How the restriction of sliding diffusion of comonomers affects crystallization and melting of homogeneous copolymers

In ethylene-based copolymers, large comonomers/branches make the sliding diffusion difficult in the crystalline regions constituted by small monomers. We studied the influence of such a restricted sliding diffusion on the mechanisms of crystallization and melting of homogeneous copolymers, by means of dynamic Monte Carlo simulations. Comparing two extreme cases—no restriction and a hard restriction—we found that the hard restriction increases both temperatures of crystallization and melting on the temperature scanning. Moreover, during crystallization, the restriction weakens segregation of sequence lengths and decreases the lamellar-crystal thickness. These results can be attributed to a switch of the dominant crystal growth mode from longitudinal thickening to lateral growth due to the presence of a hard restriction.