Direct determination of polymer crystal structures by electron crystallography – isotactic poly(1-butene), form (III)

Abstract

Three-dimensional electron diffraction intensity data from form (III) of isotactic poly(1-butene) have been collected by tilting solution- and epitaxially grown thin microcrystals. The orthorhombic space group is P2 1 2 1 2 1 with cell constants a= 12.38, b= 8.88 and c= 7.56 A, the latter being the chain repeat. The crystal structure was determined by direct methods, employing the tangent formula (QTAN) and initially 106 phase values were found for 125 unique observed reflections. Refinement by Fourier techniques gave a structure very similar to that proposed in an earlier powder X-ray diffraction study