Computer simulation of the dynamics of highly entangled star polymers

Abstract

A computer model for the simulation of the dynamics of highly entangled polymers, previously used to study the behaviour of linear chains, is adapted to examine the behaviour of star polymers. It is shown that the relaxation time of the star molecule T_s∝N⁴, where N is the number of segments in the chain, and the diffusion constant of the whole chain D_s∝N^–3. Experimental work by several authors on the viscosity of star-branched polystyrene is shown to be in reasonable agreement with this molecular weight dependence of the relaxation time. The assumption that the mid-point of the star molecule is effectively fixed while the arms relax, which is the basis of recent theoretical models predicting η∝ exp (aN), where η is the viscosity and a is a constant, is shown to be erroneous.