| In this paper, atom transfer radical polymerization was conducted on the surface of PET track-etched membranes. By using different grafted functional monomers, three kinds of novel environment-sensitive membranes have been prepared.To immobilize the ATRP initiator onto PET track-etched membrane surface, PET track-etched membrane should be pretreated by reacting with ethylenediamine to introduce active group, then the aminofunctionnalized membrane reacted with 2-bromoisobutyryl bromide (2-BIB), followed by grafting with the stimuli-responsive polymers poly(2-hydroxyethyl methacrylate)(PHEMA) or poly(N-isopropylacrylamide)(PNIPAAm), which have pH or thermal modulated permeability properties, using ATRP method. The grafted membranes were analyzed by XPS, ATR-FTIR, TGA, grafting rate measurements and water contact angle measurements. The results showed that PHEMA or PNIPAAm had been grafted on the surfaces of PET track-etched membrane successfully. Then the pH or temperature modulated permeability properties of the membranes were characterized by water flux measurement. The PHEMA grafted membrane acts as a pH switch, and the water flux has a leap from neutral to acidic environment (pH range 4-5). For the PNIPAAm grafted membrane, the water flux has a leap near the temperature range of 30℃to 35℃. The results showed that the pH or thermal modulated permeability properties can be introduced onto PET track-etched membrane surface by "living"/controlled radical polymerization method ATRP.A new concept of bi-signal or multi-signal sensitive membrane was presented. First, PHEMA was grafted on the surface of PET track-etched membranes, and because the end of the grafting PHEMA chain can still initiate the polymerization of other monomers by ATRP method, then PNIPAAm was grafted on the end of PHEMA chain by re-grafting. As a result, membranes with two grafting layers were prepared. By controlling the reaction conditions, the grafted membranes can response to both temperature and pH value. |
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