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Poly(vinyl alcohol) grafted with poly(d,l-lactide) or poly(d,l-lactide-co-glycolide) oligomers, were synthesized in our laboratory and investigated with respect to their potential for tissue engineering applications. In order to understand their structure–properties relationships the effect of length and composition as well as number of polyester grafts on PVA backbone chain on water uptake capability and hydrophilicity/hydrophobicity balance and on mechanical properties of hydrogels was evaluated. The E moduli of hydrogels display values between 0.01 and 100 MPa. The results indicate the route for the development of polymers with a very broad range of properties similar to those of natural cartilage tissue. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3682–3688, 2013

The swellability and mass loss of poly(vinyl alcohol)-graft-[poly(rac-lactide)/poly(rac-lactide-co-glycolide)] hydrogels upon hydrolysis are strongly affected by the composition of the hydrogels. Hydrophobic hydrogels remain at a relatively constant mass for a couple of weeks, and the mass decreases dramatically thereafter, whereas more hydrophilic hydrogels lose mass right from the beginning. All hydrogels display water uptake values between 90 and 280% within 8 weeks. For longer periods of degradation, the water uptake increases up to a maximum of about 900%. Studies of the thermal properties of samples upon degradation and their IR measurements have shown that the degradation rate is related to the physical and chemical structure of the hydrogels and hence to the hydrophobic/hydrophilic balance; that is, the degradation increases with the increasing hydrophilicity of the material. As a result, degradation can be engineered through the variation of the composition and structure of the material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The flexible C-terminal region of the anaphylatoxic peptide C3a was reported to contain the receptor binding site. To elucidate the receptor binding conformation of the C-terminus, as well as to examine a synthetic approach to potential C3a-antagonists, 26 cyclic disulfide bridged C3a analogues were synthesized. Solid phase peptide synthesis was performed on different polymeric supports by individual peptide synthesis, with Fmoc strategy, and simultaneous multiple peptide synthesis, using Boc and Fmoc strategies. Both strategies gave open-chain peptides in comparable yields. Syntheses using the Boc strategy employed the HF-labile 4(methoxy)benzyl group (Mob) for beta-thiol protection of cysteine; in contrast, the TFA-stable protecting groups, acetamidomethyl (Acm) and trityl (Trt), were chosen for syntheses employing Fmoc strategy. Ring closure reactions by iodine oxidation were carried out starting from protected (Acm/Acm, Trt/Acm) or unprotected dithiols. The resulting cyclic C3a analogues were characterized by HPLC, amino acid analysis, and FAB-MS. Conformational investigations using CD spectroscopy and theoretical structural investigations by means of molecular dynamics calculations revealed that slight variations in sequence result in pronounced conformational consequences. The potential of cyclic C3a analogues to activate or to desensitize guinea pig platelets, a standard test system for biological activities of anaphylatoxic peptides like C3a, revealed relatively low activities for cyclic peptides (< 0.1% C3a activity). N-terminal acylation with cationic, arginine-rich sequences like YRRGR- led to amplified biological effects. Three of the synthesized peptides, namely CAALCLAR (P1), YRRGRCGGLCLAR (P5) and YRRGRAhxCGGLCLAR (P8), point in the direction of C3a antagonists.

Within the scope of structure-function studies on the proteohormone insulin, the role of the C-terminal segment B26-B30 for self-association and receptor interaction was analyzed. Insulin derivatives with modifications in the region B26-B30 were synthesized by trypsin-catalyzed coupling reactions of des-(B23-B30)-insulin with synthetic peptides. The peptides were obtained by Fmoc solid-phase peptide synthesis. Insulins with multiple amino acid-->glycine substitutions were examined to distinguish between the influence of the side chains and the influence of the main chain in positions B27-B30 on the self-association of the hormone. The analogues [GlyB27,B28,B29,B30]insulin and [GlyB27,B28,B30]insulin exhibit relative receptor affinities of 80% and self-associate. The successive extension of [AlaB26]des-(B27-B30)-insulin-B26-amide (relative receptor binding 273%) with amino acids corresponding to the native sequence B27-B30 showed the influence of the length of the B-chain on receptor affinity: the extension by B27-threonine amide reduces receptor binding to 71%, all further prolongations have only small effects on the binding. The effect of the B28-side chain on main-chain conformation, self-association and receptor binding was examined with [XB28]des-(B29-B30)-insulin-B28-amides (X = Phe, Gly, D-Pro). While the glycine and D-proline analogues (relative binding 104 and 143%, respectively) retain the self-association properties typical of insulin, [PheB28]des-(B29-B30)-insulin-B28-amide (relative binding 50%) shows diminished self-association. The backbone-modified insulin derivative [SarB26]des-(B27-B30)-insulin-B26-amide (sarcosine = N-methylglycine) exhibits an unexpectedly high receptor affinity of 1100% which demonstrates that the B26-amide hydrogen of the native hormone is not important for receptor binding.

1,6-Bis-O-phenoxycarbonyl-2,3∶4,5-di-O-isopropylidenegalactitol (5) and 1,6-di-O-phenoxycarbonylgalactitol (6) were prepared from galactaric acid in four and five steps, with overall yields of 76% and 72%, respectively. These AA type monomers were reacted with α,ω-diamines (H2N–(CH2)x–NH2; x = 2–10 and 12) as BB type monomers in a polycondensation reaction to result in polyurethanes with four protected hydroxy groups PiG2-12 or polyurethanes with four free hydroxy groups PG2-6 per repeating unit. The polyurethanes of the PiG-series were transformed by hydrolysis into polyurethanes with four free hydroxy groups per repeating unit PaG2-6. As shown by 1H NMR spectroscopy, the polyurethanes of the PG series and of the PaG series differ in their microstructure: the polymers of the first series has urethane groups with primary and secondary carbon atoms adjacent to the urethane group, while the polymers of the second series have only primary carbon atoms adjacent to the urethane group. The molecular weights of the polyurethanes, as determined by means of gel permeation chromatography in dimethylacetamide–LiCl, are in the range of 15000 to 63000 for the PiG and the PaG series and 15000 to 36000 for the PG-series with polydispersity indices of about 1.6. The thermal stability of the polyurethanes was studied by means of TGA, the polyurethanes with protected hydroxyl groups being more stable than those with free hydroxy groups. The polyurethanes of the PiG series are semi-crystalline materials with melting points between 160 and 167 °C and glass transition temperatures between 59 and 78 °C. The polyurethanes of the PG and the PaG series show glass transition temperatures of 44 to 74 °C; no melting transition is observed before decomposition starts at about 180 °C.

The bis(ethylene carbonate) monomers 3,4-O-isopropylidene-D-mannitol-1,2:5,6-dicarbonate (2) and D-mannitol-1,2:5,6-dicarbonate (1) were prepared fromD-mannitol in yields of 81 and 74%, respectively. These AA-type monomers were reacted with α, ω-diamines (H2N—(CH2) x –NH2; x = 2–10 and 12) as BB-type monomers in the sense of a polycondensation reaction. The molecular weights of the polyurethanes with pendant hydroxy groups obtained were determined by means of gel permeation chromatography in dimethylacetamide/LiCl and are in the range of 20 × 103 to 87 × 103 with polydispersity indices of ca. 1.6. The polyurethanes show primary and secondary hydroxy groups with a ratio of ca. 15:85. This is a consequence of the different direction of opening of the substituted ethylene carbonate ring which results in structurally isomeric repeating units. The polyurethanes obtained from 2 and diamines with two free hydroxy groups and two protected hydroxy groups in the repeating unit are semicrystalline materials with mel...

Mono- and bifunctional poly(phenylene oxide) (PPO) macroinitiators for atom transfer radical polymerization (ATRP) were prepared by esterification of mono- and bishydroxy telechelic PPO with 2-bromoisobutyryl bromide. The macroinitiators were used for ATRP of styrene to give block copolymers with PPO and polystyrene (PS) segments, namely PPO-block-PS and PS-block-PPO-block-PS. Various ligands were studied in combination with CuBr as ATRP catalysts. Kinetic investigations revealed controlled polymerization processes for certain ligands and temperature ranges. Thermal analysis of the block copolymers by means of DSC revealed only one glass transition temperature as a result of the compatibility of the PS and PPO chain segments and the formation of a single phase; this glass transition temperature can be adjusted over a wide temperature range (ca 100–199 °C), depending on the composition of the block copolymer. Copyright © 2005 Society of Chemical Industry

Lipase-catalyzed ring-opening bulk polymerizations of 6(S)-methyl-morpholine-2,5-dione (MMD) were investigated. Selected commercial lipases were screened as catalysts for MMD polymerization at 100 C. Polymerizations catalyzed with 10 wt % porcine pancreatic lipase type II crude (PPL), lipase from Pseudomonas cepacia, and lipase type VII from Candida rugosa resulted in MMD conversions of about 75% in 3 days and in molecular weights ranging from 8200 to 12,100. Poly(6-methyl-morpholine-2,5-dione) [poly(MMD)] had a carboxylic acid group at one end and a hydroxyl group at the other end. However, lipase from Mucor javanicus showed lower catalytic activity for the polymerization. During the polymerization, racemization of the lactate residue took place. PPL was selected for further studies. The rate of polymerization increased with increasing PPL concentration under otherwise identical conditions. When the PPL concentration was 5 or 10 wt % with respect to MMD, a conversion of about 70% was reached after 6 days or 1 day, respectively, whereas for a PPL concentration of 1 wt %, the conversion was less than 20% even after 6 days. High concentrations of PPL (10 wt %) resulted in high number-average molecular weights (

Summary: Random copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and allyl methacrylate (AMA) were prepared via atom transfer radical polymerization (ATRP). AMA is a bifunctional monomer with two double bonds of different reactivity: a highly reactive methacrylate double bond and an allyl ester double bond of lower reactivity. In order to obtain linear polymers with pendant allyl ester groups, the copolymerization conditions have to be optimized with respect to the concentration of AMA, the catalyst system applied – especially the ligand – and the temperature. By means of kinetic studies the reaction parameters for a controlled polymerization were determined. The results obtained show that the higher the temperature and the amount of AMA is the higher is the probability of irregular chain growth and side reactions induced by the pendant allyl ester groups such as hydrogen abstraction from the allyl position or radical addition to the allyl ester double bond. The random copolymers were photochemically crosslinked by using 2,2-dimethoxy-2-phenylacetophenone as photoinitiator. The thermal properties of linear and crosslinked polymers were determined. The glass transition temperatures of both show no significant difference at low AMA content and thus low crosslinking densities. GPC eluograms of MMA/BMA (70:30) copolymers with 5 mol-% AMA at different conversions.

