(34d) Dynamic Covalent Crosslinked Block Copolymers for Nanoporous Membranes

Membrane technology is expected to play a critical role in addressing the increasing global demand for clean water, with block copolymers (BCPs) emerging as promising materials for ultrafiltration (UF) membranes. Unlike conventional UF membranes which exhibit broad pore size distributions, self-assembling block copolymers can template pores with narrow size distributions, significantly enhancing performance in challenging separations. Co-continuous morphologies are particularly attractive for creating interconnected, nanoscale porous networks, and can be achieved via polymerization-induced microphase separation (PIMS). In PIMS, microphase separation is driven by the chain extension of an immiscible BCP, while covalent crosslinking traps the disordered, co-continuous morphology. However, conventional covalent crosslinkers used to arrest the disordered state limit post-polymerization processing of PIMS materials.

Here, we introduce dynamic covalent crosslinkers to overcome this limitation, demonstrating that dynamic disulfide bonds can arrest disordered morphologies while enabling melt processability. The block copolymer features a selectively etchable poly(lactide) (PLA) block and a styrenic matrix block, where styrene was copolymerized with crosslinker disulfide dimethacrylate (DSDMA). The resulting materials exhibited the disordered microphase separated morphology as confirmed by room temperature small-angle X-ray scattering (SAXS). Prior to selective removal of the PLA domains, the crosslinked materials are thermally moldable and self-healable. Upon PLA etching, porous materials are obtained, as confirmed by scanning electron microscopy (SEM). Overall, this work shows that incorporating dynamic covalent bonds into self-assembling block copolymers enable fabrication of reprocessable, nanostructured membranes.