Temperature- and pH-sensitive nylon membranes prepared via consecutive surface-initiated atom transfer radical graft polymerizations

Thermo- and pH-responsive nylon membranes were prepared via consecutive surface-initiated atom transfer radical polymerizations (ATRPs) of N-isopropylacrylamide (NIPAAm) and N,N′-dimethyl aminoethyl methacrylate (DMAEMA). The amide groups of the membrane and pore surfaces were first activated for the immobilizing of alkyl halide ATRP initiator. The kinetics study revealed that the chain growth from the membranes was consistent with a “controlled” process. The dormant chain ends of the grafted NIPAAm polymer (PNIPAAm) or DMAEMA polymer (PDMAEMA) on the nylon membranes could be reactivated for the consecutive surface-initiated ATRP to produce the corresponding nylon membranes functionalized with PNIPAAm-b-PDMAEMA or PDMAEMA-b-PNIPAAm diblock copolymer brushes. The permeation of aqueous solution through the functional membranes showed an abrupt change with temperature between 30 and 35 °C, and pH between 6 and 8. The temperature- and pH-responsive permeation through the functional nylon membranes was found to be reversible and irrespective of the sequence of the graft segments.