Interconnected Nanoporous Polysulfones by Microphase Separation of Randomly End-linked Copolymer Networks

Co-continuous polymer nanostructures formed by both equilibrium and kinetic routes have been widely studied due to the attractive combination of material properties they offer in many contexts. Our group has recently shown randomly end-linked crosslinked networks (RECNs) can yield co-continuous nanostructures over wide composition windows of 30 - 45 wt. % depending on the strand parameters. Previously, the use of RECNs based on polystyrene (PS) has been focused, which can be converted to interconnected nanoporous PS by selectively etching the second microphase, polylactic acid (PLA). However, the brittle nature of the PS phase makes it challenging to apply these materials as membranes. To overcome this, we employ telechelic polysulfone (PSU) to generate co-continuous PSU/PLA RECNs and interconnected nanoporous PSU. Uniaxial tensile testing on PSU/PLA and PS/PLA at 80 °C was performed, above the glass transition temperature of PLA, to isolate the effect on mechanical properties of shifting from PS to PSU. Co-continuous PSU/PLA displays five times greater stretchability and three times higher Young’s modulus than co-continuous PS/PLA, which gives rise to a dramatic improvement in the properties of the resulting nanoporous membranes.