Determination of the optical anisotropy of atactic polystyrene using a grating monochromator

To extract the intrinsic molecular scattering from unwanted collision‐induced contributions as much as possible we propose a simple useful method recording the depolarized Rayleigh spectra using a double grating monochromator and correcting the spectra for the high‐frequency wings. For this purpose we tested the system polystyrene/CCl 4 for which an asymptotic value of the optical anisotropy 〈γ 2 〉/ x ≅ 30 Å 6 with degree of polymerization x > 20 was found. The depolarized Rayleigh intensity of 2,4‐diphenylpentane and anionically polymerized atactic polystyrene standards was also measured in dilute solutions in the θ‐solvent bicyclohexyl (θ = 61°C). From the absolute depolarized Rayleigh ratio we obtained the configurational average optical anisotropy per number of monomer units, 〈γ 2 〉/ x . We have chosen cumene as a model compound estimating that its optical anisotropy is similar to that of a quasi monomer unit. No significant temperature dependence of 〈γ 2 〉/ x and of the static internal pair correlation in the temperature range from 25°C up to 80°C was found.