bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of biodegradable hydrogels for colon‐specific drug delivery
Authors: Hovgaard Lars , Brøndsted Helle
Published: March 2011

This paper summarizes the work carried out in our group over the last five years on biodegradable dextran hydrogels for colon‐specific drug delivery. Emphasis is placed on the recent developments in the design of dextran hydrogel capsules. The dextran hydrogels were shown to remain intact in the stomach and small intestine but were degraded by microbial dextranases in the colon. A large number of hydrogels with different structures have been studied and characterized in detail with respect to crosslinking density, equilibrium degree of swelling and modulus of elasticity. The release of hydrophilic and hydrophobic model drug molecules from dextran hydrogel discs and capsules have been studied. Biodegradation of the hydrogels was studied using a pure dextranase preparation, in vivo in rats and in vitro in human colon. Degradability was evaluated by measuring the time for complete dissolution of the hydrogels, the change in thickness and dry weight of the hydrogel discs and the production of short‐chain fatty acids. The surface characteristics of gels before and after degradation were studied by scanning electron microscopy.
Polymer liquid dynamics studied via dielectric normal mode spectroscopy
Authors: Kotaka Tadao , Adachi Keiichiro
Published: March 2011

Dielectric spectroscopy was applied to study dynamics of cis‐polyisoprenes (PI), used as type‐A probe, in blends with polybutadiene (PB) and in block copolymers with polystyrene (PS) of SI‐ and SIS‐type. For dilute high‐molecular weight (M) PI/low‐ M PB blends we identified Rouse mode with M2‐dependent relaxation time τ, while for low‐ M Pi/high‐ M PB blends, we identified pure reptation mode with M3 ‐dependent τ. In between τ ∞ Mα with the exponent α varying from 2 to 3 as MB was increased, as suggested by Graessley with constraint release via tube renewal mechanism. For the blends with the MW ratio MI/MB = 2.5, we found bulk polymer behaviour with τ ∞ M3.5, in which competition between pure reptation and tube renewal appear to be essential and the contribution of contour length fluctuation may be ruled out. For SI‐diblock copolymers between Tg(I) < T < Tg(S) we observed normal modes of I‐block chains tethered on rigid S‐domains. The mode distribution as judged from the dielectric loss ε” curves was dependent on the domain morphology, reflecting restricted motions of crowded I‐tethered chains. For SIS‐triblock copolymers normal modes became appreciable, even below their critical solution temperature, in the range of T > Tg(S), exhibiting broadening due presumably to their micro‐phase‐separated structure. The relaxation mechanisms for such end‐capped I‐chains in SIS‐triblock copolymers could be junction hopping in those with isolated S‐domains but chain rotating in those with S continuous morphologies.
Orientation of amorphous polymers
Authors: Monnerie L. , Jasse B. , Bokobza L.
Published: March 2011

Orientation of amorphous polymers stretched at a temperature above their glass‐transition temperature, is involved in thermoforming processing.

The molecular processes controlling the orientation and chain relaxation of polymers have been investigated by infrared dichroism in a large series of materials: polystyrene, polymethylmethacrylate of various tacticity and its copolymers with styrene and acrylonitrile.

Polystyrene with hydrogenated and deuterated blocks leads to information on the behavior of each block (central part, chain ends) and allows a quantitative comparison with the Doi‐Edwards model for chain relaxation. In order to analyse the effect of polydispersity, blends of hydrogenated and deuerated polystyrene chains with various molecular weights have been studied. Short chains with molecular weights smaller than the molecular weight between entanglements, enhance the relaxation of long chains. Furthermore an anisotropic orientational coupling effect exists between a chain segment and its oriented surrounding.

By comparing the orientation of polymers with different chemical structures, it results that they behave differently under temperature conditions where T ‐ Tg = const, but they undergo identical relaxations when the experiments are performed at temperatures chosen in such a way that the monomer friction coefficients are identical.

In copolymers of styrene and methylmethacrylate, the two monomer units have different orientations due to local conformational constraints. This effect also accounts for the difference observed between an alternated and a random copolymer.
Improved red dopants for organic electroluminescent devices
Authors: Chen C. H. , Tang C. W. , Shi J. , Klubek K. P.
Published: March 2011

A t‐butyl substituted red fluorescent dye, 4‐(dicyanomethylene)‐2‐t‐butyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJTB), has been found to be an excellent dopant in AIQ3 which produces a highly efficient organic EL device with improved red chromaticity. Unlike 4‐(dicyanomethylene)‐2‐methyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJT), DCJTB can be synthesized in a pure form directly from the unsymmetrical 4‐(dicyanomethylene)‐2‐(t‐butyl)‐6‐methyl‐4H‐pyran without the contamination of the non‐fluorescent bis‐condensation byproduct which is prevalent in the DCJT preparation. Both photoluminescence and electroluminescence in the solid films of DCJTB in AlQ3 are modestly enhanced by the extra t‐butyl substitution as a result of a reduction in the effect of concentration quenching. The operation stability of the DCJTB doped EL device is superior, having a half‐life of over 5,000 h driven at an initial brightness > 400 cd/m2.
Improved stability of molecular organic EL devices
Authors: Fujii Hiroyuki , Sano Takeshi , Nishio Yoshitaka , Hamada Yuji , Shibata Kenichi
Published: March 2011

Influence of emission sites on emission efficiency and running durability of molecular organic electroluminescent devices was investigated. When fluorescent dye rubrene was doped into TPD diamine hole transport layer, rubrene molecule emitted bright yellow light with a max. luminance of 61 000 cd/m2. The device had the highest efficiency of 9.8 Im/W at 100 cd/m2. Half‐decay time of the device from initial luminance of 530 cd/m2 under constant direct current was 3 600 h. On the other hand, when rubrene was doped into BeBq2 complex electron transport layer, the efficiency was 4.4 Im/W and the half‐decay time was 110 h. Thus doping site is found to exert significant influence both on the emission efficiency and the running durability.
Synthesis and properties of novel hole transport materials for electroluminescent devices
Authors: Thelakkat Mukundan , Fink Ralf , Haubner Frank , Schmidt Hans‐Werner
Published: March 2011

We synthesized low molecular weight triphenyldiamines (TPDs), novel 1,3,5‐tris(diarylamino)benzenes (TDABs), polymeric triphenyldiamines and insoluble triphenylamine networks based on tris(4‐ethynylphenyl)amine as hole transport materials for electroluminescent displays. The HOMO energy values as determined from cyclic voltammetry measurements for TPDs and TDABs are between −4.97 and −5.16 eV. By using a polymeric TPD as hole transport layer and tris(8‐quinolinolato) aluminium as emitter, LEDs with an onset voltage of 3V and a luminance up to 900 cd/m2 were obtained under ambient conditions.
A general approach to precursors for poly(arylene vinylene) derivatives: Mechanism, scope and modifications
Authors: Vanderzande Dirk J. , Issaris Anna C. , van Der Michael J. , Borght Albert , van Breemen J. , De Kok Margreet M. , Gelan Jan M.
Published: March 2011

A new precursor route for poly(arylene vinylene) derivatives will be presented. In this way non‐ionic precursor polymers are obtained which show an enhanced thermal stability and are soluble in organic solvents. This enables a thorough structural characterization and the study of the mechanism. Experiments have been performed to differentiate between a radical or an ionic polymerization mechanism. Furthermore possibilities to tune solubility characteristics and to introduce defects in the polymer backbone will be discussed. Also the scope for this new route was explored. The first results indicate that the versatility exceeds that of the Wessling route, e.g. the synthesis of precursors for poly(p‐biphenylene vinylene) and poly(2,6‐naphthylene vinylene) could be accomplished in our case, whereas it failed in the case of the Wessling route.
Modification of polymers by adsorption phenomena
Authors: Weidenhammer Petra , Jacobasch Hans‐Jörg
Published: March 2011

The adsorption of ions and amphiphilic molecules on solid polymers is investigated by direct force measurements using an atomic force microscope (AFM). It is shown that electrolyte ions are changing the surface potentials of the solid polymers as well as their adhesive properties. The experiments show that the interaction with a negatively charged probe is dramatically decreased by the adsorption of anions. The adsorption isotherms are determined by zeta potential measurements (streaming potential of flat plates). In presence of adsorbing anions, the attractive interaction and the adhesion are reduced and can be eliminated completely.

So, even solutions of simple electrolyte ions can be applied intentionally in order to modify the interaction of polymer surfaces. A wide variety of technological applications becomes accessible.
The combination of ionic surfactants with polyelectrolytes‐a new material for membranes?
Authors: Schwarz Hans‐Hartmut , Richau Klaus , Apostel Regine
Published: March 2011

The combination of two oppositely charged polyelectrolytes results in polyelectrolyte complexes. The simultaneous interfacial reaction between the different polyions leads to formation of polyelectrolyte complex membranes. Some of these have a very good performance in the membrane process pervaporation, especially for dehydration of organic liquids. The combination of a polyelectrolyte with an ionic surfactant of opposite charge results like‐wise membranes but with other separation properties. The differences between the two types of membranes, formed from cellulosesulfate in combination with cationic polyelectrolytes or cationic surfactants, will be discussed.
Multilayers by adsorption of functional polyelectrolytes
Authors: Charlier Valery , Laschewsky André , Mayer Bernd , Wischerhoff Erik
Published: March 2011

The synthesis of polycations bearing reactive groups, namely tertiary anilines located in the side chain or in the main chain, is described. These polyions are employed in conventional alternating polyelectrolyte multilayer assembly or in a modified build‐up process including an azo coupling reaction on the topmost layer after every polycation adsorption step, which offers the potential to create multilayer structures with a non‐centrosymmetric structure. The characterization of these modified assemblies by UV/VIS spectroscopy reveals significant differences in the spectral data in dependence of the polycation structure.
Anew technique for determining the adsorption energy of terminally adsorbed polymer
Authors: Chen Ming‐Hua , Furusawa Kunio
Published: March 2011

Using a new experimental technique, “Continuous Elution Method”, the desorption behavior of polystyrene(PS) and polystyrene (PS‐X) functionalized by a terminal iminium ion (‐X) from α‐Al2O3 and γ‐Al2O3 surface were investigated, and found that PS‐X is forming a terminally adsorbed polymer layer on α‐Al2O3, surface. Furthermore, it was found that the adsorption force of terminally adsorbed polymer is balanced with the desorption force which is contributed from the osmotic pressure in the adsorption layer. Based on this concept, the adsorption energy of the end‐functionalized polystyrene terminally adsorbed on the α‐Al2O3, surface was evaluated to be 4.2 ˜4.3 kT.
Application of cationic polymerization to grafting and coating of silica particles
Authors: Spange Stefan , Eismann Ulrike , Höhne Susanne , Langhammer Elke
Published: March 2011

