Poly(N-isopropylacrylamide) grafting solution parameters for controlling temperature responsiveness in PET membranes fabricated using 248 nm KrF excimer laser

Abstract

A fast, simple, and efficient method to fabricate thermo-responsive membranes using 248 nm KrF excimer laser has been reported. For that process, monomer and crosslinker concentration effects on hydrogel network formation were studied during 248 nm pulsed laser polymerization (PLP) of poly(N-isopropylacrylamide) (PNIPAM) on laser ablated polyethylene terephthalate (PET) membranes. Water permeability of over 6 orders could be easily achieved, at room temperature, by appropriately tuning the hydrogel network parameters. The network growth could be controlled by reducing the monomer and crosslinker concentrations in the grafting solution. Caffeine diffusion studies established that controlled amounts of a model drug could be transported across the membranes. Crosslinker concentration had a more pronounced effect on the temperature responsivity of the grafted network across the lower critical solution temperature (LCST) of PNIPAM. A transition from positive to reverse temperature responsiveness was also observed for highly crosslinked grafted networks. Quantitative ATR-FTIR studies were performed to evaluate the relative amount of PNIPAM grafted in the membranes which was correlated to chain growth in pulsed laser polymerization.