Communication: Theory of melt-memory in polymer crystallization

Details of crystallization processes of a polymer at the crystallization temperature T-c from its melt kept initially at the melt temperature T-m depend profoundly on the nature of the initial melt state and often are accompanied by memory effects. This phenomenon is in contrast to small molecular systems where the supercooling (T-m(0)-T-c), with T-m(0) being the equilibrium melting temperature, and not (T-m-T-c), determines the nature of crystallization. In addressing this five-decade old puzzle of melt-memory in polymer crystallization, we present a theory to describe melt-memory effects, by invoking an intermediate inhomogeneous melt state in the pathway between the melt and crystalline states. Using newly introduced dissolution temperature T-1(0) for the inhomogeneous melt state and the transition temperature T-t(0) for the transition between the inhomogeneous melt and crystalline states, analytical formulas are derived for the nucleation rate as a function of the melt temperature. The theory is general to address different kinds of melt-memory effects depending on whether T-m is higher or lower than T-m(0). The derived results are in qualitative agreement with known experimental data, while making predictions for further experiments on melt-memory. Published by AIP Publishing.