Poly(allyl methacrylate) (PAMA) and random copolymers of styrene (St) with allyl methacrylate (AMA) were prepared via atom transfer radical polymerization. For the homopolymerization of AMA, the maximum conversion depends on the reaction conditions and on the monomer/initiator ratio. For the copolymerization, AMA conversions of up to 90% were obtained while no cross-linking occurred. Kinetic studies of the homopolymerization revealed a controlled polymerization up to a certain conversion whereas at higher conversions, multimodal molecular weight distributions caused by branching reactions and cross-linking were observed. The copolymerization of AMA with St allowed a controlled reaction up to conversions higher than 90%. The copolymers obtained were soluble in standard organic solvents. In a subsequent reaction, these copolymers were cross-linked both thermally and photochemically using suitable initiators. Moreover, pendant double bonds were brominated quantitatively.

Tetramethylene urea (TeU) is successfully copolymerized with γ-butyrolactone (γBL), leading to an alternating poly(amide urethane) with alternating carbonyl-amino-tetramethylene-amino and carbonyl-trimethylene-oxy repeating units (Mn = 12 600; Mw = 21 100; Mn = 1.67) and with a Tm of 196.5 °C and a Tg of 36.4 °C. Small defects in the microstructure of the alternating poly(amide urethane) arise from the formation of TeU−TeU diads. Furthermore, TeU is successfully copolymerized with mixtures of γBL and ethylene carbonate (EC) or 1,2-propylene carbonate (PC). From NMR spectroscopic data of the terpolymers obtained, it is concluded that the reactivity of the five-membered cycles used increases in the following order: EC ≫ PC ≈ γBL. It is possible to increase the content of γBL repeating units in the poly[(TeU−γBL)-stat-(TeU−EC)] or poly[(TeU−γBL)-stat-(TeU−PC)] by increasing the fraction of γBL in the feed. 13C NMR spectroscopy reveals that TeU−EC or TeU−PC and TeU−γBL units are randomly distributed in th...

The ring-opening polymerization (ROP) of the cyclic ester amide (cEA) 5 (systematic name, l-oxa-8-aza-cyclotetradecane-9,14-dione)- prepared from adipic anhydride and 1-amino-6-hexanol - in the melt at 165 °C and in solution at 100 °C and 120 °C with Bu 2 Sn(OMe) 2 or Ti(OBu) 4 as initiator yields the alternating poly(ester amide) (PEA) 4 (systematic name, poly(5-(6-oxyhexylcarbamoyl)-pentanoate) with regular microstructure. Kinetic studies for different monomer-to-initiator ratios, different reaction media, initiators and temperatures reveal that the ROP is a first-order reaction with respect to the monomer. Under suitable polymerization conditions termination and transfer reactions are suppressed. The elementary chain growth reaction proceeds by a coordination insertion mechanism in analogy to the polymerization of lactones. By using monohydroxy- and bishydroxy-functional telechelic poly(ethylene oxide) and Sn(octoate) 2 as the initiating system poly(ethylene oxide)-block-poly(ester amide)s and poly(ester amide)-block-poly(ethylene oxide)-block-poly(ester amide)s are obtained. The poly(ester amide) 4 is a semicrystalline material with a melting point of 140 °C, the block copolymers are phase separated systems showing two melting points characteristic for the respective homopolymers.

Poly(amide urethane)s were prepared from e-caprolactam, amino alcohols, and diphenyl carbonate or ethylene carbonate in three steps. Polycondensation was performed either with α-hydroxy-ω-O-phenyl urethanes or with α-hydroxy-ω-O-hydroxyethyl urethanes; it was found that the reactivity at 90 °C of the first is much higher than that of the latter. For nearly equal reactivity, the temperature for the polycondensation of α-hydroxy-ω-O-hydroxyethyl urethanes had to be increased from 90 °C to 150 °C. The microstructure of the resulting poly(amide urethane)s differs by the content of urea groups in the polymer chains, which is 5% for poly(amide urethane)s prepared from α-hydroxy-ω-O-phenyl urethanes and 15% for poly(amide urethane)s prepared from α-hydroxy-ω-O-hydroxyethyl urethanes. As a consequence, the thermal properties of the poly(amide urethane)s differ slightly.

Alternating poly(amide urethane)s from e-caprolactam, amino alcohols H2N–(CH2)x–OH (x=2–6), and diphenyl carbonate were prepared by polycondensation of α-hydroxy-ω-O-phenylurethanes 4a-e. The degree of oligomerization was adjusted by the conversion. Oligomers with two or three O-phenylurethane end groups and predetermined molecular weight were prepared by polycondensation of the α-hydroxy-ω-O-phenylurethanes 4a-e in the presence of comonomers with O-phenylurethane end groups in a given concentration. In order to prepare oligomers with hydroxyl and carboxyl groups at both chain ends suitable for coupling reactions, chain analogous reactions were performed with amino acids and amino alcohols. The microstructure of the polymers and the nature of end groups was determined by means of 1H NMR spectroscopy and the molecular weights were determined by means of gel permeation chromatography. The poly(amide urethane)s 5a-e prepared are semicrystalline materials with melting points between 150 and 200 °C.

