摘要:

AbstractA new approach to the synthesis of thermotropic liquid‐crystalline (LC) polymers is described based on the polymerization of monomers containing various mesogenic groups attached to the backbone chain by flexible polymethylene spacer groups. Dozens of new LC polymers are described, including derivatives of polymethacryloyl L‐lysine, cholesteric esters of long‐chain aminocarboxylic acids, and other aromatic polymers. Phase transition temperatures, heats of fusion, and x‐ray structural analysis were evaluated. Polymers exhibiting spontaneous optical anisotropy in the glasslike, elastic, and fluid states are described, and schemes of molecular packing in the LC phase are proposed. We show the possibility of realizing smectic, nematic, and cholesteric types of structures in these thermotropic LC polymers. An LC structure for various comblike copolymers not having mesogenic groups at every monomeric unit was detected. The role of specific interactions in side groups and their mobility in allowing for the LC structure are discussed, and the necessity of having particular conformations of the macromolecules is shown to provide the LC structure in films made from various so

ISSN:0360-8905    

DOI:10.1002/polc.5070670103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractIn this paper different examples of the effect of coordination‐unsaturated metal compounds on the radical homo‐ and copolymerization of vinyl monomers are considered and analyzed. In all known cases homopolymerization proceeds according to the usual addition chain radical scheme and involve an initiation step with the formation of a primary radical. Complexed radicals or monomers take part in the chain propagation steps. In the case of copolymerization, a complexing agent can considerably influence apparent relative activities of monomers, decreasing or increasing the tendency to alternation. If two monomers are present in the system, one of which forms a complex with a Lewis acid, and the other is a donor with respect to this complex, the formation of a ternary donor‐acceptor complex also occurs in a number of cases. A ternary complex can fulfill the monomer function in the chain propagation reaction, i.e., it can add to the propagating chain as an independent kinetic species. In such cases, strictly alternating copolymers may be obtained. All mechanisms considered agree with the addition‐polymerization scheme. From the kinetic point of view the ternary complex addition is somewhat similar to an elementary step of Butler's inter‐intramolecular cyclopolym

ISSN:0360-8905    

DOI:10.1002/polc.5070670104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractConsiderable confusion exists in the literature concerning the structure and properties of polyarylacetylenes. Taking into account the significant structural aspects from the literature data with our recent results on the polypentadeuterophenylacetylene isomers, we present our findings concerning this class of polymer.

ISSN:0360-8905    

DOI:10.1002/polc.5070670105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe reaction mechanism of the stereoselective polymerization of methyloxirane is satisfactorily explained in terms of the enantiomorphic catalyst sites model, in which the symmetrical distribution ofd*, andl*, catalyst sites is assumed.d*, Sites would accept D‐methyloxirane in preference to the L‐isomer, resulting in the formation of … DDDD … isotactic sequences, and vice versa. This paper is concerned with a mechanistic study on the origin ofd*andl*nature of the catalyst by using a complex, [Zn(OMe)2‐(EtZnOMe)6] (I), the molecular structure of which was elucidated by x‐ray analysis. A possible mechanism for the stereoselective polymerization of methyloxirane is presented on the basis of results obtained from NMR analysis of the polymerization system catalyzed by (I) and GPC analysis of poly(methyloxirane) formed in the reac

ISSN:0360-8905    

DOI:10.1002/polc.5070670106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractPhotochemical and thermal dissociation of labile molecules in the solid state or dissolved in solid polymer matrix affords reaction products which differ in composition and relative amounts from those obtained in solution. These differences are interpreted on the basis of limited rotation and diffusion possibilities. When the dissociation produces reactive species which can recombine thermally or photochemically, the kinetics do not follow a bimolecular reaction mechanism, as in solution experiments. On the contrary, they show a stepwise process, that has been described by Waite, Lebedev, and Butyagin. As a first step, rapid “cage recombination” occurs, followed by a second very slow step corresponding to the diffusion‐controlled recombination of isolated species (radicals or monomers). These stepwise reaction kinetics are illustrated by three different dissociation–recombination equilibria.a.thermaldissociation of benzpinacol and its derivatives and radical recombination.b.photochemicaldissociation of hexaphenyl‐1.2′‐bisimidazole into triphenyl‐imidazolyl radicals and their recombination.c.photochemicaldissociation of substituted anthracene‐ and (benz)acridizinium dimers andphotochemicalrecombination of monomers In (b), radical pairs and isolated radicals can easily be distinguished by ESR. On the basis of Waite's rate equations, the diffusion coefficient of the radical and the “cage” dimension can be calculated. The cage dimensions agree with these determined by Butyagin for radical decay on γ‐irradiated polymers. Experiments at different temperatures (below and aboveTg) stress the influence of the segmental mobility of the polymers, as well as of the molar volume

