Switchable Wettability of Thermoresponsive Core–Shell Nanofibers for Water Capture and Release

Abstract

The capture and release of water from atmospheric humidity is a recognized green technology for efficient water harvesting. A key issue limiting this technology is the lack of water sorbents capable of consuming less heat energy when regenerate; therefore, the use of smart materials triggered by a small change in temperature resulting in altering their hydrophilic−hydrophobic properties is needed. In this research, we used a coaxial electrospinning technique to fabricate temperature-responsive hydrogel nanofibers with a core−shell structure for use in water capture and release in thermally simulated systems. The nanostructure, the water sorption capacity, and kinetics of the nanofibers were affected by varying the thickness of the shell layer, which consisted of a thermoresponsive polymer. The behavior of water capture and release at different humidity levels by the temperature-responsive core−shell nanofibers was demonstrated from 15 to 50 °C. At high humidity (∼95% RH), a dramatically higher water uptake (∼234% at 20 °C) was observed for the core−shell nanofibers than for the neat and composite nanofibers, resulting from the diffusion of water molecules which occurs in the shell layers that are present between the polymer chains. These results confirm that the application of temperature-responsive nanofibers could hold great promise for the development of responsive membranes for water-harvesting applications. KEYWORDS: electrospinning, thermoresponsive, poly(N-vinylcaprolactam), core−shell, water harvesting