LATTICE IMAGING IN MELT CRYSTALLIZED POLYPROPYLENE THIN-FILMS

Melt crystallized isotactic polypropylene thin films of thickness betw een 30 and 100 nm have been investigated by high-resolution transmissi on electron microscopy at roam temperature. The c-axis projection of t he 23(1) helices and their packing in the lattice were clearly visibl e in flat-on lamellae of the alpha-phase following reconstruction from the components of the image Fourier transform corresponding to the (1 10) and (040) lattice planes, and the image power spectra also indicat ed contributions from (130)and (060) relfections, corresponding to a l ine resolution of about 0.35 nm. These results are discussed in terms of Bloch wave calculations based on the generally accepted structure f or the alpha-phase. Attempts to obtain lattice images of the beta-phas e in isotactic polypropylene and melt crystallized syndiotactic polypr opylene under similar operating conditions are also briefly discussed, although these provided relatively little structural information.