cl 2 . 
               
               
                   d Inherent viscosity in HFIP (in CHCl 3 ). 
               
               
                   e Insoluble in CH 2 Cl 2 . 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 Synthesis and Properties of Copolymers P-II-A to P-II-D 
               
             
          
           
               
                   
                 Composition of Charge 
                   
               
             
          
           
               
                   
                   
                   
                 Monomer 
                   
                   
                   
                   
               
               
                   
                 Polyether 
                 Polyether/ 
                 Types &amp; 
                   
                 GPC c  Data 
                   
                 DSC Data 
               
             
          
           
               
                 Polymer 
                 Type a / 
                 Polyester, 
                 Molar 
                 Catalyst 
                 Mn, 
                 Mw, 
                   
                 Tm, 
                 ΔH f , 
               
               
                 Number 
                 M n , kD 
                 (wt) 
                 Ratios a   
                 M/C b   
                 kDa 
                 kDa 
                 IV d   
                 ° C. 
                 J/g 
               
               
                   
               
               
                 P-II-A 
                 ran/12 
                  5/95 
                 70/30 
                 8000 
                 e 
                 e 
                 1.95 
                 124 
                 26 
               
               
                   
                   
                   
                 G/CL 
                   
                   
                   
                   
                   
                   
               
               
                 P-II-B 
                 ran/12 
                 10/90 
                 70/30 
                 8000 
                 e 
                 e 
                 1.26 
                 125, 
                 7, 
               
               
                   
                   
                   
                 G/CL 
                   
                   
                   
                   
                 217 
                 37 
               
               
                 P-II-C 
                 blk/15 
                 10/90 
                 70/30 
                 8000 
                 e 
                 e 
                 1.53 
                 130, 
                 6, 
               
               
                   
                   
                   
                 G/CL 
                   
                   
                   
                   
                 220 
                 35 
               
               
                 P-II-D 
                 ran/12 
                  5/95 
                 96/4 
                 5000 
                 107 
                 270 
                 (1.78) 
                 181 
                 81 
               
               
                   
                   
                   
                 LL/TMC 
               
               
                   
               
               
                   a ran = random: blk = block 
               
               
                   b G = Glycolide; TMC = trimethylene carbonate; CL = ε-caprolactone; LL = l-lactide. 
               
               
                   c Molar ratio of monomer to stannous octanoate. 
               
               
                   d Gel permeation chromatography in CH 2 Cl 2 . 
               
               
                   e Inherent viscosity in HFIP (in CHCl 3 ). 
               
               
                   f Insoluble in CH 2 Cl 2 . 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE III 
               
             
             
               
                   
               
               
                 Synthesis and Properties of Copolymers P-III-A to P-III-G 
               
             
          
           
               
                   
                 Composition of Charge 
                   
               
             
          
           
               
                   
                   
                   
                   
                 Polyester 
                   
                   
                   
                   
               
               
                 Polymer 
                 PEG 
                 PEG/Low Tg 
                 Low Tg Segment 
                 Monomer 
                   
                 GPC c  Data 
                   
                 DSC Data 
               
             
          
           
               
                 Number 
                 M n , 
                 Segment/ 
                 Monomer Types 
                 Types &amp; molar 
                 Catalyst 
                 Mn, 
                 Mw, 
                   
                 Tm, 
                 ΔH f , 
               
               
                 P-III- 
                 kD 
                 Polyester, (wt) 
                 &amp; Molar Ratios a   
                 ratios a   
                 M/C b   
                 kDa 
                 kDa 
                 IV d   
                 ° C. 
                 J/g 
               
               
                   
               
               
                 A 
                 20 
                 9/16/75 
                 85/15 CL/LL 
                 96/4 LL/CL 
                 3k 
                 98 
                 203 
                 1.49 
                 43, 
                 6, 56 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 174 
                   
               
               
                 B 
                 11 
                 10/43/47 
                 60/24/16 
                 81/19 LL/G 
                 6k 
                 65 
                 130 
                 1.29 
                 104 
                 6 
               
               
                   
                   
                   
                 CL/TMC/G 
                   
                   
                   
                   
                   
                   
                   
               
               
                 C 
                 35 
                 20/10/70 
                 97/3 TMC/CL 
                 96/4 LL/CL 
                 3k 
                 95 
                 180 
                 1.28 
                 42, 
                 9, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 158 
                 24 
               
               
                 D 
                 20 
                 23/2/75 
                 TMC 
                 96/4 LL/CL 
                 3k 
                 69 
                 150 
                 0.97 
                 41, 
                 11, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 156 
                 25 
               
               
                 E 
                 35 
                 25/10/65 
                 97/3 TMC/CL 
                 96/4 LL/CL 
                 3k 
                 78 
                 163 
                 1.13 
                 45, 
                 21, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 150 
                 20 
               
               
                 F 
                 35 
                 30/5/65 
                 97/3 TMC/CL 
                 96/4 LL/CL 
                 3k 
                 75 
                 155 
                 0.98 
                 51, 
                 22, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 141 
                 19 
               
               
                 G 
                 35 
                 35/5/60 
                 97/3 TMC/CL 
                 96/4 LL/CL 
                 2k 
                 74 
                 150 
                 1.08 
                 53, 
                 30, 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 145 
                 23 
               
               
                   
               
               
                   a G = Glycolide; TMC = trimethylene carbonate; CL = ε-caprolactone; LL = l-lactide. 
               
               
                   b Molar ratio of monomer to stannous octanoate. 
               
               
                   c Gel permeation chromatography in CH 2 Cl 2 . 
               
