摘要:

AbstractA new approach to the problem of construction of efficient antimutagenic (at γ‐irradiation) systems has been developed on the basis of the models‐ synthetic cationic polyelectrolytes‐ polyquaternary salts of diallyldimethyl‐ammon

ISSN:1022-1360    

DOI:10.1002/masy.19981300103

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

ISSN:1022-1360    

DOI:10.1002/masy.19981300104

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA novel hydrophobic monomer, ethyladamantyl malolactonate, has been synthesized and copolymerized with benzyl malolactonate by anionic ring‐opening polymerization. The ratio of adamantyl monomer varied from 0 to 100 mol%. Deprotection of benzyl groups leads to a water soluble copolyester with carboxylic acid lateral functions which give a polyelectrolyte character to the corresponding polymers. The mixture of a copolyester containing 10% of adamantyl groups and a β‐cyclodextrin/epichlorohydrin copolymer in aqueous solution leads to a new pH‐dependant associating system. The solution behavior of this system was studied by viscosimetry as a function of pH, concentration and ratio of both copolymers. At the initial solution pH (pH=2), the copolyester adopts a coiled structure as a result of hydrophobic interactions between the pendant adamantyl groups. Consequently, no network formation is observed as shown by a very low viscosity. As the pH increase, the viscosity of the medium increases and reaches a maximum at pH=5. At this pH, the copolyester expands because of electrostatic repulsions between the carboxylate pendant functions. Consequently, the adamantyl groups are accessible and can be encapsulated into the β‐cyclodextrin cavities resulting in a significant increase of the

ISSN:1022-1360    

DOI:10.1002/masy.19981300105

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe graft copolymer, P(HBV‐g‐St), was synthesized by graft polymerization of styrene (St) onto poly(3‐hydroxybutyrate‐co‐3‐hydroxy valerate) [PHBV] under nitrogen atmosphere using benzoyl peroxide (BPO). The structure of poly[(hydroxybutyrate‐co‐hydroxyvalerate)‐g‐styrene][P(HBV‐g‐St)] was identified by FT‐K,1H‐NMR, and13C‐NMR spectra. The effects of weight ratio of St to PHBV in feed, initiator concentration, reaction time and reaction temperature on the grafting ratio and grafting efficiency were investigated. The thermal decomposition temperature of P(HBV‐g‐St) was 273°C. The tensile strengths of P(HBV‐g‐St) before and after photo‐ or biodegradation were also measured. The photodegradability of P(HBV‐g‐St) was better than that of PHBV. The film surface of P(HBV‐g‐St) treated withAspergillus niggershowed extensive grooves and pits as compared with the untreated P(HBV‐g‐St). It was found that the photo‐ and biodegradation rates of P(HBV‐g‐St) and tensile strength of P(HBV‐g‐St) can be

ISSN:1022-1360    

DOI:10.1002/masy.19981300106

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe objective of this research is to synthesize synthetic biodegradable polymers that would have biological functions similar to nitric oxide. Polyglycolide (PGA) was the synthetic biodegradable polymer and 4‐amino‐2,2,6,6‐tetramethylpiperidine‐1‐oxy (Tempamine) was chosen as the source of nitroxyl radicals. Tempamine nitroxyl radicals were chemically incorporated into the carboxylic acid chain ends of PGA macromolecules via amide linkage. The kinetics ofin vitrohydrolytic release of Tempamine nitroxyl radicals from the host PGA in buffered media at 37 °C was studied. Tempamine nitroxyl radicals were released into the media via cleavage of either ester linkages in the PGA segments or/and the amide linkage between Tempamine and the PGA segments. The duration of hydrolysis would determine the type of degradation products that were different in the segmental length of the PGA component. A preliminaryin vitrocell culture study of this new generation of biologically active biodegradable polymers indicated that it was able to retard the proliferation of smooth muscle cells as pure nitric

ISSN:1022-1360    

DOI:10.1002/masy.19981300107

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe films of poly[(R)‐3‐hydroxybutyric acid‐co‐10mol% 6‐hydroxy‐hexanoic acid] (P[(R)‐3HB‐co‐6HH]) were prepared by melt‐crystallized method at various crystallization temperatures. The morphologies and properties of melt‐crystallized films were characterized by means of x‐ray diffraction, differential scanning calorimetry, optical microscopy, and scanning electron microscopy. All of the melt‐crystallized films showed the banded spherulite morphology. The enzymatic degradation of melt‐crystallized films was carried out at 37 °C in an aqueous solution (pH 7.4) of PHB depolymerase fromAlcaligenes faecalis.The rate of enzymatic erosion was strongly dependent on the crystallinity of films, and the highest rate was as large as 2.15 mg·h−1·cm−2. After enzymatic degradation, the banded morphology of P[(R)‐3HB‐co‐6HH] spherulites was visible, suggesting that PHB depolymerase predominantly hydrolyzes polymer chains on

ISSN:1022-1360    

DOI:10.1002/masy.19981300108

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA series of symmetrical diols were synthesised through ring‐opening of lactones with different ring sizes by alkane diamines in moderate to good yields. Ring‐opening of the dilactones glycolide and lactide with a diamine in equimolar amounts afforded symmetrical diols in quantitative yield.Aliphatic poly(ester‐amide)s were prepared by polycondensation of N,N′‐bis(caproyl)butane diamide, dimethyl adipate and 1,4‐butanediol. The structure of the diamide was retained in the polymer. The polymers synthesized are semi‐crystalline materials that possess ordered structures in the solid phase over almost the entire copolymer range. Depending on thermal history and copolymer composition thermal analyses is in agreement with the presence of pseudo‐hexagonal crystal structures below 75°C, a fast melting recrystallization at this temperature and a triclinic structure at hig

ISSN:1022-1360    

DOI:10.1002/masy.19981300109

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractBiodegradable polyurethane urea fibers for ACL reconstruction have been produced by wet spinning. By using a short‐chain polyester diol as the soft segment in the polyurethane urea the elongation‐to‐break of the fibers have been reduced to be below 100% instead of 400–800% for spandex fibers, the modulus is increased from 5 MPa to 1 GPa and the tensile strength is increased from 0.1 N/tex to 0.4 N/tex. The composition of the polyester determines at which rate the fiber degrade. Different polyesters have been investigated to find the most suitable degradation rate for ACL appl

ISSN:1022-1360    

DOI:10.1002/masy.19981300110

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractCooligo(lactone) macromonomers were prepared by cooligomerisation of (S,S)‐3,6‐dimethyl‐1,4‐dioxane‐2,5‐dione (L‐lactide), 1‐oxacyclohexane‐2‐one (δ‐valerolactone) or 1‐oxacycloheptane‐2‐one (ε‐caprolactone), initiated by 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxypropoxy)phenyl]‐propane (BisGMA). Two different reaction ways were used for the synthesis: parallel reaction and step reaction of lactones and L‐lactide. The macromonomers were characterised by differential scanning calorimetry (DSC), size exclusion chromatography (SEC),1H‐ and13C‐NMR spectroscopy and MALDI‐TOF mass spectrometry. Cooligo(lactone) macromonomers prepared by parallel and by step reaction show different molecular structures resulting in different properties. Their glass transition temperatures depend on the molar ratio of lactide and lactone as well as on the degree of oligomerisation. Macromonomers with high a

ISSN:1022-1360    

DOI:10.1002/masy.19981300111

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractPolyurethane (PU) sheets were prepared from glucose‐, fructose‐and sucrose‐based polycaprolactones (PCL). The obtained saccharide‐based PCL's were characterized by gel permeation chromatography, Fourier‐transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The glass transition temperature, thermal degradation temperature, tensile strength, elongation and Young's modulus of the PU sheets were measured. The obtained results suggest that the molecular motion of PU's is enhanced with increasing fraction of PCL chains in PU molecules, and that at the same time the saccharide components act as hard

ISSN:1022-1360    

DOI:10.1002/masy.19981300112

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY