摘要:

AbstractThe “criss‐cross” cycloaddition reaction between derivatives of benzaldehyde azine and several diisocyanates is used for the synthesis of polymers with an uncommon structure element: the 1,3,5,7‐tetrazabicyclo[3.3.0]octane‐2,6‐dione. The nature of the diisocyanate determines the reactivity in this cycloaddition polycondensation and the solubility of the new polymers. A degree of polymerization up toPn= 72 could be achieved. Due to the nature of the polycondensation reaction, the polymers have two isocyanate end‐groups, independent of the stoichiometry of the monomer mixture at the beginning of the reaction. Thus, a prepolymer was synthesized and the chain extension by reaction of its isocyanate end‐groups with diamines was studied

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940901

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe physical state of water in poly(vinyl alcohol) (PVA) hydrogels was studied with differential scanning calorimetry to elucidate their microstructure. PVA hydrogels were prepared after three different methods, viz. chemical crosslinking with glutaraldehyde, annealing of dried film and crystallization at low temperature. The water in PVA hydrogels could be classified into three types: free water, intermediate water and bound water. The concentration of bound water is practically not dependent on the total water content of the hydrogels when prepared by low‐temperature crystallization or annealing of the PVA film. The gel prepared by low‐temperature crystallization contained less bound water than the gel obtained by annealing of a cast film. Furthermore, the concentration of bound water increases as the degree of polymerization (DP) of PVA increases, whereas the reverse tendency was observed for the intermediate water. From these results it was concluded that the low‐temperature crystallization method results in a larger free space between the PVA microcrystallites and a larger size of microcrystallites than the annealing method. It is also likely that PVA of higher DP provides a larger amount of free PVA chains which are not involved in microcrystal

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940902

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractMeasurements on polyaniline using dielectric analysis (DEA, −50°C to 240°C, 0,4 Hz to 105Hz), differential scanning calorimetry (DSC, 30°C to 240°C) and infrared spectroscopy (IR) after heat treatment from 25°C to 300°C are carried out. After conversion of DEA results to complex electric modulus, the conductivity relaxation time distribution can be obtained, which remains unchanged for temperatures below 160°C and becomes narrower in the temperature range from 180°C to 240°C due to the occurrence of crosslinking reactions, as is confirmed by the exothermic behavior above 160°C and by the decrease of the relative intensity of quinoid absorption with respect to that of the aromatic ring. The crosslinking reaction causes a decrease in dc conductivity, a narrowing in conductivity relaxation time distribution and an increase in activation energies for conductivity and conductivity

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940903

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractNew sulfur‐containing polycarbonates have been prepared by interfacial polycondensation of 4,4′‐isopropylidenedibenzenethiol with phosgene, bisphenol‐A bischloroformate and bisphenol‐A polycarbonate oligomers (OH/OCOCl terminated); high‐molecular‐weight polymers were obtained. The influence of the nature of the phase transfer catalyst on the yield and on the molecular weight of the polymers was studied. From thermogravimetry (TG) analysis it was possible to observe that the substitution of the oxygen atoms by sulfur atoms leads to less thermally stable polymers compared with the corresponding polycarbonate (bisph

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940904

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractL‐ andD,L‐lactide copolymers with 6‐caprolactone were synthesized and characterized in a wide range of compositions. The polymerizations were carried out in batch at 130°C, with Sn(II) octoate as a catalyst, a monomers/initiator mole ratio of 5000/1 and a reaction time of 48 h. The copolymers having from 5 to 40 wt.‐% of 6‐caprolactone are characterized by higher values of non‐reacted monomers and deviations of the polymer composition from the feed ratio. In the same interval of compositions,L‐lactide copolymers showed progressive hardening with time at room temperature, attributable to the tendency to crystallization of homopolymeric sequences. This behaviour was more deeply studied in the case of poly(L‐lactide‐co‐6‐caprolactone) with 30 wt.‐% of 6‐caprolactone.1H NMR at 300 MHz appeared to be a suitable method for the determinati

