The response time (to change from maximum to minimum contact angleCA for a drop of water) on the electrospun poly(N-isoporpylacrylamide) (PNIPA)/polystyrene (PS) fiber mats of 380, 990, and 1500nm diameter fibers was found to be 4-5s; whereas, on the 16 mu m diameter fiber it was more than five times slower. While the reported switching times were limited by the experimental design, they are in the micro- to millisecond for fiber diameters ranging between 100 and 500nm, in theory. The temperature-dependent-switch in CA values is attributed to the hydrogen bonding capability of PNIPA with water. The closer to superhydrophobic CA values at 65 degrees C was successfully described by the Cassie-Baxter (CB) state equation. The superhydrophilicity at RT was explained by hydrogen bonding as well as capillary forces provided by the fiber mat. The variations in the larger fibers' changes are attributed to lower surface area with reduced capillary driving forces for droplet spread.