The effect of grafting density on the crystallization behavior of one-dimensional confined polymers

Grafting density and confinement scale of the nano-area are significant elements affecting the crystallization behavior of polymers. In this work, the crystallization processes of confined and unconfined polymer systems with different grafting density were systematically studied by MC simulation. The results show that when the grafting density of confined systems is low, the crystallization rate is faster and the final crystallinity is higher. However, the crystallization ability is reduced for higher grafting density. We found that for this confined system, the segmental density of interfacial region is larger, and the movement of chain segment is lower. Due to the higher grafting density, the crowding effect of polymer chains is strong, which leads to the intermolecular nucleation. The critical nucleation free energy barrier is higher. Moreover, only homogeneous nucleation occurs in confined polymer systems. With the increasing grafting density, the crystals change from lying on the substrate surface to being perpendicular to the substrate surface in unconfined polymer systems. The crystals are mainly lying on the substrate surface in confined polymer systems. These simulation results are helpful to understand the microscopic mechanism of crystallization behaviors of polymer nanocomposites and provide a theoretical basis for the design of nanocomposites with excellent physical properties.