Morphology of Form I′ crystals of polybutene-1 formed on melt-crystallization

Abstract

It is known that presence of both constitutional chain defects and stereodefects in butene-1 macromolecules may lead to the formation of the trigonal Form-I′ crystal polymorph on cooling the melt. In this study, Form I′ crystals were prepared by slow cooling of the melt of a specific random copolymer of butene-1 containing about 18 mol% propylene, and analyzed for the first time regarding their morphology by atomic force microscopy. It has been found that Form I′ crystals which develop on slow cooling of the isotropic melt exhibit a lamellar crystal shape, with a thickness and lateral width of less than 10 and 500 nm, respectively. In addition, there was proven that at the particular crystallization conditions the lamellae form stacks. Though crystallization seems non-spherulitic, the irregularly oriented stacks of lamellae are then also detected by polarizing optical microscopy.