摘要:

AbstractWe describe a hybrid Monte Carlo algorithm, combining molecular dynamics with the Monte Carlo method, applied to the simulation of polymer systems. It is shown that observables are independent of the discretization error, and the performance, i.e., autocorrelation times of observables, is analyzed. For a dense system representing a polyethylene melt, we present data for the pair distribution function and the mean square displacement of a chain in the bulk. We also investigate the possibility of using a scaled Hamiltonian in the algorithm.

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020301

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA uniform star‐branched polymer model withf= 3 arms based on a simple cubic lattice was studied by means of the dynamic Monte Carlo method. The model chain is athermal with excluded‐volume interactions and it is flexible. A new type of local micromodification was introduced to make the branching point movable. Static properties of the star polymer are in accordance with other theoretical predictions and experimental evidence. Scaling of the self diffusion constant and the terminal relaxation times is close to those of the Rouse theory and to simulation results of linear cha

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020302

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractAnalytical results are presented for the mean‐square dimensions of star‐branched nonreversal random walk polymers on a tetrahedral lattice considering short‐chain effects and the influence of the core (centre) of the star. They are checked against numerical results obtained from highly precise Monte Carlo calculations. Short‐chain effects are studied in detail. In addition, the deviation from proportionality between mean‐square dimensions and the total chain‐length is evaluated and compared to that for self‐avoiding chains and stars near theta‐conditions, the total chain‐lengths ranging from 125

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020303

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA liquid crystalline system consisting of cyclic penta(methylsiloxane) cores with biphenylyl 4‐propoxybenzoate mesogens is studied with respect to its molecular conformation and the intermolecular ordering of pendant groups by employing molecular mechaincs calculations, while a molecular dynamics simulation indicates the degree of conformational flexibility. The calculated X‐ray scattering patterns for these structures provide insight into the origin of the experimentally observed results. A good agreement is found between the calculated and experimental reflections data, supporting the ‘cylinder’ global topology as the basis for forming a ‘columnar’ structure. Further, a comparison of the calculated and experimental meriodional sections shows a strong similarity of both the meridional intensities an

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020304

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe time evolution of the static structure factor following a sudden temperature jump ΔTis investigated in the case of a symmetric mixture of two polymers and a solvent in the optical theta conditions. The two reverse processes corresponding to ΔT>0 and ΔT<0 are considered, and the kinetics of approach towards the final states are investigated both in the Rouse limit and in the presence of hydrodynamic interactio

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020305

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe formation of polymer networks (gelation process) was studied by a numerical simulation of a lattice spin model with 3 states, which allows the representation of simple diffusion and aggregation processes. Near the percolation threshold,pc, the same critical exponents were detected as in the usual diffusion‐free classical percolation theory. Only non‐universal values (for examplepc) show a significant dependence on the ratio between diffusion and reaction consta

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020306

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractBy means of probability theory, the sol fraction of an Aa1Bb1−Aa2Bb2type copolymerisation reaction, in which intramolecular reactions are neglected, is investigated in the post‐gel regime to give the gelation condition explicitly. (Aa1Bb1is a monomer witha1functional groups of type A andb1functional groups of type

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020307

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe loosely cross‐linked poly(acryloyl‐L‐proline methyl ester) gel, which is known as one of the typical thermo‐responsive gels, shows a volume transition around approximately 14°C in pure water. This volume transition is shifted to higher temperature by treatment in aqueous sodium dodecyl sulfate (SDS). The analysis of the swelling‐temperature curve (frequency distribution) was performed according to a moment analysis, in which the area under the swelling‐temperature curve (AUC), mean swelling transition temperature (MSTT) and variance of swelling transition temperature (VSTT) were calculated. It is shown that the apparent volume transition temperature can be estimated from MSTT and that VSTT can be used to characterize the shape of the correspo

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020308

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA new method is presented for data reconciliation in the13C NMR determination of the pentad distribution in regioregular poly(propylene). Deviations of experimentally measured data from mathematically derived conservation laws are corrected by a maximum‐likelihood method. In this method some assumptions are made about the structure of the erros to obtain better estimates of the correct data. The validity of this procedure was demonstrated with Monte Carlo simulation, after which the method has been applied to real13C NMR data to show what corrections may be obtained. Conservation laws for hexads and heptads are derived as well, for possible future us

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020309

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPossible propagation mechanisms in propene polymerization using heterogeneous catalysts are described by combinations of Bernoulli and first‐ or even second‐order Markov models. Both NMR‐measured pentad fractions and GPCGel permeation chromatography.‐measured molecular weight distributions are directly taken into account to fit an appropriate propagation model for a specific catalyst. The analytical data so obtained have been used for an examination of the applicability of multi‐site propagation models and for estimation of the main parameters in each model. The propagation and termination probabilities are estimated, as are “mix” parameters giving the fraction of the polymer population stemming from each kind of propagation mechanism. In this way the subpopulation produced by each site is characterized in terms of tacticity and molecular weight distribution. A three‐site model is required to explain the measure

ISSN:1022-1344    

DOI:10.1002/mats.1993.040020310

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY