Viscometric study of poly(methyl methacrylate-g-propylene oxide) and respective homopolymers

A viscometric study was performed on samples of poly(methyl methacrylate-g-propylene oxide) and on the respective homopolymers (PMMA and PPO). The copolymers were composed of poly(methyl methacrylate) backbone and uniform poly(propylene oxide) branches (PPO), in different proportions, synthesized by a macromonomer technique. In the viscometric measurements, three different solvents were employed at 25 °C: chloroform, toluene and carbon tetrachloride, the last one being selective for the grafted-chains. Six different equations were used to calculate intrinsic viscosities and viscometric constant values: Huggins, Kraemer, Martin and Schulz-Blaschke by graphic extrapolation, and Solomon-Ciuta, Deb-Chanterjee and again Schulz-Blaschke by a single point determination. The latter determination presents the obvious advantage of being faster, which is desirable, particularly in industrial laboratories. The results were compared and it was verified that, in chloroform and toluene, the single point determination was suitable for homo- and copolymers analyzed, particularly when the Solomon-Ciuta equation was employed. However, the determinations performed in the selective solvent for the grafts, in which the copolymers assumed a contracted configuration, led to lower values of intrinsic viscosity, similar in all samples, and a higher percentage difference between graphic extrapolation and single point determination data.