ON THE MELTING-POINT DEPRESSION OF COPOLYMER CRYSTALS

The melting-point depression of a random copolymer with comonomer exclusion from the crystalline phase is investigated. The analysis is based on simulation results obtained with an extended Sadler-Gilmer crystallization model. Apparent copolymer melting points T(m)cop(l) of lamellae of finite thickness l are observed. Further thickening is entropically suppressed. It is shown that the average lamellar thickness and the minimum thermodynamically stable thickness converge at T(m)cop. The fine-grained nature of the model reveals an entropic contribution to the melting-point depression, which is due to the so-called blind attachment of chain segments to the growth face. Our new 'kinetic' melting-point equation is compared with the 'equilibrium' result by Flory and shows a considerably stronger melting-point depression.