摘要:

AbstractNew hydrophobic‐hydrophilic microphase‐separated block segmented copoly(urethane‐urea)s were synthesized by introducing hydrophobic polybutadienes as the soft segments and 4,4′‐methylenediphenyl diisocyanate, hexamethylene diisocyanate, ethylenediamine, and a hydrophilic phosphatidylcholine analogue as the hard segments in the backbones of these polymers. The results of ATR‐IR and XPS show the coexistence of phosphatidylcholine analogues and polybutadienes on the surface of cast films of the synthesized poly(urethane‐urea)s. Furthermore, TEM cross sectional observation of the cast film PBDP‐1370 indicates that it possesses a hydrophilic‐hydrophobic microphase‐separat

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970501

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe preparation of polystyrene with controlled molar masses and narrow dispersity endcapped with an anthrylmethyl ether group, as well as the study of their photophysical properties, are described. Under irradiation at 336 nm dimerisation of the polystyrene chains is observed. This process results from the formation of a symmetrical head‐to‐tail photodimer between two anthryl end groups. When irradiated at lower wavelength (λ = 228 nm), the original ω‐anthrylpolystyrene chains are quantitatively restored. These dimerisation/dissociation cycles can be conducted more than ten times without any detectable degradation of the photosensitive polymer. The fluorescence emission quantum yield and fluorescence lifetime of the ω‐anthryl moieties and the quantum yield of the dimerisation and of the reverse process have bee

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970502

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe describe the preparation of telechelic OH‐terminated poly[(R)‐3‐hydroxybutyric acid] (PHB) and poly{[(R)‐3‐hydroxybutyric acid]‐co‐[(R)‐3‐hydroxyvaleric acid]} (PHB/HV), on a semi‐preparative scale, by a transesterification procedure from the high‐molecular weight polymers. The oligomers have well‐defined reactive end groups and are well suited for the preparation of high‐molecular‐weight block co

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970503

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA mathematical model of the polymerization process is suggested on the basis of kinetic data, obtained for the polymerization of ethylene with supported titanium‐magnesium catalysts of various compositions differing in particle size, content of electron donor modifier, oxidation state of titanium in the initial catalyst and combination with different cocatalysts. The model includes stages of the formation and deactivation of active sites and takes into account monomer diffusion into the polymer particle. The analysis of experimental data by means of the mathematical model allowed to obtain the rate constants for single stages of the polymerization process. The suggested model and the obtained set of parameters allow to make a satisfactory description of a wide spectrum of experimental data, corresponding to different shapes of kinetic curves. The kinetic parameters were found to depend on the oxidation state of titanium in the catalyst and on the nature of the cocatalys

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970504

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThermal and microwave‐activated ring‐opening polymerization at 180°C in the presence of titanium tetrabutylate at different ε‐caprolactone/titanium tetrabutylate molar ratios were compared. A special equipment was developed to control polymerization in the microwave field and to simultaneously monitor viscosity build‐up as well as changes in microwave powers corresponding to input, reflection and transmission. Conversion, measured by means of viscosity build‐up, and number‐average molecular weight of poly(ε‐caprolactone) were similar for both processes and did not indicate advantages relating to the use of micro

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970505

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe morphology of a novel poly(aryl ether ketone) [PEDEKmK] was investigated via polarizing optical microscopy (POM), TEM, DSC, SAXS and electron diffraction (ED). A distinct change in lamellar thickness, orientation, and spherulitic morphology was observed due to crystal melting and recrystallization. However, the crystal packing mode is found to be identical before and after the recrystallization process.

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970506

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA new commercial radically obtained hydroxytelechelic polybutadiene (HTPB‐A) was examined by1H NMR at 500 MHz, and a corrected interpretation of the complex proton methylene resonance of the vinyl‐type primary alcohol was done. The weight‐average hydroxyl functionalityF̄w(OH) was determined by using critical conversions at gel points of the (HTPB‐A + diisocyanate) systems, on the one hand, and swelling at equilibrium on the other. The functionality polydispersity index of HTPB‐A is clos

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970507

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA new synthesis of poly(L‐cystyl‐L‐cystine) by usingN,N′‐bis(trimethylsilyl)cystine dibenzyl ester is described. The polycondensation of the latter withN,N′‐bis(benzyloxycarbonyl)cystine bis(pentafluorophenyl) ester allowed us to obtain polymers having higher molar masses (28 700 instead of 14000 g/mol) and improved properties compared with earlier methods. The partial as well as complete deprotection of the polymer using a new method, generally used in peptide chemistry, is a

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970508

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe synthesis of two new isomeric asymmetrically disubstituted disulfide monomers, [4‐(3‐hydroxyphenylthio)benzoic acid and 3‐(4‐hydroxyphenylthio)benzoic acid], with potential applications as all‐aromatic polymer chain flexibilizers and flame‐retardant additives, is here reported. The preparation and characterization of their homo‐ and copolymers obtained with 4‐hydroxybenzoic acid, terephthalic acid and hydroquinone or its phenyl and methyl derivatives is also described. The purity of the monomers has been determined by gas chromatography, elemental analysis and NMR spectroscopy. Both monomers and polymers have been characterized by several techniques. DSC analysis and optical microscopy in polarized light have been used to determine the phase behaviour of the polymers. The remarkable differences in crystallinity and mesogenicity of the polymers derived from the two isomeric monomers are compared to the behaviour of copolymers containing the analogous oxygen‐

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970509

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA Raman spectroscopic study on property changes of water in aqueous gelatin media was carried out. The state of water in gelatin gels and sols at various temperatures and concentrations was studied in connection with the conformation of polymer chains. When gelatin with a low molecular weight was used, there was no gel‐sol transition, and the structure of water observed by Raman spectroscopy was not significantly affected by the presence of gelatin. When gelatin with a high molecular weight was used, on the other hand, the structure of water strongly depended on the concentration of gelatin both in the gel and the sol state. A contribution of small spaces surrounded by entangled gelatin chains (which exist both in high concentration gels and sols) to the perturbation of the structure of incorporated water was suggested. It was also found that, at 60°C, gelatin chains in the low concentration region induced an enhancement of structured water. This is the first finding that water soluble polymers at high temperature induce the network structure of wat

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970510

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY