Membrane-based technologies are increasingly recognized as important tools for addressing water scarcity challenges as global water demand increases. Self-assembled block polymers have emerged as promising membrane materials, where periodic domains can be transformed into well-defined pores through etching, swelling, or controlled solvent removal. As continuous pores spanning the material cross section are crucial for membrane applications, microstructures such as hexagonally-packed cylinders and double gyroids are commonly targeted. The Hillmyer group has previously demonstrated various versatile approaches for preparing nanoporous materials using disordered block polymers, including heating a lamellar diblock polymer up to the order-disorder transition temperature (T_ODT) and trapping it in this state. Above the T_ODT, the block polymer loses long range spatial correlations but remains locally microphase separated, allowing a bicontinuous morphology to be achieved.
In this work, the functionality of co-continuous disordered polymers is expanded with an ABC triblock platform. The polymers are comprised of a styrene-based rigid matrix block (A) and a poly(lactic acid) (PLA) etchable pore-forming block (C), while a short pore-lining midblock (B) is introduced as a handle to tune pore surface properties. As hydrophilic membrane surfaces are commonly desirable for fouling resistance, hydrophilic poly(oligo ethylene glycol methacrylate) (POEGMA) was selected as the midblock. Due to its miscibility with PLA, the midblock co-localizes with PLA and remains on the pore surface upon hydrolysis of the PLA block. The triblock polymer phase space is investigated using rheology and small-angle X-ray scattering (SAXS). As POEGMA is miscible with PLA and a relatively short midblock was used, the presence of an order-disorder transition was demonstrated to be largely predicted by the segregation strength χ_ACN. The nanoporous hydrophilic materials were further characterized by scanning electron microscopy (SEM), nitrogen sorption, and contact angle measurements.

Wui Yarn Daphne Daphne Chan

Appearances