Insights into the crystallization behavior of structurally and spatially doubly confined polymer systems studied by molecular simulation

The impact of grafting density and polymer-substrate interactions on the crystallization behavior of structurally and spatially doubly confined polymer systems was studied using Monte Carlo simulation methods. In the confined polymer system with low grafting density, as the polymer-substrate interactions increase, the nucleation mode shifts from homogeneous nucleation to heterogeneous nucleation. The melting temperature and undercooling increase, while the critical nucleation free energy barrier decreases, favoring the crystallization process. Nevertheless, significant polymer-substrate interactions can lead to a decrease in the mobility of polymer chains, thereby inhibiting the crystallization process. In highly grafted polymer systems, homogeneous nucleation controls the entire crystallization process and the crystallization rate and final degree of crystallinity are almost unaffected by polymer-substrate interactions. Grafting density and polymer-substrate interactions play a dual role, acting as a “double-edged sword” in the crystallization process of doubly confined polymer systems. An appropriate grafting density and polymer-substrate interactions facilitate the nucleation ability, thereby promoting the crystallization capability of polymer systems. Conversely, excessive interactions can weaken nucleation ability and suppress crystal growth.