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.