Novel analysis of static light scattering data

Abstract

A novel analysis was carried out for static light scattering data to determine the molecular weight, M, and mean square radius of gyration 〈 s 2〉 of large molecular weight polymers. The analysis is based on the finding that the Debye scattering function P( x) for random flight polymer chains with x = (4 πn/ λ) 2 〈 s 2〉 sin 2 ( θ/2) can be numerically approximated by the single term (1 + x/3 a) − a with the exponent a near 1.5, where λ/ n is the wavelength of incident light in medium and θ is the scattering angle. The ratio (1 + x/3 a)/ P( x) −1/ a changes slowly between 0.986 and 1.014 in the range x < 8.6 for a = 1.5 and between 0.972 and 1.028 in x < 14.5 for a = 1.4. The plots of P( θ) −1/ a vs sin 2(θ/2) with a = 1.4 and 1.5 were applied successfully to various light scattering data on polymers of large molecular weight more than several million yielding the intercept of unity and correct values of 〈 s 2〉.