SYNTHESIS AND CHARACTERIZATION OF LIQUID-CRYSTALLINE POLYSILOXANES WITH 2-CHAIN DIOL UNITS IN THE SIDE-CHAIN

The synthesis and the thermal behaviour of different polysiloxanes containing cis,cis-(3,5-dihydroxycyclohexyl) 3,4-bis(alkoxy)benzoate mesogens (''two-chain'' diol unit) in the side chain are described. Aggregation via intermolecular hydrogen bonding between different ''two-chain'' diol units leads to the formation of mesomorphic supramolecular structures. The phase behaviour changes drastically by variation of the dimethylsiloxane content of the backbone. Thus, the homopolysiloxane is the first example of a polymer with a thermotropic cubic mesophase, being observed below a hexagonal columnar one. However, the copolymers exclusively form the hexagonal columnar mesophase. The thermal transitions of all polymers, investigated by means of differential scanning calorimetry (DSC) as well as by polarizing microscopy, are discussed. The mesophase structures have been determined by X-ray measurements in combination with miscibility studies.