Thermo- and pH-responsive polypropylene microporous membrane prepared by the photoinduced RAFT-mediated graft copolymerization

Thermo- and pH-responsive polypropylene microporous membrane prepared by photoinduced reversi addition-fragmentation chain transfer (RAFT) graft copolymerization of acrylic acid and N-isopropyl lamide by using dibenzyltrithiocarbonate as a RAFT agent. Attenuated total reflection-Fourier transfort infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scann electron microscopy (FE-SEM) were used to characterize the structural and morphological changes o the membrane surface. Results of ATR/FT-IR and XPS clearly indicated that poly(acrylic acid) (PAAc) ar poly(N-isopropyl acrylamide) (PNIPAAm) were successfully grafted onto the membrane surface. The graf ing chain length of PAAc on the membrane surface increased with the increase of UV irradiation time, ar decreased with the increase of the concentration of chain transfer agent. The PAAc grafted membrane-containing macro-chain transfer agents, or the living membrane surfaces were further functionaliz via surface-initiated block copolymerization with N-isopropyl acrylamide in the presence of free rad cal initiator, 2,2'-azobisisobutyronitrile. It was found that PNIPAAm can be grafted onto the PAAc graft membrane surface. The results demonstrated that polymerization of AAc and NIPAAm by the RAFT meth could be accomplished under UV irradiation and the process possessing the living character. The PPM with PAAc and PNIPAAm grafting chains exhibited both pH- and temperature-dependent permeability aqueous media. (C) 2009 Elsevier B.V. All rights reserved