The cationic polymerization of electron rich monomers such as vinyl ethers, vinyl furane, and cyclopentadiene on silica surfaces can be initiated by aryl methyl halides. The reactions yield always soluble polymers (by heterogeneous catalysis) and novel polymer/silica hybrid materials. The link between polymer and solid is caused by covalent Si‐O‐C bonds, by network formation of the polymers during the chain growth, or by a combination of both of them. The analysis of the polymer structures on the surface by 1H MAS NMR spectroscopy in suspension and by solid state 13C CP MAS NMR spectroscopy is described. Proof of Si‐O‐C bonds via DRIFT spectroscopy and 13C CP MAS NMR spectroscopy is given. The most effective method of irreversibly linking the polymer to the silica surface is the network formation. Polyvinyl ethers are bound strongly to the surface, as can be shown by FTIR measurements, but the linkage is not stable due to the Si‐O‐C bonds' susceptibility to hydrolysis.

Poly‐cyclopentadienes (PCPD) are linked to the surface by Si‐O‐C bonds, which show an extraordinary high resistance to acids and bases. Si‐O‐C bond formation of poly‐2‐vinyl furane could not yet be detected by 13C CP MAS NMR spectroscopy and DRIFT spectroscopy. In this case the high degree of coating derives from the bifunctionality of 2‐vinyl furane: it may undergo Friedel‐Crafts‐alkylation at the 5‐position of the furane ring as well as chain polymerization via the vinyl group at the 2‐position.
Direct filature of bacterial cellulose from culture medium
Authors: Tokura Seiichi , Asano Hisashi , Sakairi Nobuo , Nishi Norio
Published: March 2011

The continuous Filature of bacterial cellulose has been achieved directly from culture medium using shallow culture pan newly designed. A remarkable progress of fiber properties was observed comparing with regenerated cellulosic filaments on the filament of bacterial cellulose dependently on the rinsing process with water or ethylene glycol. The progress of fiber properties was also shown on the filament of N‐acetylglucosamine(GlcNAc) incorporated bacterial cellulose probably due to enforcement of fiber interactions. A copolymer of carboxymethylglucose (CM‐Glc) and glucose has been achieved successfully to increase the adsorption capacity for lead ion comparing with original carboxymethyl cellulose (CMC).
Industrial proteins as a green alternative for ‘petro’ polymers: Potentials and limitations
Authors: De Graaf Leontine A. , Kolster Peter
Published: March 2011

For the development of technical applications of polymers from renewable resources, various biopolymers are being studied. In this paper, the opportunities for industrial proteins on this market are discussed e.g. for use in (technical) coatings, adhesives, surfactants and plastics. The use of protein modifications for the improvement of functional properties relevant for technical applications is addressed.
Development and application of highly efficient ruthenium‐based catalysts for the ring opening metathesis polymerization
Authors: Glander S. C. , Nuyken O. , Schattenmann W. C. , Herrmann W. A.
Published: March 2011

Various bisallylic ruthenium(IV) complexes were synthesized and tested as catalysts for the ring opening metathesis polymerization (ROMP) of norbornene. In presence of cocatalysts such as silanes or certain diazoalkanes a significant increase of the catalytic activity could be observed. With these highly efficient systems the ROMP of diolefinic norbornene derivatives (dicyclopentadiene, 5‐ethylidene‐2‐norbornene, norbornadiene) and monomers containing functional groups was achieved (e.g. alcohols, acids, esters, amides, imides, ketones, aldehydes, …).
Copolymerization of CO2 and cyclohexene oxide
Authors: Super M. , Beckman E. J.
Published: March 2011

Generation of high value polymers from carbon dioxide is of general technological interest given that CO2 is both inexpensive and relatively easy to handle on an industrial scale. Previous work on the use of CO2 as a comonomer has focused primarily on development of new catalysts, and the effects of conventional process variables such as temperature and concentration on the polymerization outcome have not been examined in great detail. Recently, we, as well as Darensbourg and colleagues, have shown that one can generate zinc‐based catalysts for the polymerization of CO2 and cyclohexene oxide which produce over 400 grams of polymer per gram of metal. In this paper, we use a product of the reaction between zinc oxide and the fluorinated half‐ester of maleic anhydride to generate copolymers of CO2 and cyclohexene oxide where CO2 is both reactant and sole solvent. In general, we found that the outcome of the polymerization depends greatly on the proximity to the ceiling temperature and the critical cyclohexene oxide concentration, and also on the phase behavior of the cyclohexene oxide‐CO2 binary.
Effect of thermooxidation on tinuvin 783 in LDPE films: Characterization by UV and ftir spectroscopy
Authors: Kaci Mustapha , Rezgui Farouk , Sadoun Tahar
Published: March 2011

The effect of thermooxidation on Tinuvin 783 which is a hindered amine light stabilizer in LDPE films has been investigated by UV and FTIR spectroscopy. Initially, a standard curve describing the variation of the concentration of Tinuvin 783 in LDPE films was plotted using the method of integration of the band area. The relation obtained was: band area = 19.6249 × [Tinuvin 783]. This equation was then applied to measure the variation of the concentration of Tinuvin 783 in the 0.2%wt stabilized samples which have undergone thermooxidation at 90°C for 98 days. The results showed a considerable decrease in the concentration of Tinuvin 783 by 35% during the first 30 days due to probably the formation of nitroxyl radicals. After this, the concentration was observed to be unchanged and may correspond to the phase of nitroxyl radical regeneration. On the other hand, no chemical change in the stabilized LDPE films was observed by FTIR spectroscopy at 90°C during 98 days while the band characteristic of ketone groups (1720 cm−1) was detected for the unstabilized samples after only 11 days. (LDPE: low density polyethylene; HALS: hindered amine light stabilizer)
Recent developments in rubber processing, leading to new applications such as the “green tyre”
Authors: Noordermeer Jacques W. M.
Published: March 2011

