Polymerization of 16-heptadecenoic acid monolayers

Monolayers of heptadecenoic acid (vinyl acid) were spread at a gas-water interface. The terminal double bond of the vinyl acid enabled it to be polymerized on exposure to UV radiation. Pressure-area isotherms for both monomer and polymer vinyl acid were then recorded and compared with isotherms from similar compounds.Preliminary studies were conducted to minimize the degree of dissolution of the fatty acid. The polymerization kinetics were examined by the use of UV spectroscopy and measurements of the reduction in the area occupied by the film at a constant surface pressure. The reaction appeared to follow zero-order kinetics after an initial acceleration period. The rate constant for the reaction increased with increasing surface pressure.A dynamic mechanical test was performed to determine the mechanical properties of monolayers at the gas-water interface. Films were polymerized to various conversions and then examined to determine the relation between mechanical properties and conversion. A simple model is proposed to correlate the monolayer's structure and the dynamic mechanical data.