Side-Group Liquid Crystal Copolymers Containing Nonmesogenic Units: Dependence of the Thermal Behaviour upon Composition

The synthesis and properties of a new mesogenic/nonmesogenic copolymer system, namely the poly [6-(4'-methoxyazobenzene-4'-oxy)hexyl methacrylate]-co-poly[methyl methacry late]s, are described. Copolymers containing 0.59 or greater mol fraction of the mesogenic side-groups exhibit nematic behaviour while those containing 0.39 or less mol fraction mesogen are amorphous. The glass transition temperatures exhibit a negative deviation from linear behaviour on varying the copolymer composition. In contrast, the nematic-isotropic transition temperatures decrease in an essentially linear fashion on increasing the nonmesogen content, This behaviour is compared with that of a smectogenic series and differences are accounted for in terms of a microphase separated smectic phase.