Interfacial behavior of acetalized poly(vinyl alcohol) monolayers observed by Brewster angle microscopy and canal surface viscometry

The interfacial properties of polymer monolayers at the air/water interface has been determined by the observation of morphological changes and the measurement of surface shear viscosity. Brewster angle microscopy (BAM) was applied to the monolayers of the acetalized poly(vinyl alcohol)s having alkyl side chains of various lengths. The monolayers of these polymers form coherent domains even at a large surface area, and the longer the side chains are, the smaller the degree of domain deformation is. Canal surface viscometry also showed that sheer viscosity of the monolayer increases with the increase in the number of side-chain carbons. These findings indicate that the cohesive force is stronger among the side chains protruding out of the interface when the alkyl chains are longer, so that the entire monolayer becomes more viscous while retaining the liquid-like character.