Die Dauerhaftigkeit glasfaserbewehrter Betonbauteile wird wesentlich durch die Zusammensetzung der Zementsteinmatrix, die Art des Glases und dessen Oberflachenbeschaffenheit einschlieslich erforderlicher Beschichtungen bestimmt. Im Beitrag wird anhand experimenteller Ergebnisse eine Ubersicht zu den einzelnen Einflussen und deren Zusammenwirken im Materialverbund gegeben. Concrete Technology and Durability of Glass Fibre Reinforced Structures The durability of glass fibre reinforced concrete structures is significantly determined by matrix composition, the type of glass and its surface quality including necessary coatings. In the paper an experimental overview is given concerning special material influences and their interaction in the composite.

Tetramethylene urea (TeU, 1) is successfully copolymerized with 1,2-propylene carbonate (PC, 2), leading to a polyurethane (M n = 12 200; M w 18 400; M w /M n = 1.50) with T m of 145.7°C and a T g of 53.7°C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate. Hence, a well-underlined mechanims for the copolymerized is proposed. Furthermore, TeU, is successfully copolymerized with mixtures of PC and ethylene carbonate (EC, 3). From NMR spectroscopic data of the polyurethanes obtained, it is concluded that PC is less reactive than EC. However, it is possible to increase the PC content in poly(TeU-EC-stat-TeU-PC) by increasing the PC/EC ratio in the feed. 13 C NMR spectroscopy reveals that a random copolymer is obtained. This conclusion is supported by differential scanning calorimetry (DSC) data, which show a continuous decrease in T m with increasing PC content.

Im Rahmen der vorliegenden Arbeit wurde die CVD-Polymerisation von aminosubstituiertem [2,2]-Paracyclophan zur Polymerbeschichtung und gleichzeitigen Funktionalisierung von Titan-Oberflachen durchgefuhrt. Parallel erfolgte die Funktionalisierung mittels Silanisierung mit 3-Aminopropyl-triethoxysilan. Die generierten Aminogruppen wurden zur kovalenten Immobilisierung von bioaktiven Substanzen genutzt, um die Adhasion von Knochenzellen zu fordern und deren Wachstum zu stimulieren. Als bioaktive Substanzen wurden das Pentapepid GRGDS und der Wachstumsfaktor BMP-2 ausgewahlt. Die kovalente Bindung wurde mit dem Kopplungsreagenz Hexamethylendiisocyanat durchgefuhrt. Zur Charakterisierung der einzelnen Modifizierungsschritte wurden die Rontgenphotoelektronenspektroskopie, die Rasterkraftmikroskopie und die Kontaktwinkelmessung eingesetzt. Der Nachweis der kovalenten Bindung der bioaktiven Substanzen erfolgte mittels radioaktiver Markierung bzw. Surface-MALDI-ToF-MS. In vitro-Biokompatibilitatstests mit primaren, humanen Osteoblasten zeigten die Verbesserung der Zelladhasion und des Spreadings auf den bioaktiv ausgerusteten Titanoberflachen. Surface Modification of Titanium for Improvement of the Interfacial Biocompatibility We report the CVD-polymerisation of amino-functionalized [2,2]-paracyclophane for polymer coating and functionalization of titanium surfaces. Additionally, the functionalization was carried out by silanization with 3-aminopropyl-triethoxysilane. The generated amino-groups were used for covalent immobilization of bioactive substances to stimulate the adhesion and growth of osteoblasts. As bioactive substances the pentapeptide GRGDS and the growth factor BMP-2 were chosen. The covalent bonding was achieved by activation with hexamethylene diisocyanate. Each modification step was characterized by X-ray-photoelectron-spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements. The covalent bonding of the bioactive substances was proven by radiolabelling and surface-MALDI-ToF-MS. In vitro-biocompatibility tests with primary, human osteoblasts demonstrated the improved cell adhesion and spreading on the bioactive modified titanium surfaces.

Phenoxycarbonyloxymethyl ethylene carbonate 4 was synthesized from glycerol carbonate and phenyl chloroformate Polyurethanes with pendant hydroxyl greups were obtained from polycondensation reactions of this AA* monomer with diamines. These polymers contan primary as well as secondary hydroxyl groups The obtained polyurethanes are amorphous materials. The glass transition temperature decreases with increasing number of methylene groups between the urethane groups.

Bis(hydroxy)telechic bisphenol A polycarbonate (PC) was prepared via melt polycondensation of bisphenol A (BPA) and diphenyl carbonate (DPC) using lanthanum(m) acetylacetonate as a catalyst for transesterification. Subsequently, the polycarbonate was converted to a bifunctional macroinitiator for atom transfer radical polymerization (ATRP) with the reagent, α-chlorophenylacetyl chloride. The macroinitiator was used for the polymerization of styrene (S) and methyl methacrylate (MMA) to give PS-block-PS and PMMA-block-PC-block-PMMA triblock copolymers. These block copolymers were characterized by NMR and GPC. When styrene and methyl methacrylate were used in large excess, significant shifts toward high molecular weights were observed with quantitative consumption of the macroinitiator. Several ligands were studied in combination with CuCl as the ATRP catalyst. Kinetic studies reveal the controlled nature of the polymerization reaction for all the ligands used.

