Isoporous membrane with glucose mediated toughness and protein sieving prepared from novel block copolymers containing boronic acid moieties

Abstract

Bio-responsiveness is widely found in organisms. Incorporation of this function to membranes is an effective way to endow membranes with new functionalities. In this work, phenylboronic acid groups were used as the glucose binding moieties to construct a novel block copolymer polystyrene-block-poly(4-vinylphenylboronic acid) (PS-b-P4VBA), which was observed to assemble easily into periodic nanostructures in annealed thin films due to strong immiscibility between PS and P4VBA segments. Isoporous membranes were then fabricated from this newly synthesized copolymer following the procedure of self-assembly combined with non-solvent induced phase separation (SNIPS). The prepared isoporous membrane was determined to show a notable glucose dependent permeability that was ascribed to the switch of P4VBA conformation when it was bonded with glucose molecules. This interpretation was demonstrated by the glucose tailored surface wettability and protein sieving. Moreover, the glucose was found to serve as a molecular binder for the P4VBA, and toughness of dried isoporous membranes increased by ∼4 times. The reason was ascribed to the formation of new linkage between glucose and P4VBA that was verified by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis. Our results prove that the binding between glucose and boronic acid can be used to regulate both the separation performance and mechanical strength for isoporous block copolymer membranes. As far as we know, this performance has been rarely achieved for such membranes before.