摘要:

AbstractThe theory of polymer melts is founded on the process of double reptation for high masses and long times, and on simple Rouse relaxation for low maases and short times. In order to describe the intermediate region, these two different principles have to be combined, and we show how this can be done. However, pure reptation is modified under the influence of an effect which cannot be reduced to the Rouse elasticity of polymers, and this effect could be calculated by mode‐mode couplin

ISSN:1022-1360    

DOI:10.1002/masy.19940810103

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWe discuss statics and dynamics of an excluded volume polymer moving in a Gaussian distributed random one body potential. Stressing the intimate connection of universality and renormalizability we point out which features can be expected to be universal. We in particular note that universality holds only as long as the excluded volume in some sense dominates over disorder. Whereas universal static properties up to a trivial redefinition of the excluded volume interaction coincide with those found for the standard excluded volume problem, we find highly nontrivial results for universal dynamic quantities. We in particular discuss our recent results on the center of mass motion.

ISSN:1022-1360    

DOI:10.1002/masy.19940810104

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractFor polymer dynamics in quenched random media a renormalizability proof is lacking and calculations are lengthy. We here propose and define the static and the ergodic limit of the dynamic theory, and show, that these limits are equivalent to well‐known renormalizable static polymer theories. This procedure supplies us with a renormalizable substructure and puts the 2 loop analysis of the full theory within reac

ISSN:1022-1360    

DOI:10.1002/masy.19940810105

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe non‐Markovian dynamics of a macromolecule in a nematic viscoelastic liquid is studie

ISSN:1022-1360    

DOI:10.1002/masy.19940810106

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe cooperativity of conformational transitions in strained linear polymer chain was investigated by the method of Brownian dynamics. Deformation of a chain consisting of N=32 and 64 bonds was created by strong external field of dipole type. Correlations are discussed in terms of hazard‐plot analysi

ISSN:1022-1360    

DOI:10.1002/masy.19940810107

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper presents some results of a Monte Carlo simulation for the glass transition in two‐ and three‐dimensional polymer melts. The melt was simulated by the bond‐fluctuation model on ad‐dimensional cubic lattice which was combined with a two‐level hamiltonian favouring long bonds in order to generate a competition between the energetic and topological constraints in the system. This competition prevents crystallization and makes the melt freeze in an amorphous structure as soon as the internal relaxation times match the observation time of the simulation set by the cooling rate. The freezing point of the melt, i.e the glass transition temperatureTg, thus depends upon the cooling rate and additionally upon the chain length of the polymers. The dependence of the glass transition temperature on the cooling rate was closely analysed in three and that on the chain length in both two and three dimensions, resulting in a non‐linear relationship betweenTgand the logarithm of the cooling rate and a linear relationship betweenTgand the inverse chain length, respectively. In addition to this behaviour of the melt during the cooling process an example for the relaxational properties of the three‐dimensional model is provided by a quantitative analysis of the incoherent intermediate scattering function in the framework of the idealized mode co

ISSN:1022-1360    

DOI:10.1002/masy.19940810108

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractGlass transition temperatures Tg in a series of 24 linear polymers with different chemical structure and high molecular weight beyond entanglement limit are correlated in the framework of freely jointed chain model with the statistical characteristics of chain parts between entanglements.

ISSN:1022-1360    

DOI:10.1002/masy.19940810109

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe single‐link orientational distribution function and the space‐averaged stresses in the fluid are computed for the case of steady shear flow of polymer melts. The computation is achieved with Galerkin's method with spherical harmonics and Euler polynomials as trial functions. The stress components become power functions of shear rate when the latter is large. The single‐link orientational distribution functionfsolves the Fokker‐Planck equation subject to a boundary condition forfat the chain ends. A solution is obtained for every shear rate and ratio of the orientational and one‐dimensional diffusion coefficient. It is demonstrated that the Fokker‐Planck equation with appropriate boundary condition is useful in order to predict the flow‐alignment and stresses in good agreement with experimental data as well as with recent results of a nonequilibrium molecular dynamics computer simulation on

ISSN:1022-1360    

DOI:10.1002/masy.19940810110

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWe present a novel analytically tractable model for stiff chain molecules. The equilibrium distribution function of the chain is derived using the maximum‐entropy principle. For that purpose, we first formulate a discrete chain model, where the connections of the points and the restriction on bending are taken into account via constraints. We then perform the limit to a continuous chain and show that the mean‐square end‐to‐end distance and the radius of gyration of the continuous chain are identical with the same quantities of the Kratky‐Porod wormlike chain. The dynamics of our chain is investigated in dilute solution without hydrodynamic interactions. The linear dynamical equation is solved by a normal mode analysis. We discuss the dependence of the relaxation times on the single parameter of the model, the persistence length. For small persistence lengths we obtain the well known relaxation times of the Rouse model. In the stiff‐chain limit, we find the pure bending relaxation times and, in addition, the rotational rela

ISSN:1022-1360    

DOI:10.1002/masy.19940810111

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWe consider DNA gel electrophoresis in the framework of the lakes‐straits model, proposed by Zimm in Phys. Rev. Lett.61, 2965 (1988) and J. Chem. Phys.94, 2187 (1889). Here we evaluate the tension on a Gaussian chain‐fragment confined in a lake, by accounting for its variable length. Through numerical simulations we find that the precise form of the tension is very important for the calculation of the absolute value of the mobility of the chain and that it is of minor importance for establishing the frequency‐dependence of the mob

ISSN:1022-1360    

DOI:10.1002/masy.19940810112

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY