Influence of the length of side substituents on optical and electro-optical properties of polydialkoxyphosphazenes

The electro-optical and dynamo-optical properties of dilute solutions of polydialkoxyphosphazenes with different lengths of side substituents are studied. Sign inversion of the specific Kerr constant and of the reduced flow birefringence for the number of carbon atoms in side aliphatic chains, m, varying from 3 to 7 is ascertained. The anisotropy of optical polarizability of a monomer unit changes in the studied series of polydialkoxyphosphazenes. It attains the minimum values and changes its sign from positive to negative at m = 5-6. The resulting data provide an explanation for the mesomorphism of these polydialkoxyphosphazenes, which is connected with the possibility of alternative orientation of monomer units.