Polymer Melt Viscosity

TL;DR

This paper explores the molecular theory of polymer melt viscosity, deriving a power law relation with the molecular weight within the reptation model, and emphasizes the importance of chain end motions for accurate exponent estimation.

Contribution

It introduces a refined theoretical approach that accounts for chain end motions to better match experimental viscosity exponents in polymer melts.

Findings

Reptation model predicts a 3.5 power law for viscosity versus molecular weight.

Chain end rotation vibrations influence the viscosity exponent.

Inclusion of chain end motions improves agreement with experimental data.

Abstract

The research is important for a molecular theory of liquid and has a wide interest as an example solving the problem when dynamic parameters of systems can be indirectly connected with their equilibrium properties. In frameworks of the reptation model the power law with the 3.5-exponent for the melt viscosity relation to the molecular weight of flexible-chain polymer is obtained. In order to find the exponent close to experimental values it should be taken into account the rotation vibration precession motion of chain ends with respect to the polymer melt flow direction.