Photopatterning of two stage reactive polymer networks with CO2-philic thiol–acrylate chemistry: enhanced mechanical toughness and CO2/N2 selectivity

Two stage reactive polymer (TSRP) networks can be programmed with spatially varying heterogeneity, presenting a new way of designing material structure and controlling or enhancing properties. The formulation framework is versatile and can be applied to many different monomers to achieve desired performance. Such versatility is demonstrated here by designing a novel TSRP formulation that includes poly(ethylene oxide) (PEO) and polydimethylsiloxane (PDMS) groups to enhance gas permeability compared to previous thiol–acrylate TSRP formulations where permeability of certain gasses was too low to accurately measure. With this higher permeability, the effects of patterned heterogeneity on CO2/N2 selectivity were studied. A TSRP with 24% to 34% by weight PEO and PDMS groups, patterned with 50μm circles of lower crosslinking density, is found to outperform the rule of mixtures prediction between permeability and selectivity for unpatterned materials. Comparing patterned films to stage 2 films shows an increase in permeability by up to 98% and an increase in selectivity by up to 67%. Patterned films also show improved mechanical toughness (up to 46% improvement) that previously studied TSRPs have. The material system presented in this study demonstrates a highly customizable approach for simultaneously improving permselective performance along with mechanical properties.