Polystyrene (PS) nanofiber mats grafted with poly(N-isopropylacrylamide) (PNIPAM) demonstrated switchable wetting properties by utilizing the lower critical solution temperature (LCST) properties of PNIPAM. The technology is inspired by the water collection mechanism of Namib Desert beetles (Stenocara gracilipes) in their native South African desert that only receives 1.4 cm of rain annually. The back surfaces of these beetles are composed of hydrophilic regions, which capture moisture from air, and hydrophobic zones that collect excess water for the beetle's consumption. Due to the random deposition of nanofibers produced by electrospinning, innately hydrophobic PS can produce fibers with water contact angle (WCA) of 158.30. In order to graft PNIPAM on the surface of the fibers, the mats are exposed to a photo-attachable (to any -CH bond) initiator for atom transfer radical polymerization (ATRP) of NIPAM. At 400C, the WCA was able to reach 110-1200 while at temperatures less than 320, the fiber mats become superhydrophilic (WCA = 00). The synergistic effect of the nanoscale roughness of the fiber mats, which can easily be produced in a large scale via electrospinning, and the temperature-triggered wettability of the grafted polymer can significantly help address water supply problems in dry areas.

Temperature-switchable wettability of PS-g-PNIPAM fiber mats

246th National Meeting (2013)

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