Alternating poly(ester amide)s 6a-e from succinic anhydride and α,ω-amino alcohols H 2 N-(CH 2 ) x -OH (x = 2-6) 2a-e were obtained in two steps: α-carboxyl-ω-hydroxy amides 3a-e were prepared from the starting materials in a highly selective reaction, followed by a polycondensation reaction. 1 H and 13 C NMR analyses of the poly(ester amide) s clearly reveal the alternating microstructure. The poly(ester amide)s with homologous α,ω-amino alcohols H 2 N-(CH 2 ) x -OH (x = 2-6) are semicrystalline materials, their melting points show the odd/even effect observed for [n]-polyamides and [n]-polyurethanes. Heating the poly(ester amide)s 6a-e yields the corresponding N-(hydroxyalkyl) imides 4a-e with no trace of cyclic ester amides. Theoretical calculations revealed that the cyclic ester amides 5a-e are clearly richer in energy than the isomeric N-(hydroxyalkyl) imides. These results show that cyclic ester amides can not be prepared from N-(hydroxyalkyl) imides by ring-enlargement reactions.

The ring-opening polymerization of the cyclic ester amide (cEA, 2) (systematic name, 1-oxa-7-aza-cyclotridecane-8,13-dione)prepared from adipic anhydride and 1-amino-5-pentanolin the melt at temperatures above 145 °C with Bu2Sn(OMe)2, Ti(OBu)4, Al(O-sec-Bu)3, or Sn(octoate)2 as initiator yields the poly(ester amide) (PEA, 3) (systematic name, poly(5-(5-oxypentylcarbamoyl)pentanoate) with regular microstructure. This poly(ester amide) is a semicrystalline material with a melting point of 108 °C. The elementary chain growth reaction proceeds by a coordination insertion mechanism in analogy to the polymerization of lactones. The monomer-to-initiator ratio and the conversion determine the number-average molecular weight. By using hydroxy telechelic poly(ethylene oxide) with Sn(octoate)2 as initiator poly(ester amide)-block-poly(ethylene oxide) and poly(ester amide)-block-poly(ethylene oxide)-block-poly(ester amide) were obtained. Kinetic studies for different monomer-to-initiator ratios, different temperature...

Poly(esters amide)s from adipic anhydride and α, ω-amino alcohols were obtained by polycondensation of α-carboxyl-ω-hydroxyl amides under mild conditions in solution or by bulk polycondensation at elevated temperatures. For the polycondensation in bulk the influence of catalyst and of temperature on the number-average molecular weight was studied. At a temperature of 170 °C the poly-condensation process is followed by a ring-closing depolymerisation and the formation of cyclic ester amides. Ten- to fourteen-membered cyclic ester amides were obtained and characterized. The ring-opening polymerisation of these cyclic ester amides leads, in a controlled mode, to poly(ester amide)s. The interconversion of poly(ester amide)s and cyclic ester amides by ring-closing depolymerisation and ring-opening polymerisation is possible. The poly(ester amide)s from adipic anhydride and homologous α, ω-amino alcohols H 2 N-(CH 2 ) x -OH (x = 2-6) are semicrystalline materials, their melting points show the odd/even effect observed for [n]-polyamides and [n]-polyurethanes.

Density functional calculations were carried out on the B3LYP level of theory to study the initiation and propagation steps of polymerization of methyl vinyl ether (MVE) using [Me2C(Cp)2Zr(Me)]+ an...

Biodegradable ABA triblock copolymers with poly(ethylene oxide) and poly(glycolic acid-valine) blocks were synthesized via ring-opening polymerization of cyclo(glycolic acid-valine) using Ca-alcoholates of hydroxytelechelic PEO as the initiator. The L-valine residue racemized during copolymerization of cyclo(glycolic acid-valine). The crystallization of the block copolymers decreases with decreasing PEO content in the triblock copolymers and with increasing length of the poly(glycolic acid-valine) block. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2916–2919, 2002

Density functional (DFT) calculations were carried out on the B3LYP level of theory on bridged and unbridged cationic zirconocene complexes to clarify why unbridged [Zr(Cp)2(Me)(thf)][BPh4] is not active in the polymerization of methyl methacrylate (MMA), whereas [Zr{(Cp)2CMe2}(Me)(thf)][BPh4] polymerizes MMA readily, as we showed experimentally. It is shown, that the initial step of the polymerizationthe transfer of the metallocene bound methyl group to the first MMA moleculeis endothermic for [Zr(Cp)2(Me)(MMA)]+ but exothermic for [Zr{(Cp)2CMe2}(Me)(MMA)]+. Furthermoreand more importantthe activation energy is higher for the reaction of the unbridged compound compared to the activation energy of the bridged compound. From these results and an estimation of the rate constants it follows that in the temperature range investigated experimentally (−30 to +30 °C) either the endothermic product is not formed at all and/or the reversed reaction to the reactant is much faster than the reaction with the next MMA...

Surfaces covered with polyethylene glycol (PEG) have been shown to be biocompatible because PEG yields nonimmunogenicity, nonantigenicity and protein rejection. To produce a biocompatible surface coating, we have developed a method for grafting PEG onto modified poly(vinylidene fluoride) (PVDF) films. The first step was to create carboxy groups on the PVDF surface following covalente coupling of polyethylenimine (PEI) to achieve high density of amino groups. These surface amines were reacted with formyl-terminated PEG's with various molecular weight. The modified PVDF surface was characterized by means of static contact angle measurements, infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The influence of the chain length on lysozyme repellence was investigated by means of surface-MALDI-Tof mass spectrometry (Surface-MALDI-Tof-MS). Lysozyme adsorption was significantly suppressed on the PEG 5000 modified PVDF surface.

Monofunctional poly(ethylene oxide) macroinitiators with a molecular weight of 2000, 5000, 10 000, 20 000 and bifunctional poly(ethylene oxide) macroinitiators with a molecular weight of 20 000 were used for the atom transfer radical polymerisation (ATRP) of hydroxyethyl methacrylate (HEMA) in ethylene glycol as a solvent. The polymerisation proceeds in a controlled way up to high conversions. The molecular weight of the obtained copolymers increases linearly with conversion. A high rate of polymerisation was observed for the ATRP of HEMA. The effect of the poly(ethylene oxide) moiety on the course of the reaction is limited to solvating effects. The surface analysis of poly(ethylene oxide)/poly(hydroxyethyl methacrylate) block copolymers by means of atomic force microscopy in tapping mode using phase imaging shows phase separated domains with characteristic features related to the volume fraction of the respective blocks.

Full Paper: Chemical modification of recombinant hirudin (r-hirudin) is necessary whenever surface-confinement to a biomaterial or biotinylation for subsequent conjugation with carriers is intended. Here, we report a modification strategy that permits chemical discrimination between r-hirudin's amino groups and preserves its thrombin inhibitor activity. By reaction with Msc-ONSu, protective groups were successively introduced in r-hirudin yielding four derivatives (Msc) x -hirudin (1 ≤ x ≤ 4) and pure fractions were isolated by ion exchange chromatography. Structure-function relationships were studied for all derivatives and revealed a decrease in activity of more than 90% as compared to unprotected r-hirduin. MALDI-TOF MS was used to determine the locations of the Msc groups. Furthermore, evidence was provided that r-hirudin's N-terminal amino group is highly important for its anti-thrombin activity. Selective modification of the lysine residues which maintained the free N-terminal amino group preserved the anti-thrombin activity of r-hirudin even after biotinylation and subsequent linkage to streptavidin or confinement to a polymer surface. Anti-thrombin activity of r-hirudin derivatives and r-hirudin as determined by amidolytic assay. Low extinction expresses high anti-thrombin activity of the r-hirudin derivatives.

Low-temperature plasma technologyboth glow discharge under reduced pressure as well as barrier discharge under normal pressureare well established in different industrial applications. Since recently, however, the plasma technology is being introduced in textile industry as well. Fields of application are desizing, functionalizing, and design of surface properties of textile fibers. Plasma technology is suitable to modify the chemical structure as well as the topography of the surface of the material. Examples of natural as well as man-made fibers prove the enormous potential of plasma treatment of textile materials. It has proven to be successful in shrink-resist treatment of wool with a simultaneously positive effect on the dyeing and printing. Not only the chemical structure of the surface is modified using different plasma gases but also the topography of the surface. A highly hydrophobic surface with a particular surface topography in contact with water is extremely dust- and dirt-repellent and hence should be also repellent to bacteria and fungi. Man-made fibers to be used under chemical stress are modified with diffusion-barrier layers on their surfaces without modifying the bulk properties; hence, the stability of those fibers is significantly improved.

Monofunctional PEO-macroinitiators (mPEO-F) were prepared from monohydroxyfunctional poly(ethylene oxide)s and 2-chloro-2-phenylacetylchloride. In order to synthesise poly(ethylene oxide)-block-poly(styrene) (PEO-b-PS) the macroinitiators were applied to the atom transfer radical polymerisation (ATRP) of styrene in the bulk. Well-defined block copolymers were obtained with predetermined molecular weight and narrow molecular weight distribution. Kinetic aspects of ATRP of styrene depending on the molecular weight of the macroinitiator are discussed. Surface analysis by means of atomic force microscopy in tapping mode using phase imaging reveals characteristic morphologies as a function of the volume fraction of PEO. The higher the PEO content the more PEO is found at the polymer/air interface. The preparation of the samples has a main impact on the observed morphology. The polymer films are hygroscopic and alter their morphology being exposed to air.

The polymerization of 1-hexene with the catalyst systems Cp 2 ZrCl 2 /MAO and Me 2 SiInd 2 ZrCl 2 /MAO is investigated in order to elucidate the nature of the active species in zieconocene/MAO catalyzed polymerizations. Varying monomer concentration and monomer conversion does not result in any unexpected behavior. However, changing catalyst and cocatalyst concentration leads to broadened, or even bimodal, molecular weight distributions under certain reaction conditions. These results may be interpreted in terms of a coexistence of two active species with different rates of propagation and of termination.

Ring-opening polymerisation is a mean to transform stepwise polymerisation reactions into chain reactions, the cyclic monomers being prepared by intramolecular condensation of open chain bifunctional monomers [1,2]. The ring-opening polymerisation is initiated most conveniently with ionic initiators which may be of macromolecular structure. Thus, block- -and graft copolymers are obtained. To synthesize well-defined architectures the elementary reactions of the ring-opening polymerisation have to be known in detail since there are various unusual features. Six-membered cyclic carbonates, in particular 2,2-dimethyltrimethylene carbonate (DTC), are polymerised anionically and the copolymerisation of different cyclic carbonates results in random copolymers [3-14]. The copolymerisation of cyclic carbonates with e-caprolactone (ECL) yields block copolymers with a tapered structure between the two blocks showing a compositional gradient from DTC-rich to ECL-rich segments [6,10,15,16]. While in both cases the active species is an alcoholate, the active species in the anionic ring-opening polymerisation of pivalolactone (PVL) is a carboxylate; thus, copolymerisation with DTC yields block copolymers since the carboxylate once formed is unable to attack the cyclic carbonate [16,17].

The efficiency of the proteolytic enzyme papain in conferring shrink-resistance to wool tops and woven fabrics has been enhanced by pretreatment of the wool with lipase/sodium monoperoxyphthalate/sodium sulphite. This process may be considered as a zero-AOX shrink-proofing treatment. The wool samples treated with this system show excellent shrink-proofed properties. Infrared spectroscopy and X-ray photoelectron spectroscopy showed that the Bunte salt together with low concentrations of cystine monoxide and cystine dioxide are formed in the course of the reaction. Studies of the surface of the treated wool using scanning electron microscopy have shown the complete absence of wool scales. A mechanism is proposed for shrink resistance in the lipase/sodium monoperoxyphthalate/papain treatment.

The copolymerization of 5-[(4-fluorophenyl)sulfonyl]-2-fluorobenzoic acid with bis(4-hydroxyphenyl)sulfone in 1,1-dioxothiolane with sodium carbonate as a base results in carboxylated poly(ether sulfone)s. The polycondensation polymerization, however, is associated with partial decarboxylation. Conversely, the copolymerization of 2,5-dihydroxybenzoic acid (hydroquinone carboxylic acid) with bis(4-fluorophenyl)sulfone under identical conditions results in a poly(ether ether sulfone) with quantitative decarboxylation.

The ring-opening polymerization of dimethylene urethane (3) (systematic name: 2-oxo-1,3-oxazolidine) with methyl trifluoromethane sulfonate as the initiator is inefficient. It was shown that equimolar amounts of dimethylene urethane and trifluoromethane sulfonate result in the expected active species - 2-methoxy-4,5-dihydro-1,3-oxazolium trifluoromethane sulfonate (5a) -: propagation, however, does not occur. Poly(dimethylene urethane) (4), was obtained by means of polycondensation of a linear monomer, i.e., 2-(2-phenoxycarbonylimino-1-ethoxycarbonylimino)-ethanol (9). This [3]-polyurethane is a semicrystalline material with a melting point of 200.7 °C. Heating above its melting point leads to dimethylene urethane by ring-closing depolymerization. The thermodynamical data support the experimental results with respect to the polymerization / depolymerization equilibrium.

In an adiabatic vacuum calorimeter thetemperature dependence of the heat capacity C p 0 of crystalline 2-methyltrimethylene urethane (MTU; systematic name: 5-methylperhydro-1,3-oxazin-2-one) and of amorphous poly(2-methyltrimethylene urethane) 5PMTU; systematic name: poly(5-methyl-2-oxo-1-oxa-3-azahexamethylene)] was studied between 6 and 335 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shiled the energies of combustion ΔU comb of the monomer and of the polymer were measured. From the experimental data the thermodynamic functions C p 0 (T), H 0 (T)-H 0 (0), S 0 (T), G 0 (T)-H°(0) were calculated in the range of 0 to 340 K, and enthalpies of combustion ΔH 0 comb and thermodynamic parameters of formation ΔH t 0 , ΔS t 0 , ΔG t 0 of the substances studied were estimated at T = 298.15 K and standard pressure. The configurational entropy S 0 conf of the polymer was estimated. The results were used to calculate the thermodynamic characteristics of MTU polymerization in bulk (ΔH 0 pol , ΔS 0 pol , ΔG 0 pol ) with ring-opening and formation of linear PMTU in the range of 0 to 340 K.

Surface modification techniques were employed in order to provide functionalized silicone rubber with enhanced cytocompatibility. Acrylic acid (AAc), methacrylic acid (MAAc) and glycidylmethacrylate (GMA) were graft-co-polymerized onto the surface of silicone induced by an argon plasma and thermal initiation. The polymerizations were carried out in solution, in the case of acrylic acid a vapor phase graft-co-polymerization subsequent to argon plasma activation was carried out as well. Human fibronectin (hFn), which acts as a cell adhesion mediator for fibroblasts, was immobilized by making use of the generated carboxylic or epoxy groups, respectively. Surface analysis was accomplished by means of X-ray photoelectron spectroscopy (XPS), infrared spectroscopy in attenuated total reflection mode (IR-ATR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic contact angle measurements using the Wilhelmy-plate method. The amount of immobilized active hFn was semiquantified by enzyme-linked immunosorbent assay (ELISA) using a structure-specific antibody against the cell-binding domain of hFn. In vitro testing showed a remarkable difference between surfaces exposing adsorbed-only and surfaces with covalently immobilized hFn. © 2001 Kluwer Academic Publishers

