Structures and Phase Transitions of di-methyl, di-ethyl, and di-n-propyl Polysilylenes

In view of the 7/3-helical conformations of the di-n-pentyl and di-n-buty and di-n-butyl polysilylenes and of a diversity of results from energy calculations, we became interested in the structures of the lower homologues. Using X-ray and electron-diffraction analyses on uniaxially oriented specimens, we found that di-n-propyl, diethyl, and di-methyl polysilylenes all adopt trans conformations. The interchain packing was determined from electron microscopy and diffraction of solution-grown single crystals of these three polymers, whose morphology will be described.