Coil dimensions of poly(methyl acrylate) in the cosolvent medium of carbon tetrachloride and methanol

Abstract

The intrinsic viscosities [η] of some poly(methyl acrylate) fractions at 35°C have been measured in a mixture of carbon tetrachloride and methanol (CCl₄ + CH₃OH) at different liquid compositions. The [η]-composition plot shows a maximum for each fraction at composition Ø_CH3OH (volume fraction of methanol) = 0.33. Values of the Huggins constant, determined from the slope of a plot of ηSP/C, versus C exhibit a minimum at the same composition in the Huggins constant-composition plot for almost all fractions. Huggins constant values indicate association of poly(methyl acrylate) chains in the poorer cosolvent mixtures and the association increases as the solvent becomes poorer. The molecular association decreases with increase in molecular weight. The unperturbed dimension (Kθ), determined from a Burchard, Stockmeyer, Fixman plot and also from other methods, varies with solvent composition and exhibits a maximum at Ø_CH3OH = 0.33. The molecular extension parameter αη decreases with decrease in molecular weight. Its variation with cosolvent composition is rather different: η_η shows a minimum at η_CH3OH = 0.33. A possible reason for this is discussed.