ABAC Tetrablock Terpolymers for Tough Nanoporous Filtration Membranes

Abstract

Nanoporous poly(styrene)-b-poly(isoprene)-b-poly(styrene) (PS–PI–PS) was prepared from PS–PI–PS–PLA (PLA = poly(d,l-lactide)) tetrablock terpolymer precursors. Hydroxy end-functionalized PS–PI–PS was synthesized by sequential anionic polymerizations and used to initiate the ring-opening polymerization of d,l-lactide. A combination of small-angle X-ray scattering, transmission electron microscopy and scanning electron microscopy data supports a core–shell cylinder morphology with PLA as the core component. The inherently robust mechanical properties associated with PS–PI–PS block copolymers provide the materials with enhanced flexibility and toughness compared to analogous nanoporous polystyrene samples prepared by etching of PS–PLA diblocks. Composite membranes containing nanoporous PS–PI–PS on top of microporous poly(ether sulfone) (PES) were prepared by direct spin-coating and also by a salt-plate coating/film-transfer strategy. Nanopores (dpore ≈ 15 nm) were created by a combination of reactive ion etc...