               
                   d Inherent viscosity in CHCl 3   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE IV 
               
             
             
               
                   
               
               
                 Extrusion and Processing Conditions of Typical Monofilaments 
               
             
          
           
               
                   
                   
                 Orientation 
               
               
                   
                 Temperature Profile During extrusion, 
                 Scheme Draw 
               
               
                 Polymer 
                 ° C. @ 
                 Ratio/Temp, 
               
             
          
           
               
                 No. 
                 T m   
                 Zone 1 
                 Zone 2 
                 Zone 3 
                 Spinhead 
                 ° C. 
               
               
                   
               
               
                 P-I-D 
                 46, 
                 140 
                 175 
                 228 
                 230 
                 5-6 X @ 45-60 
               
               
                   
                 218 
                   
                   
                   
                   
                   
               
               
                 P-II-A 
                 124 
                 140 
                 177 
                 228 
                 230 
                 5-6 X @ 45-60 
               
               
                 p-III-C 
                 42, 
                 130 
                 168 
                 207 
                 210 
                 6-8 X @ 55-70 
               
               
                   
                 158 
                   
                   
                   
                   
                   
               
               
                 P-III-E 
                 45, 
                 130 
                 165 
                 208 
                 210 
                 6-10 X @ 45-60  
               
               
                   
                 150 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE V 
               
             
             
               
                   
               
               
                 Suture Properties of Typical Monofilaments 
               
             
          
           
               
                   
                 Polymer Number 
               
             
          
           
               
                   
                 P-I-D 
                 P-II-A 
                 P-III-C 
                 P-III-E 
               
               
                   
                 (USG9) 
                 (USG10) 
                 (USL5) 
                 (USL6) 
               
               
                   
               
             
          
           
               
                 Physical Properties 
                   
                   
                   
                   
               
               
                 Diameter, mm 
                 0.45 
                 0.46 
                 0.28 
                 0.28 
               
               
                 Initial Strength, Kpsi 
                 56.9 
                 67.8 
                 45.3 
                 35.9 
               
               
                 N 
                 65.6 
                 78.7 
                 19.5 
                 15.9 
               
               
                 Modulus, Kpsi 
                 21 
                 50 
                 256 
                 153 
               
               
                 Elongation, % 
                 109 
                 103 
                 99 
                 137 
               
               
                 Knot Strength, N 
                 52.9 
                 53.7 
                 17.7 
                 14.4 
               
               
                 Water Absorption/Swelling 
                   
                   
                   
                   
               
               
                 Data 
                   
                   
                   
                   
               
               
                 Increase in Diameter,  
                 2.6/1, 4.5/18 
                 1.1/1, 2.1/18 
                  8.4/1 
                 12.9/1 
               
               
                 %/hour 
                   
                   
                   
                   
               
               
                 Increase in volume, %/hour 
                 5.3/1, 9.1/18 
                 2.2/1, 4.3/18 
                 17.14/1 
                 27.4/1 
               
               
                 In Vitro BSR, % @ 
                   
                   
                   
                   
               
               
                 Day 3 
                 76 
                 79 
                 — 
                 — 
               
               
                 Week 1 
                 35 
                 53 
                 69 
                 57 
               
               
                 Week 2 
                 3 
                 16 
                 57 
                 52 
               
               
                 Week 3 
                 — 
                 — 
                 50 
                 — 
               
               
                 In Vivo BSR, % @ 
                   
                   
                   
                   
               
               
                 Week 1 
                 45 (62) 
                 61 (62) 
                 — 
                 — 
               
               
                 (traditional polyester of 
                   
                   
                   
                   
               
               
                 similar composition) 
                   
                   
                   
                   
               
               
                 Week 2 
                  6 (30) 
                 30 (30) 
                 — 
                 — 
               
               
                 (traditional polyester of 
                   
                   
                   
                   
               
               
                 similar composition) 
                   
                   
                   
                   
               
               
                 Accelerated In Vitro Mass 
                 6 hours 
                 2.5 days 
                 — 
                 — 
               
               
                 Loss, Time to ~50% Mass 
                 (9 days) 
                 (9 days) 
                   
                   
               
               
                 Loss (traditional polyester  
                   
                   
                   
                   
               
               
                 of similar composition) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE VI 
               
             
             
               
                   
               
               
                 Properties of Electrospun Fabrics Prepared 
               
               
                 from Typical Block Copolymers 
               
             
          
           
               
                   
                 Thermal 
                   
                   
                   
                   
               
               
                   
                 Characteristics 
                 Burst 
                 Deflection 
                 Contact 
                 Inherent 
               
             
          
           
               
                   
                 T g   
                 ΔH f   
                 T m   
                 Strength 
                 at Burst 
                 Angle 
                 Viscosity 
               
               
                 Polymer 
                 (° C.) 
                 (J/g) 
                 (° C.) 
                 (N/mm) 
                 (mm) 
                 (°) 
                 (dL/g) 
               
               
                   
               
             
          
           
               
                 P-I-F 
                 71 
                 22.8 
                 158 
                 100 
                 25 
                 131 
                 1.52 
               
               
                 P-I-G 
                 60 
                 30.6 
                 158 
                 61 
                 24 
                 135 
                 0.99 
               
               
                 P-I-H 
                 63 
                 28.7 
                 159 
                 48 
                 33 
                 137 
                 1.43 
               
               
                 P-I-I 
                 61 
                 28.7 
                 159 
                 104 
                 27 
                 121 
                 1.51 
               
               
                   
               
             
          
         
       
     
     Preferred embodiments of the invention have been described using specific terms and devices. The words and terms used are for illustrative purposes only. The words and terms are words and terms of description, rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill art without departing from the spirit or scope of the invention, which is set forth in the following claims. In addition it should be understood that aspects of the various embodiments may be interchanged in whole or in part. Therefore, the spirit and scope of the appended claims should not be limited to descriptions and examples herein.