(755f) Tunable Mesoporous Films from Graft Copolymers with Degradable Side Chains

Most membrane separations function through the use of a steric exclusion mechanism to effect the separation of target solutes from solution based on molecular size. Consequently, the development of polymer materials that enable the development of membranes with easily tunable pore sizes has been a major focus of recent membrane research. To this end, self-assembled block polymers have been used to prepare ultrafiltration membranes (pore diameters 10 nm - 100 nm) with tunable pore sizes, but the low molecular weight block polymers required to achieve smaller pore sizes and the poor mechanical properties of these low molecular weight materials limits their utility for many membrane separations from organic solvents. Here, to overcome this challenge a series of poly(styrene-graft-poly(lactide) methacrylate) copolymers have been prepared by a “grafting through” approach with styrene and poly(lactide) methacrylate macromonomers in a solution free radical polymerization reaction. Characterization of the copolymer materials by size-exclusion chromatography and H¹ NMR confirm good control over composition and molecular weights above 200 kDa. Films cast from these copolymers were characterized by scanning electron microscopy, small angle X-ray scattering, and dead-end filtration testing demonstrating that the pore size of the resultant membranes is easily varied from 15 nm to 5 nm by changing the molecular weight of the sacrificial, pore-templating poly(lactide) methacrylate group. Further exploration of structure-property relationships, membrane performance, and crosslinked materials shows potential utility of this materials platform for organic solvent separations.