Surface immobilization of the thrombin inhibitor r-hirudin was carried out on two different polymers. Linkage to poly(urethane-graft-acrylic acid) (PAC/PU) was done via carboxylic acid groups, using a water soluble carbodimide, while the immobilization on a modified poly[(ethene-co-vinyl acetate)-graft-vinyl chloride] (PVC/EVA) was achieved via the alcohol groups of the polymer using HDI as spacer. Direct immobilization of r-hirudin leaded to a remarkable loss of thrombin activity. As proved by means of protein chemical analysis, loss of activity was due to a selective coupling via the N-terminal amino group of r-hirudin, which is essential for its thrombin activity. Based on these results we developed an immobilization method via an e-amino group of r-hirudin preserving full biological activity of the r-hirudin coated surface. © 2001 Kluwer Academic Publishers

Full Paper: Four different types of polydepsipeptide-polyether block copolymers were synthesized via ring-opening polymerization of 3(S)-sec-butylmorpholine-2,5-dione (BMD) in the presence of hydroxytelechelic poly-(ethylene oxide) (PEO) with stannous octoate as a catalyst. The polymers were an AB block copolymer, an ABA block copolymer, an (A) 2 B star shaped copolymer and an (A) 2 B(A) 2 copolymer, where A is a poly[3(S)-sec-butyl-morpholine-2,5-dione] (PBMD) and B a poly(ethylene oxide) block. The molar ratio of BMD to PEO was varied to obtain copolymers with different weight fractions of PBMD blocks ranging from 59.8 to 96.7 wt.-%, The crystallinity of the PEO phase in the copolymers decreases in the following order: AB > (A) 2 B > ABA > (A) 2 B(A) 2 . The static contact angle θ decreases with increasing PEO content in the block copolymers.

The cationic ring-opening polymerization of tetramethylene urethane (TeU; systematic name, hexahydro-1,3-oxazepin-2-one, (1)) in the melt at 67 °C with methyl trifluoromethanesulfonate (TfOMe) as the initiator yields poly(tetramethylene urethane) (poly(TeU), (6)) with a regular microstructure. This [5]-polyurethane is a semicrystalline material with a Tg of 47 °C and a Tm of 209.5 °C. The reaction proceeds via an active chain end mechanism with a protonated cyclic endo iminocarbonate as the active species. The propagation step involves nucleophilic attack of the carbonyl oxygen of the monomer at the endocyclic methylene group adjacent to the oxygen atom of the active species. The propagation rate constant was 4.2 × 10-4 L·mol-1·s-1. The polymerization of tetramethylene urethane is accompanied by termination reactions; however, transfer reactions and backbiting reactions were not observed. Thermodynamic data support the ring-opening mechanism and the thermal stability (lack of ring-closing depolymerization...

We report the stereospecific polymerization of methyl methacrylate (MMA) with single-component cationic zirconocene catalysts. The complexes Me2CCpIndZrMe(thf)+BPh4- (1) and Me2CCp2ZrMe(thf)+BPh4- (2) are active catalysts for the polymerization of MMA, in remarkable contrast to other cationic zirconocenes. While 1 yields highly isotactic poly(methyl methacrylate) (PMMA), 2 is syndiospecific at low temperatures. This is the first example for a rational control of PMMA microstructure via catalyst symmetry. Polymerization kinetics and stereospecificity control in MMA polymerization with 1 and 2 are discussed. On the basis of the experimental data, a possible polymerization mechanism is proposed.

The neuropeptides vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and substance P (SP) as well as insulin and insulin-like growth factor 1 (IGF-1) were labeled with biotin, fluorescent dyes, and radioactivity to characterize the expression of peptide receptor of a novel cancer cell line, established from a human glioblastoma multiforme. Thus, not only binding sites could be detected but advantages and disadvantages of the different labels could be compared, too. With all three markers, the presence or absence of the receptors could be answered rapidly and sensitively. The glioblastoma cells express receptors for VIP (IC 50 = 9 nM ± 30%), insulin ( K d = 0.66 nM ± 14%, B max = 0.028 nM ± 13%), and IGF-1 ( K d = 21 nM ± 25%, B max = 1.65 nM ± 24%), but there are no binding sites for NPY and SP. As especially VIP and IGF-1 receptors are expressed in huge amounts, these receptors might be an interesting target for tumor diagnostics and therapy.

Aliphatic [n]-polyurethanes were obtained by catalytic polycondensation of suitable α-hydroxy-ω-O-phenyl urethanes (III). 1H and 13C NMR analyses of the resulting [n]-polyurethanes (3 a–g) show a uniform microstructure consisting of urethane groups only, and with carbonate and urea groups being absent. The [n]-polyurethanes with linear alkylidene moieties (3 a–e) are highly crystalline materials, their melting points show the same odd-even effect as was observed for [n]-polyamides. The [n]-polyurethanes with branched alkylidene groups (3 f, g) show lower crystallinity (3 g) or are amorphous (3 f) materials. Upon heating, the [3]- and all the [4]-polyurethanes (3 a and 3 b, f, g) result in the corresponding cyclic urethanes by ring-closing depolymerization.