pH-responsive ethylene vinyl alcohol copolymer membrane based on porphyrin supramolecular self-assembly

Abstract

A novel pH-responsive membrane based on porphyrin supramolecular self-assembly was investigated. 5,10,15,20-Tetrakis-(4-sulfonatophenyl)-porphyrin (TPPS) was loaded on a poly(2-(dimethylamino)ethyl-methylacrylate)-grafted ethylene-vinyl alcohol (PDMAEMA-grafted EVAL) membrane via electrostatic interaction. At pH above 3.0, TPPS assembled into H-aggregates on the membrane surface, which had little effect on the morphology of the membrane, and the membrane showed relatively higher water flux and lower PEG 20 000 rejection. When the pH was decreased to 1.0, TPPS transformed into J-aggregates which showed worm-like structures with large size, and then the membrane showed better surface wettability, decreased water flux and increased PEG 20 000 rejection. Higher loading amounts of TPPS and higher grafting content of PDMAEMA helped the membrane demonstrate a more notable pH-sensitivity. The novel supramolecular assembly-based membrane with good stability has potential for selectively permeating and rejecting some solutes during water treatment.