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A~stract: Interpenetrating networks of polydimethylsiloxane and polymethacrylic acid have.been .prepare~. The structure of these materials swollen in heavy water has been investigated USIng small angle neutron scattering. A correlation function has been used to describe this structure, and it is found that the characteristic correlat~~n length of the swollen polymethacrylic acid phase increases linearly with o~posltJon. The prese~ce of a diffuse interface between the two phases is indicated from an analysis of the scattered intensity at high scattering vectors.

Interpenetrating networks have been prepared using poly(dimethylsiloxane) as the host network and polymethacrylic acid as the guest network, i.e. polymerised and crosslinked in the presence of the siloxane network. These networks were swollen to equilibrium in dilute aqueous potassium chloride solutions and used as membranes to separate a solution of potassium chloride from pure water. The concentration of potassium chloride either side of each membrane was monitored as a function of time by conductivity measurements. From these data, the diffusion coefficient of potassium chloride in the membranes was calculated as a function of polymethacrylic acid content for temperatures of 303, 318 and 333K. Values of the diffusion coefficient were between 3 x 10−7cm2s−1 and 19 x 10−5 cm2 s−1. The activation energy of the diffusive process decreased linearly with the increase in water content of the networks.