Optical anisotropy of linear and star polyisoprene by depolarized Rayleigh scattering

The absolute depolarized intensity R _VH for linear and 12-arm star polyisoprene (PI) for a number of molecular weights and concentrations in CCl ₄ has been obtained from the depolarized Rayleigh spectra recorded with a plane Fabry-Perot interferometer. The effective optical anisotropy <γ ²>/x(=10.4±0.8 angstrom ⁶) per monomer unit is virtually independent of concentration and molecular weight and is comparable to be optical anisotropy β ² of the monomer unit calculated from the molecular geometry and bond anisotropies. The weak internal orientation correlations are consistent with a strain-birefringence data and rotational isomeric state model calculations for linear PI. Core effects are very weak for the 12-arm star PI considered here.