An X-Ray Diffraction Study on Crystalline and Mesomorphic Structures of Poly(diethylsiloxane)

Abstract

Crystal structure and molecular packing analysis for crystalline and mesomorphic poly(diethylsiloxane) (PDES) have been studied by wide-angle X-Ray diffraction measurements using uniaxially-oriented PDES sample without crosslinking process. Well-oriented fiber diffraction pattern measured at 0°C, which corresponds to the β2 polymorph, can be satisfactorily indexed by monoclinic unit cell with c (fiber axis)=5.02A. Only four independent reflections can be observed for mesomorphic PDES at 26°C, but the orientational direction of the PDES specimen has been maintained after the crystalline-mesophase transition. Molecular-packing manner of crystalline β2-PDES has been estimated with assuming planar-Si-O-backbone with alternating cis-trans conformation.