Conformational statistics of polymer chains in the interphase of semi-crystalline polymers

Abstract

The microscopic structure of a semi-crystalline polymer interphase has been investigated by off-lattice Monte Carlo techniques for polyethylene-like flexible chains. In this approach, the conformational space consisting of chain populations of loops, bridges and tails is explored by robust cutting and splicing moves in real space. The simulations capture the most probable equilibrium distributions. The populations of loops and tails follow a truncated exponential distribution and the population of bridges shows a maximum as a function of chain length. For simulations of flexible chains, 40–45% of the chains form adjacent entry folds. The effect of molecular weight has been investigated. The bridge population is found to increase from 5 to 10%, for the interphase thicknesses studied, as the molecular weight of material simulated increases from ∼8000 gm/gmol to ∼30 000 gm/gmol. A Gaussian model for the interphase has been developed and compared with simulations of non-interacting phantom chains. The distributions match well at long chain lengths and deviate at short lengths.