Hydrodynamic properties and optical anisotropy of molecules of linear and cyclolinear polyphenylsiloxanes in solution

Some fractions of cyclolinear polyphenylsiloxanes (ladder polymer) were investigated by flow birefringence, diffusion, and sedimentation in solution. By the same methods were investigated some samples of linear polymethylphenylsiloxanes (MPhS), which differ one from another by degree and order of substitution of methyl groups on phenyl ones. The experimental data obtained were used for the determination of the optical anisotropy and rigidity of the polymer molecules. The negative segmental anisotropy of MPhS molecules is increasing monotonically with degree of substitution by phenyl groups. Rotational hindrance of side phenyl radicals somewhat changes with degree and order of substitution, although flexibility of the backbone remains practically unchanged. Optical anisotropy of molecules of cyclolinear polyphenylsiloxane (CLPhS) is very high, which appears to be the result of great skeletal rigidity of the main double chain. Dependence of anisotropy and hydrodynamic characteristics upon molecular weight also indicates on great rigidity of CLPhS molecular chain. Dimensions of Kuhn's statistical segment for CLPhS molecules, determined from optical and hydrodynamic data, is one order higher than the values usually obtained for chain molecules of synthetic polymers.