Side-chain liquid crystal polymers. A study by neutron diffraction of the backbone distribution profile in the smectic A phase

Abstract

Two mesomorphic side-chain polymethacrylates, called PMA(R)OC₄H₉, and only differing in the fact that one was deuteriated on the backbone (R = D) have been studied by neutron diffraction in the smectic A phase. The comparison between their respective smectic reflection intensities allows one to deduce quantitatively the backbone distribution profile along the normal to the layers. As the temperature decreases, the polymer backbones are more and more segregated from the sublayers of mesogenic cores. However, even at room temperature, there are still about 25 per cent of the backbone segments localized in the mesogenic core sublayers. These measurements, together with the previous determinations of the gyration radii of the backbones provide a detailed description of how the backbones of PMAOC₄H₉ are affected by the smectic ordering. In addition, the evolution with temperature of the different smectic reflection intensities is also discussed.