Bicontinuous Porous Nanomaterials from Block Polymers Radically Cured in the Disordered State for Size-Selective Membrane Applications

Solution-cast blends of lamellar-forming poly(styrene-stat-butadiene)-block-poly(lactide), P(S-s-B)-b-PLA, and peroxide were heated above their effective order-disorder transition temperature, T_ODT, to chemically arrest the locally segregated and bicontinuous domains of the block polymer in the fluctuating disordered state. Selective hydrolysis of the PLA domains produced porous networks characterized by using a combination of small-angle X-ray scattering, scanning electron microscopy, and nitrogen sorption analysis. The location of T_ODT varied with parameters of the curing system, including peroxide identity and loading, leading to observable changes in the product morphology and pore characteristics with curing temperature. Disordered, bicontinuous structures exhibiting narrow pore size distributions were generated in several cases, rendering the materials attractive for size-selective membrane applications. The versatility of the radical curing approach is highlighted via extension of the solution-based casting protocol toward the preparation of selective membranes for ultrafiltration.