Study of smectic layer liquid crystal formed by rod-like polymers arranged their molecular terminals regularly in space

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Polysilanes having optically active side-chain exhibit rod-like configuration. They forms clear thermotropic-cholesteric liquid crystal when their molecular weights are relatively small, while they show smectic phase under cholesteric liquid crystal phase when molecular weight distribution is narrow (Mw/Mn < 1.1) and their smectic layer distance corresponds to the molecular length of polysilane. In this study, we mixed two samples with different molecular weights to observe behavior of smectic layers. As a result, we found that smectic phase is unstable when difference of the molecular weights is small, while two smectic phase is separated when difference of the molecular weights is large.Additionally, we prepared a diblock copolymer composed of polystyrene (PS) and side-chain liquid crystal polymer (LCP) by atom transfer radical polymerization. The weight fraction of the PS segment is 0.22, resulting in a microsegregated structure with PS cylinders hexagonally packed in a matrix of LCP, which forms smectic A, nematic and isotropic phases in order of increasing temperature. Shear flow at nematic temperatures orients well the PS microcylinders, as well as the nematic mesogens of the LCP in the velocity direction. A high degree of orientation of 0.95 is attained for microcylinders while the orientational order parameter of the nematic LC is around 0.5. Interestingly, the nematic LC mesogens recover their initial orientation upon cooling after they have lost the orientational order in the isotropic melt. This spontaneous orientation shows that PS cylinders whose orientation is strongly sustained with a temperature variation acts as an anchoring substrate for the nematic mesogens.