摘要:

AbstractChemical reactions leading to crosslinking were followed by rheometrical studies during curing at different temperatures and compositions of compatible species. The condensation reactions between two copolymers of styrene and maleic anhydride, and several α,ω‐dihydroxyoligostyrenes, lead to an experimental variation of the elastic modulus (G′)t. A kinetic scheme is proposed, selecting the most reliable reactions, which describes the experimental behaviour adequately. According to this scheme, the rate constants of interpolymeric condensation reactions were evaluated. It appears that the values obtained for grafting and crosslinking are quite the same. They depend mainly, in absence of a catalyst, on the molecular weight of the oligomer and on the local viscosity, which is a function of composition. In presence of a catalyst, there is a large increase of the constant, indicating that the chemical step is dominating the diffusion pr

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891201

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe copolymerization of sulfur dioxide with methyl, ethyl, butyl or 2‐ethylhexyl acrylate was studied. The influence of the composition of monomer feed and reaction temperature on the composition of the copolymers was investigated. The maximum content of sulfonyl units in the copolymers, obtained at −78°C, was found to be ca. 30 mol‐% and to decrease with increasing temperature. The sequence distribution in the copolymers was determined by13C NMR spectroscopy. It was proved that acrylates do not undergo alternating propagation with SO2, and the minimum number of acrylate monomeric units in a homosequence is 2. The results obtained were compared with those obtained from studies on the copolymerization of SO2, with other monomers, and are discussed in terms of the alternating copolymerization theory and the penultimate

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891202

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effects of three cationic surfactants, dodecylammonium chloride (C12N+), dodecyldimethylammonium chloride (C12N+2C1), and dodecyltrimethylammonium chloride (C12N+3C1), on the permeability of 1‐phenyl‐1,2‐ethanediol were investigated for the membrane of poly[butyl methacrylate‐co‐N‐methyl‐N‐(4‐vinylphenethyl)ethylenediamine]‐graft‐poly(L‐glutamic acid) (PLGA)(1b), the permeating pathway being composed of the polypeptide domain. The membrane treated with a surfactant shows a decrease in permeability due to the coil‐to‐helix transition of PLGA induced by the surfactant. The effects of the three surfactants on the permeability was found to be of the ord

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891203

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractAlkyl, alkenyl, and alkoxy substituted dicyclopentadienyltitanium (or zirconium) dichlorides were condensed with diacids, hydroxyacids or diphenols to give metal containing polyesters, poly(ether‐ester)s, and polyethers, most of them being new. Experimental parameters were investigated, including stirring rate, reaction time, reaction temperature, steric hindrance, ratio of reactants, and reactivity of the reactants. Determinations of color‐change temperatures, solubilities and molecular weights were carried out as well as TG, DTG and IR spectroscopy of the resulting polym

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891204

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThermotropic liquid‐crystalline poly(1,4‐phenylene terephthalate)s with phenylalkyl side chains were synthesized. The influence of this novel type of substituent on the thermal properties and solubility behavior is discussed. In common solvents soluble, liquid‐crystalline polyesters with low transition temperatures were obtained when the phenylalkyl substituent was introduced in combination with a bulky substituent or when both phenyl rings were substituted with phenylalkyl side chains. When poly(1,4‐phenylene terephthalate) is only monosubstituted with a phenylalkyl substituent in the 1,4‐phenylene unit, the polyesters have melting temperatures above 310°C and are only soluble in solvents such asp‐

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891205

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe photodecomposition of diphenyl‐2,4,6‐trimethylbenzoylphosphine oxide(1)was studied both in solution at 40°C and in thin films in the presence of 1,1‐di‐p‐tolylethylene as a model substrate for vinyl monomers. Both primary radicals resulting from α‐cleavage of1were found to add to the olefinic double bond of the model substrate (initiation). The diphenylphosphinoyl radical(3)proved to be twice as effective as the 2,4,6‐trimethylbenzoyl radical(2)under all conditions. Oxygen (air) considerably reduced the initiating efficienciesfp, in particularfp(2)(of radical2). The addition of triethylamine partially restored the overall initiating efficiency in all likelihood by oxygen scavenging. A direct contribution of triethylamine‐derived radicals to the initiation

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891206

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

Abstract1‐Alkanesulfonic and 4‐alkylbenzenesulfonic esters of α‐hydroxymethylbenzoin were shown to photoinitiate the polymerization and crosslinking of acrylates. The overall rate of polymerization in bulk and of crosslinking in solution, respectively, proved to be constant within each series of homologues. However, in thin films in an air atmosphere, the overall rate of crosslinking (curing rate) proved to increase with increasing alkyl chain‐length within each series of homologues. Moreover, the curing rate obtained with the 1‐hexanesulfonic ester and its higher homologues substantially surpassed the curing rates obtained with a number of established photoinitiators, provided a small amount of an alkali metal salt (preferably a lithium salt) is present. The curing mechanism of the sulfonic esters of α‐hydroxymethylbenzoin and the role of the alkali metal salt

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891207

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe possibility of making block copolymers at room temperature from the monomer pairs2a,b/1, 4/1, 5/1and5/3 (1= norbornene = bicyclo[2.2.1]hept‐2‐ene;2a,b=anti‐ andsyn‐7‐methylbicyclo[2.2.1]hept‐2‐ene;4= methylendo‐bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate;5=endo‐bicyclo[2.2.1]hept‐5‐ene‐2‐carbonitrile;3= 1,5‐cyclooctadiene) was explored using as initiator of metathesis polymerization in CD2Cl2. The reactions of successive small amounts of the monomers with the catalyst were first followed by1H NMR to determine the rate of the reaction and the stability of the metal‐carbene propagating species. AB and ABA type block copolymers were prepared on this basis and analysed by GPC. An increase in molecular weight after each addition was observed in most cases. Secondary metathesis reactions of double bonds in the polymer chains appear to be sig

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891208

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe free radical oligomerization of methyl methacrylate using different tetraphenylethane initiators [1,2‐diphenoxy‐1,1,2,2‐tetraphenylethane(4), tetraphenylsuccinonitrile(5), and 1,1,2,2‐tetraphenyl‐1,2‐bis(trimethylsiloxy)ethane(6)] gives telechelics1 – 3with end groups originating from the initiator. These telechelics were characterized by gel permeation, thin layer, and high performance chromatography. By adsorption chromatography, the separation does not only proceed in accordance with the molecular weight of the oligomers, but also with their tacticity as well. The free radical oligomerization is a process in which syndiotactic structures are favoured above i

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891209

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe commercially available poly(1‐octenylene) Vestenamer® formed by the metathetic polymerization of cyclooctene with a tungsten catalyst, is highly crystalline at room temperature; it shows specific properties as a blend component, thus favourably influencing the processing characteristics and the final product quality. Differential scanning calorimetry, infrared and torsion pendulum experiments indicate that the melting temperature and the degree of crystallinity depend on the concentration of trans double bonds, on their distribution along the polymer chain as well as on the sample history. The formation of crosslinks induced by very intensive UV irradiation of 100 μm thin films leads to a reduction of the melting temperature and the crystallinity. A correlation between stiffness (shear modulusG′) and crystallinity was found for samples with varying amounts of trans double

ISSN:0025-116X    

DOI:10.1002/macp.1988.021891210

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY