Ultrasonic Absorption of Polymer Solutions

Abstract

IT is well known that the presence of a small amount of low-absorption solute in a highly absorbing solvent will reduce the absorption of the solution by much more than would be expected from simple proportionality. This is the case for mixtures of benzene (high absorption) with methyl methacrylate (low absorption). Wada and Shimbo¹ have shown that if polymethylmethacrylate is added to a benzene–methylmethacrylate mixture the resultant absorption is higher than in the absence of the polymer, although remaining less than that for the pure benzene. They suggested that this rise in absorption is caused by some of the monomer becoming ‘enclosed’ within the polymer chains so that it is no longer effective in reducing the solution's absorption. It is possible, however, to account for this rise in absorption without assuming ‘enclosure’.