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940905

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe free‐radical terpolymerization of ethene, acrylonitrile and vinyl acetate was studied at 2000 bar in the temperature range from 170°C to 240°C in a continuously operated tubular‐type reactor. Polymerization was induced either thermally or chemically by di‐tert‐butyl peroxide as the initiator. Addition of vinyl acetate to ethene and acrylonitrile substantially enlarges the range for polymerization in the homogeneous fluid phase as compared to the binary copolymerization of ethene with acrylonitrile; a terpolymer with a high content of nitrile functional groups can be obtained from a single‐phase reaction. The six reactivity ratios of this terpolymerization,rEA,rEV,rAE,rAV,rVEandrVAare derived by applying first‐order Markov‐chain simulations. As ethene is the major component in the monomer mixtures,rEAandrEVare obtained with higher accuracy. ForrEAthe Arrhenius expressionrEA= 2,6 · exp(−2,1 · 103· (T/K)−1) is found (for 2000 bar).rEV= 0,9 ± 0,2 appears to be independent of temperature. The accuracy of the reactivity ratiosrVE,rAV,rVAandrAEis not sufficient to detect a temperature dependence. The terpolymerization is also treated as a quasi binary copolymerization of ethene/vinyl ac

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940906

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractHomogeneous and flexible films of polythiophene are known to be difficult to obtain electrochemically on indium tin oxide (ITO) glass electrodes using normal 1,6–1,7 V applied voltage. The situation is greatly improved by using higher voltage. 0,1–10 μm thick films of polythiophene (PT) and various poly(3‐alkylthiophene)s (P3AT's) (alkyl = methyl (P3MT), hexyl (P3HT) and octyl (P3OT)) were electropolymerized on ITO‐covered glass anodes under an applied voltage of 8 V vs. an Ag/AgCl reference electrode. In this paper we report upon the properties of these films compared to their chemically and at low‐voltage electrochemically polymerized equivalents. Generally, the films have all the properties known for PT and P3AT's. Characteristics such as thermo‐ and solvatochromism, conductivity and electronic band structure as studied by ultraviolet photoemission spectroscopy and optical absorption were comparable to the properties shown by the reference samples. However, the structure of high‐voltage films differs considerably from those reported for chemically polymerized samples. The high‐voltage films contain a higher amorphous fraction, and the polymer is more cross‐l

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940907

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractSolubilization of poly(isobutene)Systematic IUPAC name: poly(1,1‐dimethylethylene).by micelles of polystyrene‐block‐poly(ethylene/propene) block copolymer with a copoly(ethylene/propene) core was investigated. The weight of poly(isobutene) solubilized was found to be proportional to the concentration of block copolymer in the solution. No influence of the presence of poly(isobutene) on the critical micelle temperatures has been found. However, the addition of poly(isobutene) to the micellar solution seems to favour the anomalous behaviour found in micellar solutions of the block copolymers used in this

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940908

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractSynthesis of polymers with aldehyde or ketone groups at both chain ends was carried out by oxidation of polymeric terminal diols with an oxoaminium salt (OAS), the oxidized form of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl. Terminal diols of polyethers, polyesters, polycarbonates, polybutadiene, and hydrogenated polybutadiene were oxidized with 2,0 equiv. of OAS in dichloromethane at room temperature in the dark. The corresponding aldehyde‐and/or ketoneterminated polymers were obtained in high yields with high conversion of OH group and little change in molecular weight. Poly(ethylene glycol) and poly(ethylene adipate) terminal diols were oxidized with low efficiency. Especially, in the case of poly(ethylene glycol), intermolecular reactions occurred to afford high molecular weight polymer. The ratio of aldehyde (CHO) to ketone (CO) groups in the oxidized polymer originating from the hydrogenated polybutadiene terminal diol was calculated to

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940909

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA series of side‐chain Iiquid‐crystalline polymers was prepared containing disiloxane units in the spacer. The polymers consist of a polymethacrylate backbone and several kinds of mesogenic side groups. For the synthesis of the desired monomers, silanol compounds carrying a mesogenic groups were prepared as the intermediates. The polymers were obtained by ordinary free‐radical polymerization. As the mesogenic groups, linear‐typep‐ orp′‐substituted phenyl and biphenylyl benzoates,p‐ orm‐substituted benzoyloxybiphenyl groups and laterally attached biphenylyl benzoate‐type mesogens were chosen, and the structural effects on the thermal properties of the polymers were investigated. In the case of linear‐type mesogens, only when triple‐core mesogens were introduced a stable smectic mesophase was observed with a wide range of phase stability, while on mesophase was observed for the linear double‐core and the laterally attached mesogens. On the other hand, a highly ordered smectic phase was observed for polymers having linear‐type triple‐core mesogens withp‐alkoxy andm‐cyano end groups. Furthermore, it was revealed that the introduction of a disiloxane unit in the spacer lowered the temperature range of the mesophase, in comparison with polymers having an alkylene spacer with the sam

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940910

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY