Selective Modification from PS-<i>b</i>-PMMA-<i>b</i>-P<i>t</i>BA Triblock Copolymer for Ultrafiltration Membranes

We demonstrate a feasible approach to fabricating nanoporous structures and their functionality using a triblock copolymer of polystyrene-b-poly(methyl methacrylate)-b-poly(tert-butyl acrylate) (PS-b-PMMA-b-PtBA). With casting the samples in the thin films, the continuous-type morphologies were formed as PS matrix consisting cylinders of PMMA and minor PtBA blocks. Perpendicular orientation of cylinder morphologies was exploited near two interfaces of air/polymer and polymer/neutral substrate, sandwiching the random orientation of cylinders in the interior of the film. Nondegradable, selective swelling–deswelling process of cylindrical (PMMA-b-PtBA) blocks generated nanopores with tunable pore sizes. Moreover, a simple hydrolysis of minor tBA blocks functionalized the nanopore surfaces and walls into poly(acrylic acid) layers. The pH-responsive water permeability of nanoporous membranes and their active switching with respect to biomolecules such as bovine serum albumin (BSA) were performed. These results suggest a platform to fabricate a stimuli-responsive ultrafiltration membrane using a tunable multiblock copolymer.