Morphology and Melting of Truncated Single Crystals of Linear Polyethylene

Abstract

The thickness of (110) and (200) sectors in truncated single crystals of linear polyethylene grown from dilute n-octane solution at 95 °C was measured by atomic force microscopy (AFM) in tapping mode. The (110) sector was found to be 1.1 nm thicker than the (200) sector. This can be explained by a somewhat smaller tilt angle of the chains with respect to the basal plane of the crystal. The tilt of the chains in (110) and (200) sectors, obtained by electron diffraction, is 22° and 30°, respectively. This implies that the length of the stem, i.e., the length of the straight part of the chains between two consecutive folds, is identical in both sectors of the truncated single crystals. The melting of individual LPE truncated single crystals was revisited by AFM. The melting temperatures of the (200) and (110) sectors are 124.9 and 125.9 ± 0.3 °C, respectively. The lamellar thickness distribution calculated from AFM pictures clearly indicates that reorganization into thicker lamellae takes place during heatin...