Synthesis and characterization of liquid crystalline polymethacrylates, polyacrylates, and polysiloxanes containing 4-hydroxy-4'-methoxy-.alpha.-methylstilbene based mesogenic groups

The synthesis and characterization of polymethacrylates and polyacrylates containing 4-hydroxy-4'-methoxy- alpha -methylstilbene side groups attached through flexible spacers containing 11, 8, 6, 3, and 2 methylenic units and of the polysiloxanes containing the same mesogenic group connected through flexible spacers containing 11, 8, 6, and 3 methylenic units, respectively, are described. All polymers exhibit thermotropic liquid crystallinity. The nature of the mesophase is determined by the spacer length. However, the nature of the polymer backbone determines the thermal stability of the mesophase and the ease of the side-chain crystallization. That is, for the same spacer length and similar polymer molecular weight, the most flexible polymer backbone leads to the highest isotropization temperature and the highest ease of side-chain crystallization. This last effect may lead to transformation of enantiotropic mesophases into monotropic mesophases. Graph. 23 ref.--AA