摘要:

AbstractThe computer simulation of macromolecular materials has to deal with phenomena on length scales from 1Å to 100Å, as well as with time scales ranging over many orders of magnitude, and thus still presents a challenge. With suitably coarse‐grained models which disregard detailed information on chemical structure nevertheless collective phenomena can be described, such as unmixing of polymer blends, mesophase ordering of block‐copolymer melts, “blob formation” in semidilute solutions, etc. Simulations of such models provide a sensitive test of approximate theories and give valuable hints for ex

ISSN:0258-0322    

DOI:10.1002/masy.19910500103

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractMixing of viscous liquids is of common occurence in polymer technology. We consider the effects of mixing on the simplest bimolecular reaction A+B→O. Under mixing often lamellar arrays of striations of the A and B reactants are formed. The structure of these arrays and the thinning of the striations during mixing determine the kinetics of the reaction. We consider both a premixed situation (where the reaction is diffusion‐controlled) and also a situation where mixing and reaction take place simultaneou

ISSN:0258-0322    

DOI:10.1002/masy.19910500104

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractPolyetherimide is a high‐performance polymer which can be extruded to fibres and filaments. The threads are amorphous and have a smooth and closed surface. The material can be drawn and subsequently processed to textiles in the conventional way. Filaments of polyetherimide are flame‐resistant. The chemical resistance of polyetherimide is good; the polymer is particularly resistant to diluted acids, salts and oxida

ISSN:0258-0322    

DOI:10.1002/masy.19910500105

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractHomopolyamides and copolyamides with structural characteristics such as bulky lateral substituents, non‐coplanar, 2, 2′‐dimethylbiphenylene units and comonomers of different length were prepared and their structure‐property relations investigated. Polyamides with high solubilities and very low or no degree of crystallinity are obtainable by a combination of monomers with bulky lateral substituents and non‐coplanar biphenylene units. These polyamides form tough, transparent films with good mechanical and thermal properties. Lyotropic liquid crystalline behavior was found in some cases for polyamides with non‐coplanar biphenylene units. The incorporation of monomers with bulky substituents on the terephthalic acid unit lowers the chain stiffness and significantly influences the formation of lyotropi

ISSN:0258-0322    

DOI:10.1002/masy.19910500106

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractWith the increasing demand for polymers as materials for construction, the exact analysis of their mechanical properties in general and of their viscoelastic performance in specific becomes of increasing importance. An analytical model is introduced which enables to systematically describe the influence of strain on the stress relaxation performance of Kevlar®, Nomex®, and Technora®. The analysis is based on a two‐phase model, comprised of an elastic and a viscoelastic contribution and a shape‐invariate relaxation function. The change of the phase moduli and of the mean relaxation times with strain is documented for the three aramid fibers and discussed with respect to their morphological stru

ISSN:0258-0322    

DOI:10.1002/masy.19910500107

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractMembranes, as part of technical processes, are gaining more importance in areas such as chemicals, biotechnology or waste‐water treatment. The use of high performance polymers as membrane materials offers unique combinations of properties and allows new applications. Three different approaches towards membrane fabrication from high performance polymers such as polyaryls or polyaramides are discussed, i. e. maintenance of the polymer structure during processing and synthesis of better soluble structures via either polymer‐analogous reactions or tailor‐made copolymers. Examples of chemistry, property profiles and potential applications are

ISSN:0258-0322    

DOI:10.1002/masy.19910500108

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe gas permeability and sorption of CO2and N2O was measured on cardo‐poly(ether‐ether‐ketone) (C‐PEEK) and poly(phenylene sulfide) (PPS) at 298 K. The results are discussed on the basis of the dual‐mode model. Results obtained from measurements at 308 K are compared with literature data of poly(phenylene oxide) (PPO), poly(sulfone) (PSU) and poly(carbonate) (PC). While C‐PEEK shows similar transport properties as PC and PSU, the values of PPS are distinctly lower. The solubility of CO2in the various polymers as well as the correlation of the permeability coefficients of the same polymers for He, Ar, CO2, N2, and CH4with the kinetic molecular diameter of the gases indicate a simple relation of the transport properties with the poly

ISSN:0258-0322    

DOI:10.1002/masy.19910500109

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA new concept of “molecular computing” based on spectral hole‐burning, the interaction of molecular energy levels with an externally applied electric field and the interferometric properties of holography is presented. The molecular processor introduced here relies on the spectroscopic properties of a dye doped polymer film, which simultaneously can be used for image recording and for parallel processing of the stored inform

ISSN:0258-0322    

DOI:10.1002/masy.19910500110

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractBacteriorhodopsin (BR) from Halobacterium halobium [1] is embedded as a twodimensional crystalline lattice of BR‐trimers in the lipid bilayer of the cell membrane [2]. BR consists of a single polypeptide chain of 248 amino acids which is arranged in seven transmembrane α‐helices. A retinal molecule bound via a Schiff base to lysine‐216 forms the chromophoric group [3]. Under illumination BR creates a proton gradient across the cell membrane which is used by a membrane‐bound ATP‐ase for ATP syn

ISSN:0258-0322    

DOI:10.1002/masy.19910500111

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractIn this contribution the state‐of‐the‐art of ceramic‐matrix composites is briefly summarized. A critical review of the different types of ceramic composites is given, particularly emphasizing the challenge to chemistry. As example two important problem areas, which may only be solved by contributions from chemistry, are discussed: some low‐ temperature processing techniques for ceramic composites which avoid damage of fibres by thermal or mechanical loading and/or by chemical reactions as well as the optimization and control of i

ISSN:0258-0322    

DOI:10.1002/masy.19910500112

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY