摘要:

AbstractThis paper presents information on the preparation of the network polyester films from glycerol (Yg) and aromatic dicarboxylic acids of phthalic anhydride (P), dimethyl isophthalate (I) and dimethyl terephthalate (T), as well as aliphatic dicarboxylic acids of adipic, sebacic, 1, 10‐decanedicarboxylic and 1, 12‐dodecanedicarboxylic acids, and their properties. Ygand dicarboxylic acid were polycondensed immediately before the gelation started. The prepolymers obtained were cast from DMF solution and successively post‐polymerized at various temperatures and times to form networks. The resultant films were transparent, flexible and insoluble in organic solvents. Heat distortion temperature (Th) measured by a penetration mode of thermomechanical analysis increased with increasing post‐polymerization temperature and time, and then leveled out.Thvalues corresponded well to the glass transition temperature (Tg) measured by differential thermal analysis (DTA).Thwas 152°C, 162°C and 197°C for YgP, YgI and YgT post‐polymerized at 270°C for 6 h, respectively.Thvalues of network films made from aliphatic dicarboxylic acids could not be observed until complete probe penetration occurs, as a result of thermal decomposition because theTgis lower than room temperature. The degree of reaction estimated from the IR absorbance of hydroxyl and methylene groups was in the range of 60–80%. Two diffraction peaks appeared in the wide‐angle X‐ray scattering pattern, suggesting some ordered structure owing to the regular networks. Density decreased with increasing post‐polymerization time and temperature, in the order YgP>YgI>YgT. Network films made from aliphatic dicarboxylic acids had much lower tensile strength and Young's modulus, and greater elongation, than those made from dicarboxylic acids, as a result of theTgbeing b

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330101

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolyacrylonitrile (PAN) films were made by casting a dimethyl sulphoxide (DMSO) solution. After drying, the films were uniaxially drawn by an essentially solid‐state drawing procedure. Using polarised‐infrared (IR) spectroscopy, the dichroism of the nitrile‐stretching vibration was monitored as a function of draw ratio. The dichroism results were converted to plots of chain‐orientation factor versus draw ratio. For this, α, the transition‐moment angle of the vibration, has to be known. Though a value of 68–73° has been suggested in the literature, for the present samples α cannot be 70° or less, and 73° is the most appropriate. The meaning and nature of the transition‐moment angle in the context of a flexible‐chain polymer molecule is discussed. The IR spectrum also showed dichroism in the SO stretch and the CH3rocking vibrations from the (residual) DMSO present in the film, indicating that the solvent molecules were also orientated. It is proposed that this occurred due to dipolar interactions between the SO and the CN groups, which led to solvent molecules being bound to the polymer chains. X‐ray diffraction studies indicated ‘lateral‐ordering’ consisting of hexagonally packed, rod‐like chains with noc‐axis order. The diffraction patterns obtained here were the ‘standard’ ones for PAN, in contrast to those observ

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330102

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractDebromination of poly(1,4‐phenylene sulphide), PPS, chains during formation by solution polymerisation of copper(I) 4‐bromobenzenethiolate, CBT, in quinoline and quinoline/pyridine mixtures at temperatures in the range 180–225°C has been investigated. The results are consistent with previously‐reported model compound studies and show that debromination is insignificant if the polymerisation temperatures is ≤ 200°C. Pyridine was shown not to be essential for the formation of high molar mass PPS. The optimum conditions for preparing high molar mass PPS in high yield with no significant debromination were polymerisation of CBT at a concentration of 1.0 mol dm−3in dry quinoline under a flowing dry nitrogen atmosphere at a controlled temperature of 200°C

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330103

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe optical activity of ten natural‐type polymers [poly(α‐aminoacids), polysaccharides, proteins and nucleic acids] was measured in solution, as solid powders in suspension, and where possible in the form of films. In some cases the specific rotation of powder samples showed significant differences to the values obtained from solution measurements. The discrepances seem to reflect the arrangements of polymer chains in supermolecular assemblies in the polymer solid s

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330104

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractHydrolytic degradation of intrinsically amorphous poly(DL‐lactic acid) was re‐examined in pH 7.4 isoosmolar phosphate buffer at 37°C. Size‐exclusion chromatogarphy, X‐ray scattering and differential scanning calorimetry were used to monitor molecular weight and morphology changes up to the ultimate degradation stage. It was found that heterogeneous degradation of poly(DL‐lactic acid) yielded a crystalline residual material of low molecular weight. Comparison with a stereocomplex made of equimolar poly(L‐lactic acid) and poly(D‐lactic acid) showed that the poly(DL‐lactic acid) degradation residue was actually an oligomeric stereocomplex. The formation of stereoregular oligomeric enantiomers agreed well with the predominantly isotactic structure of poly(DL‐lactic acid) obtained by ring‐opening polymerization ofDL‐lactide and argued in favour of the stereodependence of main cha