Rubber articles derive most of their mechanical properties from the admixture of reinforcing fillers. Most commonly, carbon black is used as reinforcing filler. If silica is used instead, tyres made with such rubber compounds may exhibit a rolling resistance reduction by ca. 30%, which translates in substantial fuel savings of a car. Such silicas are far more difficult to mix with rubber than carbon black. Coupling agents are used as a surface modification of the filler to enhance compatibility with the polymer. Additionally they improve the ease of mixing with the rubber. The development of proper coupling agents combined with improved mixing techniques has contributed to the final break‐through of the silicareinforced “Green Tyre”.
Thermoplastic composites based on flax fibres and polypropylene: Influence of fibre length and fibre volume fraction on mechanical properties
Authors: Peijs Ton , Garkhail Sanjeev , Heijenrath Rob , van Den Oever Martien , Bos Harriëtte
Published: March 2011

Natural‐fibre‐mat‐reinforced thermoplastic (NMT) composites based on flax fibre mats and a Polypropylene (PP) matrix were manufactured using (i) a film‐stacking method and (ii) a paper making process. The influence of fibre length and fibre content on stiffness and strength is reported and compared with data for glass‐mat‐reinforced thermoplastic (GMT) composites, including the influence of using maleic‐anhydride grafted PP. The data is also compared with existing micromechanical models like Kelly‐Tyson and Cox‐Krenchel for strength and stiffness, respectively. A good agreement was found between theory and experiment in case of stiffness while in case of strength the experimental values fall well below the theoretical predictions. Results indicated that NMTs are of interest for low‐cost engineering applications and can compete with commercial GMTs, especially when a high stiffness per unit weight is desirable. Results also indicated that the key area for future development lies not only in improved adhesion but mainly in improving the fibre strength.
Solid‐state processing of phb‐powders
Authors: Lüpke Thomas , Radusch Hans‐Joachim , Metzner Klaus
Published: March 2011

Poly(3‐hydroxybutyrate) (PHB) is a completely biodegradable polyester, produced by bacterial fermentation. Because of poor thermal stability, melt processing of the material is accompanied by thermal degradation and poor mechanical properties.

To prevent thermal degradation, a solid‐state processing technology has been applied. The extrusion of PHB‐powder at temperatures far below the melting point leads to products of improved mechanical properties. In particular, the ductility of the material increases considerably compared to traditional melt processed PHB. The improved mechanical properties have been attributed to structural differences on the molecular and supermolecular level.
Surface modification of polypropylene: Hydrophilic finishing with carbohydrates
Authors: Knaus Simone , Nennadal Andrea
Published: March 2011

Conversion of hydrophobic polypropylene surfaces to hydrophilic, water wettable surfaces by adsorption of amphiphilic carbohydrates (“surfactant immobilization”) as well as by covalent bonding of sucrose residues via azid photolysis (“photochemical immobilization”) was investigated. Improvement of surface hydrophilicity was determined by contact angle measurements and application of special test inks for polyolefines.
Polymerization of 1,3‐dienes with neodymium catalysts
Authors: Porri Lido , Ricci Giovanni , Shubin Nikolai
Published: March 2011

Neodymium catalysts are typical for the cis polymerization of 1,3‐dienes. The systems prepared from a neodymium‐carboxylate, a chlorine donor and A1(i‐C4H9)3 are characterized by a low efficiency, only ca. 6% of the neodymium being active in the catalysis. Much more active systems are obtained using allyl derivatives of neodymium in combination with aluminoxanes, in particular with methylaluminoxane (MAO). These systems have the characteristics of a single site catalyst. Evidence suggesting an ionic structure for the catalytic species is reported. Terminally substituted butadienes give polymers with a cis‐1,4 isotactic structure, with the exception of (E, E)‐2,4‐hexadiene, which gives trans‐1,4 polymers. An interpretation is reported.
Reactions with samarium diiodide in polymer synthesis
Authors: Vygodskii Yakov S.
Published: March 2011

Reactions induced by Sml2, such as reduction, coupling and cyclization are occurring in high yield upon mild conditions. It is due to the high redox potential of divalent samarium. Now reactions with Sml2 are used in the polymer synthesis as well. By the coupling reaction of various diacid chlorides poly‐α‐diketones having molecular weight up to 20000 have been obtained at room temperature in quantitative yield. Isomeric difluorobenzils prepared by the one‐step reaction of Sml2 and relevant fluorobenzoyl chlorides have been used in the nucleophylic substitution reaction with bisphenols. Film‐forming high molecular weight copolyetherketone‐α‐diketones have been synthesized when such difluorobenzils have been used as the comonomers in the polycondensation of 4,4'‐difluorobenzophenone and bisphenols. All these polymers bearing α‐diketogroups have been transformed into linear and network polyquinoxalines by their reaction with aromatic (bis)o‐diamines. Aromatic polypinacols have been synthesized by the reaction of dialdehydes and Sml2 in THF under mild conditions. The availability of the reactive α‐hydroxy groups made it possible to carry out polymer chain reactions. It was stated that the imide cycle is reduced by Sml2 at room temperature. The treatment of polyimides by Sml2 leads to the change of polymer properties, mainly heat resistance and solubility. The possibility of formation of Si‐Si bonds by reductive coupling of organochlorosilanes with the use of Sml2 instead of Na has been shown. It was found that the reaction of diorganodichlorosilanes with Sml2 easily proceeds in THF solution at room temperature to yield α,ω‐dichloro‐oligosilanes.
Synthesis of “living” chains of polyvinylpyridine and their application to the construction of homo‐ and hybrid polymer with complex architecture
Authors: Erussalimsky Boris L. , Fedorova Lyubov A. , Klenin Stanislav I. , Shibaev Lev A.
Published: March 2011

Experimental conditions ensuring the formation of living poly(2‐ and 4‐vinyl pyridine) chains in the vinyl pyridine ‐ allyl derivatives of chromium, molybdenum and tungsten systems are described. Variation of the reagents nature, polarity of the solvent permits to obtain polymers differing in their structural and molecular parameters. Synthesized polymers contain block and graft sequences, as well as macrocyclic fragments. Living chains under consideration were applied for polymerization of different monomers. Hybrid polymers obtained by this way were studied in detail by the same methods as the homopolymers.
Design and preparation of liquid crystalline block copolymers
Authors: Chiellini E. , Galli G. , Angeloni A.S. , Laus M.
Published: March 2011

The design and preparation of liquid crystalline (LC) block copolymers by use of azo‐macroinitiators are outlined. This approach is very versatile and makes it possible to realize diverse architectures of block copolymers, including non‐LC/side‐chain, non‐LC/main‐chain and side‐chain/main‐chain block copolymers. The different blocks were phase separated and underwent their individual phase transitions. In side‐chain/main‐chain block copolymers different LC mesophases coexisted in equilibrium.
Miscibility of crystalline and amorphous polymers: Poly‐ethylene/polyisobutylene blends
Authors: Szabó Péter , Pukánszky Béla
Published: March 2011

Blends were prepared from a linear low density polyethylene and a polyisobutylene in the entire composition range. Flory‐Huggins interaction parameters were determined from DMTA and DSC measurements. The usual technique had to be modified in the case of DSC data, since the Tg of PE cannot be determined by this technique. The two methods yielded identical results and indicated good interaction of the components, which was supported also by a SEM study and the mechanical properties of the blends.
Uniform polyolefin and polymethacrylate
Authors: Hatada Koichi , Kitayama Tatsuki , Ute Koichi , Nishiura Takafumi
Published: March 2011

Preparations and properties of synthetic uniform polyolefins and polymethacrylates are described with emphasizing the necessity of their utilization for understanding the fundamental problems in polymer chemistry. Uniform polymer is a polymer composed of molecules uniform with respect to molecular weight and constitution. While classical organic chemistry provides means of constructing uniform polymers such as poly(methylene)s in stepwise manners, recent advances in separation technology such as supercritical fluid chromatography (SFC) have made it possible to isolate synthetic uniform polymers from its homologous mixture. Combinations of stereospecific polymerizations and the SFC technique have enabled us to prepare uniform polystyrenes and poly(methyl methacrylate)s with high stereoregularities, which are very useful for systematic studies on the nature of polymers. The thermal properties of these uniform polymers are discussed in some detail.
Amino acid functionalized ionomeric materials in biomedical applications
Authors: Culbertson Bill M. , Xie Dong , Thakur Alka
Published: March 2011

Several N‐acryloyl and N‐methacryloyl substituted amino acids have been prepared and copolymerized with acrylic acid and itaconic acid to prepare new polyelectrolytes. Due to an acid‐base reaction, mixing of the water soluble copolymers with glass powders, having leachable Ca2+, Al3+, etc., type cations, produces inorganic‐organic composites hardened by salt ‐bridge formation. These heretofore unexplored polyelectrolytes are shown to be very useful for preparing improved dental biomaterials.
Macromolecular metal complexes with memory to the catalyzed substrate
Authors: Efendiev Aiaz A.
Published: March 2011

A number of complexing polymers containing carboxylic, phosphorylic, amine, imine and pyridine functional groups have been prepared and their complexes with copper, cobalt and nickel have been obtained. The complexes were prearranged for reactions of liquid phase oxidation and hydrogenation of hydrocarbons by means of formation and subsequent fixation in memory of the catalysts the structure of active centres favorable for catalyzed substrate. It has been shown that the prearranged complexes might ≤remember≥ the structure optimum for the substrate and this leads to an essential increase in catalytic activity and selectivity of the catalysts.
Two‐phase wacker oxidation of alkenes catalyzed by water‐soluble macromolecular complexes of palladium
Authors: Karakhanov Edward , Filippova Tatyana , Maximov Anton , Predeina Viktoriya , Restakyan Anna
Published: March 2011

New water‐soluble macromolecular palladium complexes with phase transfer ability were used for two‐phase Wacker oxidation of higher alkenes. Macromolecular metal complexes have been prepared employing as ligands monobutyl ether of polyethylene oxide and copolymers of ethylene oxide and propylene oxide functionalized by β,β'‐iminodipropionitrile and acetodinitrile. Macromolecular metal complexes exhibited high activity and selectivity as catalysts for Wacker oxidation of different alkenes: octene‐1, dodecene‐1, hexadecene‐1, styrene, propenylbenzene, cyclooctadiene‐1,5. The complexes based on β,β'‐iminodipropionitrile ligands showed the highest activity. All catalysts can be easily separated from product and used repeatedly without decrease of activity.
Polymeric cobalt‐schiff‐base and ‐porphyrin complexes as a dioxygen device
Authors: Nishide Hiroyuki , Tsukahara Yukihiro , Suzuki Yoko , Tsuchida Eishun
Published: March 2011

New functions of polymeric cobalt complexes were examined using their oxygen‐binding reactions in the solid state. An oxygen‐releasing device was prepared by compositing the oxygen‐binding but electrically insulating cobalt‐Schiff‐base or ‐porphyrin complex with a conductive carbon powder. The device quickly released the absorbed oxygen in response to an applied voltage. A polymer film containing the cobalt‐Schiff‐base complex reversibly stretched in response to the atmospheric oxygen concentration. The driving force of the stretching of the film was attributed to the crystal structure change of the complex before and after the oxygen‐binding.
Nanosize metallodendrimers
Authors: van Veggel Frank C. J. M. , Huck Wilhelm T. S. , Reinhoudt David N.
Published: March 2011

Building blocks have been designed for the non‐covalent formation of nanosize assemblies. As non‐covalent interactions coordination chemistry and hydrogen bonding have been used. The self‐assembly process leads to spherical assemblies with diameters in the range of 100 to 400 nm, with standard deviations in the order of 10–15%. The controlled assembly approach allows a precise controll of size and assemblies with molecular weights up to 10,000 Dalton have been realized. Finally, we have developed a strategy in which hydrogen bonding and coordination chemistry can be applied “orthogonally”
Model kinetic study of TiCl4‐induced ionization of polyisobutene capped with diphenylethylene application to the synthesis of block copolymers
Authors: Charleux Bernadette , Moreau Michel , Vairon Jean‐Pierre , Hadjikyriacou Savvas , Faust Rudolf
Published: March 2011

The use of non‐homopolymerizable monomers such as 1,1‐diphenylethylene (DPE) in the synthesis of functional polymers and block copolymers by cationic polymerization has been recently reported. The most important parameters in this process, the kinetics and extent of ionization and capping as well as the stability of the cation, were investigated by studying the reaction with TiCl4 of 1‐methoxy‐1,1‐diphenyl‐3,3,5,5‐tetramethylhexane, a model for DPE‐capped polyisobutene chain‐end. This study was performed using 1H NMR and the high‐purity stopped‐flow device coupled with UV‐visible spectroscopy.
Poly(vinyl ethers) as building blocks for new materials
Authors: Goethals Eric J. , Reyntjens Wouter , Lievens Serge
Published: March 2011

The living cationic polymerization of vinyl ethers has been used to prepare a number of new polymers with special properties. Sequential polymerization of the hydrophilic methyl vinyl ether (MVE) and the hydrophobic octadecyl vinyl ether (ODVE) has lead to amphiphilic block‐copolymers with emulsifying properties for water/decane mixtures. Poly(vinyl‐ether) macromonomers were obtained by end‐capping of living polymers with hydroxyethyl acrylate. Copolymerization of polyODVE‐macromonomer with usual acrylates lead to highly branched hydrophobic polymers. When the end‐capping was performed with bifunctionally living polymers, the corresponding “bis‐macromonomers” were obtained. Copolymerization of such bis‐macromonomers with styrene or butyl acrylate, leads to the formation of segmented polymer networks. In the case of polyODVE‐poly(butyl acrylate), these networks showed a pronounced phase separation. Due to the crystallinity of the polyODVE domains, these materials showed shape memory properties.
Open mechanistic problems of quasiliving carbocationic polymerization of olefins mediated by nucleophilic additives
Authors: Iván Béla
Published: March 2011

This study is a comprehensive overview of the open problems and the existing views on the mechanism of quasiliving carbocationic polymerizations (QLCP) of olefins mediated by nucleophilic additives. The fundamental and general aspects of ideal living and quasiliving polymerizations involving other mechanisms, such as free radical, group transfer, ring‐opening metathesis, ring‐opening cationic and anionic processes, have been also analyzed and summarized. Quasiliving carbocationic polymerization of olefins in the presence of nucleophiles, which form complexes with the Lewis acid coinitiators, occur By reversible termination. Four different mechanisms have been discussed in this study: (1) reactivity leveling by nucleophiles (“electron donors”); (2) propagation by species with decreased ionicity (“stretched polarized bonds”) mediated by Lewis acid‐nucleophile complexes (LA‐Nu); (3) propagation by classical ion pair and free ion species; (4) proton scavenging by nucleophiles and 2,6‐di‐teri‐butylpyridine proton trap. It is shown that mechanisms No. 1, 3 and 4 cannot explain all the existing findings, and although the experimental results can be interpreted with mechanism No. 2, the existence of “stretched polarized bonds” can be questionable. It is also concluded that compared to nonliving carbocationic polymerization, kinetic analysis indicates that the propagating species cannot be the same in quasiliving carbocationic polymerizations and in chain transfer dominated classical carbocationic polymerizations with ion pairs and free ions.
Transformation of “living” carbocationic and other polymerizations to controlled/“living” radical polymerization
Authors: Matyjaszewski Krzysztof
Published: March 2011

