Crystal growth of isotactic polystyrene in ultrathin films: Thickness and temperature dependence

摘要

The growth rate and morphology of isotactic polystyrene crystals grown in ultrathin films have been examined experimentally in terms of the dependences both on the film thickness and on the crystallization temperature. We have found that the thickness dependence of growth rate, G, shows a crossover change when the film thickness becomes comparable with the lamellar thickness of the polymer crystals, irrespective of the temperatures. The morphology of crystals grown in ultrathin films shows a branching typical of dendrites, the growth of which is supposed to be controlled by a diffusion field. The change in the tip width of the dendrites with crystallization temperature follows the expected dependence of the Mullins-Sekerka stability length, l(MS) proportional to (D/G)(1/2), determined by the diffusion coefficient, D, and the growth rate. The results confirm that a diffusion field plays an essential role in the evolution of the structure.