The influence of molecular architecture on the surface activity of vinyl alcohol-acetate copolymers

The interfacial behavior of a family of blocky and random vinyl alcohol-acetate copolymers and their parent polyvinyl alcohol was studied. The vinyl acetate content and the intramolecular distribution were the only variables in the molecular architecture. Polymer adsorption and the effect of spread layers of these (co)polymers at the water- 1-butanol interface were studied with the static drop shape and the dynamic drop volume methods, and in addition with a novel method that records the retardation of mass transfer across an interface as caused by polymer adsorption. The three measuring techniques provide consistent views as to which molecular parameters determine the efficiency and mode of copolymer adsorption. Not the copolymer-solvent interaction parameter is relevant in this system, but rather the molecular architecture of the copolymers as expressed by the product of the mass average vinyl acetate sequence length and the vinyl acetate mole fraction. In addition, mass transfer studies provide information on the compressibility of the copolymer layers, the effectiveness of adsorption, and the onset of adsorption fractionation.