Radiochemical grafting of methacrylic acid on polytetrafluoroethylene films

Methacrylic acid was grafted into the bulk of PTFE films 50 μm thick by irradiating the films in aqueous solutions of monomer containing CuCl2. The influences of radiation dose-rate and of temperature were investigated. The swelling of the grafted films was studied in the following solvents for the grafted branches: water, methanol, DMF and their mixtures. In each case the molar ratios corresponding to the limiting swelling were determined. It was further found that the grafted films swell in carboxylic acids such as methacrylic, acrylic and acetic acids. which are non-solvents for the grafted branches. This swelling is much slower than the swelling in good solvents. It is suggested that it results from a molecular association of the carboxyl groups of the solvent with those of the polymer. (author)