Systematic Control of Self-Seeding Crystallization Patterns of Poly(ethylene oxide) in Thin Films

Using optical microscopy and atomic force microscopy, we studied systematically crystallization patterns in thin films of a low molecular weight poly(ethylene oxide) (PEO) resulting from a kinetically controlled self-seeding approach. In particular, the influence of seeding temperature (Ts) and heating rate (Vh) on the various resulting crystallization patterns was investigated. Crystallization at 49 °C resulted in dendritic PEO crystals consisting of almost exclusively twice-folded chains. Upon heating these crystals, we observed crystal thickening due to a reduction in the average number of chain folds. On the basis of the detected morphology, we deduced that the density of seeded PEO crystals decreased when increasing Ts from 54 to 57 °C. At the highest Vh (i.e., 100 °C/min), only a few well-separated faceted single crystals of PEO were grown from individual seeds. In contrast to such random distribution of crystals, because of a faster reduction of chain folds at the edges of PEO lamellae, an almost c...