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Fibrous thermoresponsive Janus membranes for directional vapor transport

Wearing comfort of apparel is highly dependent on moisture management and respective transport properties of the textiles. In today's used textiles, the water vapor transmission (WVT) depends primarily on the porosity and the wettability of the clothing layer next to the skin and is not adapting or responsive on environmental conditions. The WVT is inevitably the same from both sides of the membrane. In this study, we propose a novel approach by development of a thermoresponsive Janus membrane using electrospinning procedures. We, therefore, targeted a membrane as a bilayer composite structure by use of PVDF as one layer and a blend of PVDF and PNIPAM as the second layer changing wettability properties in the range of physiological temperatures. Tailored electrospinning conditions led to a self-standing membrane incorporating fiber diameters of 400nm, porosities of 50% for both layers within the Janus membrane. The WVT studies revealed that the combined effects of the Janus membrane's directional wettability and the temperature-responsive property results in temperature-dependent vapor transport. The results show that the membrane offers minimum resistance to WVT when the PVDF side faces the skin, which depicts the side with high humidity, over a range of temperatures. However, the same membrane shows a temperature-dependent WVT behavior when the blend side faces the skin. From room temperature of 25 C to an elevated temperature of 35 C, there is a significant increase in the membrane's resistance to WVT. This behavior is attributed to the combined effect of the Janus construct and the thermoresponsive property. This temperature-controlled differential vapor transport offers ways to adapt vapor transport independence of environmental conditions leading to an enhanced wearing comfort and performance to be applied in fields such as apparel or the packaging industry.