Transformation of “living” carbocationic polymerization of styrene and isobutene to controlled atom transfer radical polymerization (ATRP) is described and formation of the corresponding AB and ABA block copolymers with styrene (St), methyl methacrylate (MMA, methyl acrylate (MA) and isobornyl acrylate (IBA) was demonstrated. A similar approach was applied to the cationic ring opening polymerization of tetrahydrofuran leading to the AB and ABA block copolymers with St, MMA and MA using ATRP. Site transformation approach was also used for the ring opening metathesis polymerization of norbornene and polycondensation systems using polysulfone as an example. In both cases, AB and ABA block copolymers were efficiently formed with styrene and acrylates.
Specific solvent effects of dioxane and N,N,N′,N′‐tetramethylethylenediamine in the anionic polymerization of styrene with Li+ as counterion
Authors: Bastiaens Jos , Huyskens Pierre , van Beylen Marcel
Published: March 2011

The anionic propagation of living polystyryllithium shows a distinctly different behavior depending on the nature of the solvent used (polar or non‐polar). To demonstrate the transition of one type of behavior to the other, studies have been carried out in the past in mixtures of benzene and tetrahydrofuran (THF) and mixtures of dioxane and THF.
Synthesis of homo‐ amd block copolymer multi‐armed methacrylic star polymers by triisobutylaluminium/tert‐butlyllithium initiation
Authors: Crossman Martin C. , Haddleton David M.
Published: March 2011

Methacrylate star polymers were prepared using the “arm‐first” strategy of star polymer formation by the addition of ethylene glycol dimethacrylate to living linear poly(methacrylate) arms synthesised by a trialkylaluminium/alkyllithium initiating system Control over star molar mass is discussed for poly(methyl methacrylate) armed star polymers as is the preparation of star polymers with block copolymer arms.
Novel initiating systems for the living polymerization of acrylates and methacrylates
Authors: Schlaad Helmut , Schmitt Bardo , Müller Axel H. E. , Jüngling Stephan , Weiss Horst
Published: March 2011

The polymerization of methyl methacrylate with lithiated initiators in the presence of aluminium alkyls in toluene has living character but it deviates from conventional first‐order kinetics and the polymers have fairly broad molecular weight distributions. This results from the formation and precipitation of a coordinative polymer network in which the lithium ions of the living chain ends are coordinated to the in‐chain ester carbonyl groups. Thus, the network formation can be prevented by adding Lewis bases like methyl pivalate which coordinate to the living chain ends instead of the polymer. Alternatively, one can introduce tetraalkylammonium salts aiming at an exchange of the lithium ion by a less electropositive cation. Both approaches lead to linear first‐order time conversion plots for the polymerization of methacrylates and acrylates and to narrow molecular weight distributions, i.e., to a living and controlled polymerization. With these new initiating systems, various block and graft copolymers can be synthesized.
Living anionic polymerization of (meth)acrylic esters: New mechanistic concepts and resulting materials
Authors: Teyssié Philippe , Baran Janusz , Dubois Philippe , Jérǒme Robert , Wang Jin‐Shan , Yu Jianming , Yu Yisong , Zundel Thomas
Published: March 2011

As an illustration of the frantic development of (meth)acrylic esters anionic polymerization during the last decade, three significant breakthroughs will be presented and analyzed:— extension of the LAP (ligated anionic polymerization) concept to the practical synthesis of both high iso‐ or syndio high MW PMMA;

— the production of “perfect” hydrocarbon gels from tailored PMMA‐polybutadiene‐PMMA triblock copolymers;

— the use of reactivity “boosters” allowing to climb back up the nucleophilic reactivity scale, i.e. initiating styrene, dienes and (meth)acrylates polymerization with alcoholates and silanolates.
Enzymatic ring‐opening polyaddition for chitin synthesis: A cationic mechanism in basic solution?
Authors: Kiyosada Toshitsugu , Shoda Shin‐Ichiro , Kobayashi Shiro
Published: March 2011

The in vitro synthesis of chitin via a nonbiosynthetic path has been achieved for the first time by enzymatic ring‐opening polyaddition of a chitobiose oxazoline monomer (C2O). Chitinase, a hydrolysis enzyme of chitin, recognized and polymerized the monomer regio‐ and stereoselectively. The structure of artificial chitin was confirmed by comparison with an authentic natural chitin sample with the use of CP/MAS 13C NMR and IR spectroscopy. X‐ray diffraction as well as NMR analysis showed its crystal structure of α‐chitin. Characteristic features of the present polymerization are described.
Intra‐ and intermolecular chain transfer to macromolecules with chain scission. The case of cyclic esters
Authors: Penczek Stanislaw , Duda Andrzej , Szymanski Ryszard
Published: March 2011

Chain transfer to macromolecules with chain scission is the most often observed “side” reaction in the polymerization of heterocyclics. In our previous works we analysed quantitatively the intramolecular chain transfer to the own macromolecule (back‐biting). This paper gives a general treatment of the kinetics of polymerization with propagation and intermolecular chain transfer to macromolecules, accompanied with chain scission. The numerical solution developed allows determining the kp/ktr ratio from the dependence of m̄w/m̄n on monomer conversion. This treatment was applied to the polymerization of L,L‐lactide and kp/ktr ratios were measured for covalent alcoholate active species bearing Al, Fe, Ti, Sm, and La. In this way selectivities of active species (expressed with kp/ktr) were for the first time measured and finally correlated with the atomic number of the corresponding metal atoms, related to the strength of the bond involved in the monomer addition.
Alkali metals plus complexants: From alkalides and electrides to aromatic anions
Authors: Dye James L.
Published: March 2011

Electron transfer from an alkali metal to a suitable complexant for the cation can yield crystalline ionic solids that contain the complexed cation and either an alkali metal anion (alkalide) or a trapped electron (electride). The nature and properties of electrides are emphasized in this paper. When the organic complexant contains aromatic groups, the anionic species is an aromatic radical anion. Preliminary work on the addition of alkali metals to LOGEAs (large organic globular electron acceptors) is described and strategies for the synthesis of mixed electride‐anion compounds are considered.
Grafting and initiation reactions
Authors: Rånby Bengt
Published: March 2011

