Shear-Induced Order in Nematic Polymers

Several nematic side-chain polysiloxanes with the same backbone and the same mesogens but containing various ratios of two spacers having different lengths were prepared. Within this series of homo- and copolymers, the phase behavior changes continuously from purely nematic for the homopolymer containing only the shorter of the two spacers to nematic plus smectic for the homopolymer containing only the longer spacer. The flow behavior determined by in situ deuterium NMR spectroscopy under shear and the anisotropy of the coil conformation measured by small angle neutron scattering exhibit a continuous change as well.