Study on the Crystallization Behavior of Polymer Thin Films with a Substrate by Computer Simulation

The dynamics of polymers in ultrathin films can be significantly altered by the substrate interfaces. However, our understanding of how this depends on the film thickness and interface interaction is not mature. Here, the thin film is restricted on the substrate, and the effects of confined structure and interface interaction on crystallization are investigated by using dynamic Monte Carlo simulations. With the decrease in thin film thickness, the crystallization rate of the polymer film system increases gradually due to the enhancement of heterogeneous nucleation effect and the decrease in conformational entropy caused by the increase in chain deformation. Properly increasing the polymer-substrate interactions can reduce the surface free energy of the crystal nucleus. However, when the polymer-substrate interaction is too strong, an irreversible adsorption layer exists that inhibits the occurrence of heterogeneous nucleation. Simulation results verify some experimental phenomena (for instance, crystallization rate and crystal orientation) and observe the evolution process of the microstructure, which cannot be observed in the experiment. Our findings are helpful for the preparation and design of high-performance ultrathin films in experiment and industrial production.