ISSN:0360-8905    

DOI:10.1002/polc.5070670107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractExperimental data have been obtained evidencing the chain character of cyclo‐olefin ring‐opening polymerization and the carbene nature of the active centers in this reaction. The formation of metal–carbene complexes via the decomposition of organometallic derivatives of tungsten, molybdenum, and tantalum has been investigated. The mechanism of the chain propagation in cycloolefin polymerization and olefin metathesis as well as the mechanism of cyclodestruction of unsaturated polymers are discussed. The possibility of the inhibition of the chain metathesis process by carbene complexes more stable than active centers of the growing chain is

ISSN:0360-8905    

DOI:10.1002/polc.5070670108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractA special way of coupling a thermobalance and a quadrupol mass spectrometer proved to be a source of complex information on the structure and degradation of polymers. Two typical examples—polypropylene and polyquinone—were investigated. The most important new findings in the case of polypropylene were connected with the influence of the layer thickness on the thermal stability and the formation of volatile products. New light could be thrown on the mechanism of degradation based on the results. In the case of the new polymer, polyquinone, the effect of the imperfections of structure could be well separated from the basic process of thermal breakd

ISSN:0360-8905    

DOI:10.1002/polc.5070670109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractA review of reactive carriers and immobilized enzymes describing the latest developments in the authors' laboratories is presented. Slightly basic and amphoteric reactive carriers were synthesized on the basis of poly (ethylene imine), and neutral hydrophilic carriers were obtained on the basis of polyethers. A new possibility for the Ugi reaction including carbon dioxide as the fifth component in this reaction is shown. Crosslinked acrylic acid–styrene copolymers and also poly(vinyl alcohol) were used for the introduction of maleimide groups, giving polymers with a specific reactivity towards SH‐groups containing enzymes resp. thiolated enzymes. A poly(vinyl alcohol) containing fiber material, synthetic pulp, was modified with diazonium groups and used for the immobilization of different enzymes. The properties of the immobilized enzymes were investiga

ISSN:0360-8905    

DOI:10.1002/polc.5070670110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070670111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe cost for a mole of radicals from different sources is under the assumptions used, as follows: $0.85 using dibenzoylperoxide, $5.60 with60Co, and $5.60 using a small 0.2‐MeV accelerator. Fluorine‐containing monomers and monomer mixtures belong to the most interesting class of systems for the radiation‐initiated synthesis of polymers with good thermal, mechanical, and chemical properties. Recently, the vinylfluoride‐vinylidenefluoride system was investigated in detail. The polymers were afterwards grafted with hydrophilic monomers.Films from, for example, polyethylene, polypropylene, polyvinylfluoride, or polytetrafluoroethylene were grafted from the gas phase with butadiene, vinylchloride, and styrene. Usually, homopolymerization in the gas phase can be kept low. A highly interesting system both from a theoretical perspective and for practical reasons is polyethylene‐hexafluoroacetone. The grafting follows a chain mechanism, and the “branches” consist of only one monomer unit each. Cationic grafting was observed during the irradiation of α‐methylstyrene, vinylbutylether, or isobutene in the presence of polyethylene, polytetrafluoroethylene, or PVC. A tremendous amount of work has been done in the field of radiation grafting of fibers and fabrics. In recent years, the following fiber/monomer systems, among others, have been investigated: cellulose with styrene, vinylfluoride. ethylacrylate, or acrylamide; wool with styrene; polypropylene with vinylchloride and vinylidenechloride; poly‐(ethylene terephthalate) with styrene, acrylic and methacrylic acid, acrylic acid plus acrylonitrile, andN‐vinylpyrrolidone.Special applications including radiation synthesis and modification of membranes and hydrogels, biocompatible materials, ion‐exchange membranes and resins, and, finally, the radiation‐grafting of enzymes have fou

ISSN:0360-8905    

DOI:10.1002/polc.5070670112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY