MICROSCOPIC THEORY OF CHAIN PULLOUT IN AMORPHOUS POLYMERS

The statistical-mechanical problem of chain pullout from an amorphous polymer under the influence of a constant force has been investigated. A simple microscopic model is proposed to describe the pullout proces s in both polymer glasses and elastomeric materials from a single poin t of view. A mean-field approximation for the interchain potential is used to account for the entanglements with the polymer network of the chain being pulled out. The chain mobility and the pullout rate were c alculated as a function of pullout force, length of the chain, and oth er model parameters. In glassy polymers the pullout force was found to be almost rate independent at low pullout rates and linear in rate at high pullout rates. For polymer glasses the model also predicts the e xistence of some characteristic degree of polymerization N-e of the ch ain being pulled out, such that the pullout force scales as N for N mu ch less than N-e but as N-3 for N much greater than N-e. In elastomeri c materials the pullout force was found to have a nonlinear dependence on both chain length and rate of pullout.