Preparation of PDMS-PMAA interpenetrating polymer network membranes using the monomer immersion method

A monomer immersion sequential method for preparing PDMS-PMAA interpenetrat ing polymer networks (IPNs) was developed. Immersion of pre-IPN films in th e guest: monomer throughout synthesis ensured an even monomer concentration profile and produced a uniform bicontinuous morphology throughout the IPN indicative of phase separation by spinodal decomposition. Such IPNs were pe rmeable to water-soluble compounds. Laser scanning confocal microscopy (LSC M) of the swollen IPNs allowed direct visualization of the morphology. PDMS -PMAA sequential IPNs synthesized while in contact with surfaces were also examined. Contact with glass or air during synthesis resulted in spatially varying morphology ranging from dispersed hydrogel domains near the surface to a bicontinuous morphology some distance below the surface. The morpholo gy spectrum was attributed to a monomer concentration gradient created by m onomer evaporation during handling of the pre-IPN Blm, as well as to substr ate-dependent surface thermodynamic effects. The layer near the surface wit h dispersed hydrogel domains rendered such IPN membranes impermeable to wat er-soluble compounds.