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330105

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe syntheses of polyenynes as model compounds for poly(diacetylene)s (PDAs) are described. Variation of properties (UV–VIS, Raman, NMR and bond geometries) as a function of the chain length was investigated. After extrapolation to infinite chain length these data were compared to those for PDAs. From UV–VIS spectra a value of λ = 551 nm (2.25 eV) was calculated corresponding to the electronic transition of a single polyenyne chain. This energy is located at the low energy end of a yellow PDA solution spectrum. From Raman scatteringv(CC)= 2108–2128 cm−1andv(CC)= 1505–1532 cm−1were calculated after extrapolation. Similarly sp‐C13C NMR data yielded a shift of δ = 100 ppm. These data are almost identical to data known for yellow PDA solutions. Bond geometries are almost identical to those of poly(diacetylene)s a

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330106

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA procedure based on sedimentation field–flow fractionation for physical characterization of polydisperse latexes is presented. The particle density, dimensions, polydispersity, size distribution and aggregation can be determined for both narrow and wide polydispersities. The procedure is applied to the sample case of polybutadiene latexes with density lower than water. The results are compared with independent measurements obtained by electron microscopy. The relevance of significant steps of the procedure, such as the nonequilibrium corrections, are discusse

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330107

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of poly(enamine ketone)s (PEAKs) which exhibit liquid crystalline phases has been synthesized. The enamine ketone groups are able to exist in thecisandtransconformations. Molecular modelling results show that thecisconformation is energetically more favorable due to intramolecular hydrogen bonding. Model compound studies indicate that the formation of the mesogen requires thecisconformation in the enamine ketones to stabilize the liquid crystalline phase. This liquid crystalline phase is nematic for the model compound and the polymers. The heats of liquid crystal transition in the model compound and in PEAKs are very close (4.7 kJ/mol in model compound and 4.0 kJ/mol of repeating units in polymers). This is not only an indication of a similar percentage of thecisconformation in both cases, but also an example that the flexible ethyleneoxy spacers in the polymers do not contribute to the orientational order of this liquid crystalline phase. PEAKs can crystallize through either quenching from the isotropic melt or from the liquid crystalline phase. Crystallization kinetics exhibit the effect of pre‐ordering when these two different kinetics are compare

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330108

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn order to study the promoting effect of polycations on the cobalt(II)phthalocyanine‐tetrasodiumsulphonate (CoPc(NaSO3)4)‐catalysed autoxidation of thiols, it is imperative to know the molecular weight dependence of the polymer. Monodisperse oligomers can often supply a lot of information. To elecidate the mechanism of the promoting effect of 2,4‐ionene, a poly(quaternary ammonium)salt, on the CoPc(NaSO3)4‐catalysed autoxidation of 2‐mercaptoethanol, a series of monodisperse 2,4‐ionene oligomers were prepared. Trimeric 2,4‐ionenes, containing two quaternary ammonium groups separated by four methylene groups, showed a high co‐catalytic activity, and active Co‐aggregates were detected with visible light spectroscopy. The spectroscopic behaviour was in close agreement with that of high molecular 2,4‐ionene/CoPc(NaSO3)4complexes. In order to achieve this aggregation several oligomeric ionenes have to act concertedly. If the distance between the ionic sites is short the trimer acts as a simple salt in stablizing the aggregates. With respect to the catalytic activity the optimum polycation/catalyst ratio, expressed as the N+/Co ratio, decreased with increasing chain lenght and reached a constant level of 50 at a 2,4‐ionene nonamer. For the trimers and pentamers this ratio is affected by the type of end‐group. All synthesized 2,4‐ionene oligomers exhibited excellent co‐catalytic properties at the optimum N+/Co ratio, with maximum turnover frequencies of 4600 mol thiol/(mol Co s), i.e. 50 times higher than those obtained for the polymer‐free system. In the case of monodisperse 2,4‐ionene pentamer with bromo end‐groups, double Michaelis–Menten kinetics were observed, as also was exhibi

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330109

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolydiacetylene (2) of varying molecular weight has been formed by UV‐ or60Co γ‐irradiation of the diacetylene PhCH2CO2(CH2)9‐CCCC(CH2)9O2CCH2Ph (3), with conversion of 30−>95%. Samples of (2) with differing physical properties have been studied, in the bulk phase, by CPMAS13C NMR and VIS/UV spectroscopy and by DSC; complementary spectroscopic data on solutions of (2), including fluorescence studies, are also reported. Spectroscopic studies support the presence of an extended planar conjugated backbone in ‘as polymerised’ blue–black samples of (2), from which various forms of red‐coloured polymer, with shorter conjugation lengths, can be obtained. Studies of the thermal behaviour indicate the existence of several differing thermal transitions for these materials and the

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330110

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY