Impact of Interfaces on the CO₂ Permeability of Photopatterned Two-Stage Thiolene Polymer Films

All-polymer composite films are useful in many applications. Two-stage reactive polymer networks fall into this category and are polymeric materials that can transition from one phase (stage 1─low cross-linking density, high gas permeability) to a second phase (stage 2─high cross-linking density, low gas permeability) upon application of UV light. As such, they can be spatially patterned to exhibit defined regions of stage 1 and stage 2. This paper explores the effect of pattern geometry at small length scales (10 μm feature sizes) on the CO₂ permeability of spatially patterned stage 1 and stage 2 films. The small patterns reduce gas permeability beyond a rule of mixtures estimate due to the volumetric quantity of interfacial material between the two phases, irrespective of the specific pattern geometry.