SURFACE-MORPHOLOGY OF SYNDIOTACTIC POLYPROPYLENE SINGLE-CRYSTALS OBSERVED BY ATOMIC-FORCE MICROSCOPY

We have studied the surface morphology of single crystals of syndiotac tic polypropylene (sPP) by atomic force microscopy (AFM). The thicknes s of a single crystal lath grown at 140 degrees C was determined by AF M to be 10.5 +/- 1 nm. The surface roughness within nat, defect-free a reas up to 1 mu m across was in the range 0.3-1 nm. A feature of the s PP single crystals was straight cracks about 100 nm wide across the si ngle crystal laths. Three to four cracks were observed on a single-cry stal with the average distance between adjacent cracks of 5-10 mu m. S mooth periodic undulations in thickness, or wrinkles, were observed. T he periodicity of these undulations is about 400 ma and the number of periods can reach 10-30. On the molecular scale, we observed modulatio ns of surface topography with periods of 1.5 and 1.1 nn that are close to the lengths of the a and b edges of the sPP unit cell determined f rom electron diffraction.