A monomer immersion sequential method for preparing PDMS-PMAA interpenetrating polymer networks (IPNs) was developed. Immersion of pre-IPN films in the 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 permeable to water-soluble compounds. Laser scanning confocal microscopy (LSCM) 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 morphology spectrum was attributed to a monomer concentration gradient created by monomer evaporation during handling of the pre-IPN Blm, as well as to substrate-dependent surface thermodynamic effects. The layer near the surface with dispersed hydrogel domains rendered such IPN membranes impermeable to water-soluble compounds.