Temperature-induced pattern transition in crystallizing ultrathin polymer films

The crystallization patterns of ultrathin poly(ethylene oxide)/poly(methyl methacrylate)(PEO/PMMA) blend films crystallized at different undercooling were investigated by atomic force microscopy. Dendrite pattern formed as a result of crystalline anisotropy at low undercooling and evolved into seaweed pattern with increasing undercooling. Although the configuration of macromolecules is far different from that of simple small molecules, the crystallization pattern transition in ultrathin polymer films can be interpreted by the classical morphology diagram developed on the basis of metals and simple molecules, indicating that polymer chains can be considered as simple dynamical units in a quasi-two-dimensional confined state.