Grafting of acrylic monomers onto cellulose substrates in acid aqueous medium using complex of Mn3+ ions as a redox initiator is described. Assuming that the /Mn3+/ ions react with aldehydes and vicinal diols, the rate of these reactions has been measured spectroscopically. (ESR and visible light) using model compounds. It is concluded that the /Mn3+/ grafting onto cellulose is a radical reaction initiated mainly by oxidation of aldehydes at reducing end groups and C‐C bond scission of vicinal diols at the end groups and along the cellulose chains. The initiation rates of the Ce4+, /Mn3+/ and VO22+ redox ions are related to their oxidation potential.
Intra‐ and intermolecular reactions of nucleophilic carbenes
Authors: Warkentin John
Published: March 2011

General properties of nucleophilic carbenes are addressed briefly. The preparation of oxadiazoline precursors of such carbenes, and some of their chemical reactions, are presented. Intramolecular reactions include rearrangement and attack by the carbene center on a tethered functional group. Intermolecular reactions include nucleophilic attack at the carbonyl carbon of isocyanates and at the triple bond of dimethyl acetylenedicarboxylate.
Catalytic degradation of polyethylene and polypropylene to fuel oil
Authors: Sakata Yusaku
Published: March 2011

Thermal and catalytic degradation of plastic polymers, polyethylene and polypropylene to fuel oil were carried out in batch operations. The catalysts employed were acid silica‐alumina (SA‐1, SA‐2) and zeolite ZSM‐5, and non‐acidic mesoporous silica FSM (folded sheet material). The yields of product gas, liquid and residues, recovery rate of liquid products, and boiling point ranges of liquid products due to degradation were compared with those of non‐catalytic thermal degradation. Both the effect of catalytic contact mode and of catalyst type on the degradation were studied.

In liquid‐phase degradation of PP over SA‐1, liquid hydrocarbon products were obtained in a yield of 69 wt.‐% with a boiling point range 36‐270°C, equivalent to the boiling point of normal paraffins C6 ‐ C15. The liquid products from catalytic degradation have a carbon‐number distribution very similar to commercial motor gasoline. In vapor‐phase contact, the yield of liquid products was much lower (54%) and the rate of liquid recovery was much slower.

With FSM, the initial rate of degradation of PP and PE to liquid products was as fast as that over acid catalyst SA‐1, but the yield of liquid products was higher. The liquid products from catalytic degradation over FSM have a carbon‐number distribution similar to kerosene and diesel oil. In repeated use, SA‐1 deactivated very rapidly due to coke deposition on the catalyst, whereas FSM deactivated much more slowly. These findings suggest that mesopores surrounded by the silica sheet may act as reservoir for radical species, which accelerate the degradation of plastic melt.
New approach to recycling of thermosets
Authors: Kresta J. E. , Xiao H. X. , Suthar B. , Li X. H. , Sun S. P. , Klempner D.
Published: March 2011

The decrosslinking of thermosetting reaction injection molded (RIM) polyurethane‐urea products with the smallest amounts of glycols was studied. The effects of the reaction conditions on the properties of liquid oligomers were determined. Successful scale‐up studies and utilization of the resulting liquid oligomers for preparation of RIM products, coatings and adhesives are described.
Recycling of mixed automotive plastics
Authors: Deanin Rudolph D. , Barry Carol M. , Woramongconchai Somsak , Parikh Sona C.
Published: March 2011

Mixed plastics from junked autos were homogenized by milling or extrusion, modified by addition of low‐molecular‐weight low‐melt‐viscosity polymers, and processed by compression or injection molding. Properties were comparable with high‐density polyethylene and common building panel materials.
Recycled injection‐molded and fibre‐reinforced polyethylene/polypropylene
Authors: Riedl Bernard
Published: March 2011

In this presentation, we are concerned with the fabrication and characterization of samples of compression‐molded and injection‐molded recycled polyethylene, with, in some cases, addition of cellulose fibre. We wish to know what is the performance of such plastics, as compared to the virgin materials and what is the effect of added fibre in both molding modes.
Recycling of polymeric composites
Authors: Mang Thomas , Haulena Friedhelm
Published: March 2011

For material recycling, composites have to be separated into their components, as only non‐mixed raw materials can grant high quality standards. A combined mechanical and subsequent electrostatic separation can be classified as highly economic because it is a dry treatment. This is demonstrated on wire scrap. The separated copper and synthetic materials are obtained in a high degree of purity.

Chemical disaggregation of composites has been worked out with medicinal blister packs and beverage packs. Two methods of separation were used: separating the plastic‐aluminium composite by dissolving the plastic material or dissolving the adhesive that bonds together the plastic and aluminium. To demonstrate the technical feasibility of the processes, a pilot plant with a capacity of up to 25 tons of blister pack material per year was built. Chemical separation with non‐problematic aqueous media was demonstrated with flocked plastics.

When integrating composites into chemical processes, questions concerning material specification as well as preparation and chemical utilization must be answered. Mechanical preparation of appropriate raw materials has been exemplified by mixed packing waste, carpet‐floor waste, and synthetic material from electrical waste. After the raw materials were analyzed and studies of their quantity and compositions were made, their possible re‐use as raw material within a chemical process has been elaborated.