Studies on light scattering by polymethyl methacrylate solutions

Abstract

The scattering of light by solutions of a well-fractionated sample of polymethyl methacrylate in acetone, methyl ethyl ketone, and benzene, have been measured using 4358 and 5461 A. wave lengths as incident radiations. The average molecular weights of the polymer from turbidity measurements and lengths determined from angular dissymmetries of scattered light are 571,000 and 760 A. in acetone, 38,400,000 and 715 A. in methyl ethyl ketone, and 408,000 and 375 A. in benzene. The abnormal molecular weight observed in methyl ethyl ketone solution may be ascribed to low µ - µ₀ value of the medium. The greater molecular extension in ketone than in benzene solutions is explained in terms of the relative magnitudes of solute-solvent interaction. The depolarization ratios ρu, ρv and ρh have been measured and the decrease of ρv and ρh with increase in concentration of the polymer in ketonic solvents and little change under similar conditions in benzene, are discussed in the light of the "molecular field effect" of Gans.