What Determines the Lamellar Orientation on Substrates?

Abstract

The recrystallization behavior of poly(ethylene oxide) (PEO) on four amorphous films of poly(vinyl alcohol) (PVA), lysozyme (LYSO), poly(vinylpyrrolidone) (PVPY), and poly(acrylic acid) (PAA) was investigated using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The results show that both the degree of supercooling and PEO/substrate interactions have pronounced influence over the growth behavior of the PEO crystals. A thermodynamic model has been proposed accordingly, in which the lamellar orientation is associated with the favorite primary nucleation. We predict the lamellar orientation based on the degree of supercooling and the surface free energy of substrate. The transition of lamellar orientation from edge-on to flat-on is determined by a critical surface free energy of the substrate which is equal to the surface tension of the polymer melt.