Polymer-Mode-Coupling Theory of Finite-Size-Fluctuation Effects in Entangled Solutions, Melts and Gels. II. Comparison with Experiment

TL;DR

This paper tests polymer mode coupling theory against experimental data for entangled polymer systems, successfully explaining transport properties and anomalous scaling behaviors through finite size corrections and structural parameters.

Contribution

It provides a quantitative comparison of the theory with experiments, introducing a microscopic structural fit parameter and explaining complex scaling behaviors in entangled polymers.

Findings

Quantitative agreement with experimental viscosities, relaxation times, and diffusion coefficients.

Finite size corrections and constraint porosity explain power law behaviors.

Theory extends to polymer diffusion in gels, explaining high molecular weight scaling anomalies.

Abstract

The predictions of the polymer mode coupling theory for the finite size corrections to the transport coefficients of entangled polymeric systems are tested in comparisons with various experimental data. It is found that quantitative descriptions of the viscosities, eta, dielectric relaxation time, tau_e, and diffusion coefficients, D, of polymer melts can be achieved with two microscopic structural fit parameters whose values are in the range expected from independent theoretical or experimental information. An explanation for the (apparent) power law behaviors of eta, taue, and D in (chemically distinct) melts for intermediate molecular weights as arising from finite size corrections, mainly the self-consistent constraint release mechanism, is given. The variation of tracer dielectric relaxation times from Rouse to reptation-like behavior upon changes of the matrix molecular weight is analyzed. Self and tracer diffusion constants of entangled polymer solutions can be explained by the theory as well, if one further parameter of the theory is adjusted. The anomalous scaling of the tracer diffusion coefficients in semidilute and concentrated polystyrene solutions, D\sim N^{-2.5}, is predicted to arise due to the spatial correlations of the entanglement constraints, termed ``constraint porosity''. Extensions of the theory to polymer tracer diffusion through polyvinylmethylether and polyacrylamide gels provide an explanation of the observation of anomalously high molecular weight scaling exponents in a range where the size of the tracer, R_g, already considerably exceeds the gel pore size, xi_g.