Entropic Barrier Theory of Polymer Melting and Energy Cascade

We will present a theory of melting kinetics of semicrystalline polymers at temperatures above the equilibrium melting temperature, by accounting for conformational entropy of chains during melting and the characteristics of lamellae. We show that melting of lamellae is always accompanied by a free energy barrier which is entirely entropic in origin. In terms of the parameters characterizing the lamellae and the extent of superheating, closed-form formulas will be presented for the equilibrium melting temperature, driving force for crystallization, free energy barrier height, average expulsion time of a single chain from a lamella, and the melting velocity of lamellae. The predicted dependence of melting velocity on superheating is nonlinear and non-Arrhenius, in qualitative agreement with experimental observations reported in the literature. In addition, the cascade of dissipation of injected energy into semicrystalline polymers will be addressed.