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 (CCl 4 + CH 3OH) at different liquid compositions. The [η]-composition plot shows a maximum for each fraction at composition ø CH 3OH (volume fraction of methanol) = 0.33. Values of the Huggins constant, determined from the slope of a plot of η SP 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 ( K θ ), determined from a Burchard, Stockmeyer, Fixman plot and also from other methods, varies with solvent composition and exhibits a maximum at ø CH 3OH = 0.33. The molecular extension parameter α η decreases with decrease in molecular weight. Its variation with cosolvent composition is rather different: η η shows a minimum at η CH 3OH = 0.33. A possible reason for this is discussed.