Temperature-Responsive Structurally Colored Fibers via Blend Electrospinning

Achieving fibers that change color with temperature may be promising for applications such as sensors and smart wearable textiles (woven and nonwoven). In this study, temperature-responsive cholesteryl ester liquid crystal formulations were blended with polycaprolactone or polystyrene using chloroform as a solvent for electrospinning to achieve thermochromic nonwoven products. Using polystyrene, beaded fibers were achieved and the thermochromic behavior was only observed under polarized light microscopy. To achieve fibers with visible thermochromic behavior observed by a video camera or smart phone, polycaprolactone was used as a carrier polymer. The comparison between polystyrene and polycaprolactone provides insight into polymer/solvent selection achieving responsive materials via blend processing. High loadings of liquid crystal were achieved with polycaprolactone, blends of 10 wt % polycaprolactone with 15 wt % liquid crystal formed fibers (fiber contained 60 wt % liquid crystal). Colored fibers could be achieved by varying the formulation of the liquid crystal. For example, liquid crystal formulations that were green at ambient conditions resulted in fibers that were green at ambient conditions (22 °C). Nonwoven fibers with dynamic color with temperature were also demonstrated. For example, liquid crystal formulations were colorless at ambient conditions and underwent a reversible color change from red to blue when heated and cooled between 32 and 37 °C. When incorporated into fibers, the fiber mats changed from white at ambient conditions to red at 32 °C to blue at 37 °C. The color change was reversible over multiple cycles.