Small-angle X-ray analysis of smectic a cholesteric liquid crystal phase transition in rigid-rod helical polysilane

摘要

The smectic A Cholesteric liquid crystal phase transition of rigid-rod helical polysilane was studied by means of synchrotron radiation small-angle X-ray scattering ( SR-SAXS). The information on the smectic trans-layer electron density distribution was clarified by fitting the model of electron density distribution to the diffraction data. Each of the layers was approximated by the boxlike function to introduce the molecular form factor of the polymer. The distribution of the molecular center of gravity within the layers due to the thermal motion was taken into consideration by convolution with the Gaussian function. The elucidated smectic layer structure was not like the conventional structure with their ends packed into the interlayer space. The layers with bumpy surfaces interdigitate in a key-and-keyhole manner to pack the molecules with different lengths into layers due to their finite molecular weight distribution.