Temperature and Gradient-Induced Segregation in Polymer Mixture via Crystallization: MD Simulations

Temperature gradients exert a significant influence on both the growth direction and the growth rate of polymer crystals. However, the molecular-level details of polymer crystallization under such conditions have not yet been fully clarified. We studied the nucleation and growth processes of polymer pure systems (uniform chain length and topology) and mixed systems (mixtures of linear chains of varying lengths or cyclic and linear chains) under temperature gradients by using coarse-grained molecular dynamics simulations. The simulation results show that the interface between the crystalline and molten regions happens in the region where the degree of supercooling is lower; i.e., the crystallization temperature is close to the melting temperature. Crystallization results in the segregation of different components in mixed systems along the growth direction. The segregation effect is governed by the crystal growth rate and component differences, including chain topology and length. This study uncovers the molecular-level crystallization behavior of polymers under temperature gradients, offering new insights into the segregation and purification of polymer mixtures.