Morphology and Crystallization Kinetics of it-Polystyrene Spherulites

作者：Kajioka Hiroshi; Yoshimoto Shigeru; Taguchi Ken; Toda Akihiko^*

来源：Macromolecules, 2010, 43(8): 3837-3843.

DOI：10.1021/ma9028486

Based on our recent proposal for the formation mechanism of polymer spherulites, the correlation between the morphology and crystallization kinetics has been examined for it-polystyrene (itPS) spherulites grown from the melt down to temperatures near the glass transition, T(g). The inner structure of the nonbanded spherulites of itPS has been characterized by the persistence length of the patchy pattern observed by polarizing optical microscopy. The persistence length was in proportion to the width of lamellar crystals at the growth front, which was observed by atomic force microscopy. The result reconfirms our suggestion that the inner structure of spherulites is determined by the size of the building blocks. For the determination mechanism of the width of lamellae, the possibility of instability-driven branching has been examined by the correlation between the characteristic lengths and the growth rate in terms of the temperature dependence near T(g). The correlation followed the dependence predicted for the two cases of the instability caused by the compositional gradient and by the pressure gradient. The compositional gradient is determined by the self-diffusion of polymer chains and the pressure gradient by the melt viscosity. Near T(g), owing to the development of spatial heterogeneity, the decoupling of self-diffusion from the melt viscosity can be expected. By examining the possible decoupling, the cases were dismissed for the influence of self-diffusion of portions of polymer chain on crystallization at the growth front and for the compositional gradient formed by small uncrystallized molecules.

• 出版日期2010-4-27