Reversibly thermochromic micro-fibres by coaxial electrospinning

A ‘solvent facilitated’ coaxial electrospinning process was used to produce reversible narrow temperature gap thermochromic, core-shell fibres. A thermochromic composite composed of crystal violet lactone (the leuco dye), bisphenol A (the developer) and 1-dodecanol (the phase-change solvent) was entrained as core material inside poly(methyl methacrylate) shells. A mutual core and shell solvent (chloroform) was used to obtain low interfacial tension between the core and shell spinning solutions. This enabled room temperature entrainment of the low molecular weight, low viscosity core fluid. In order to minimize the effect of light scattering and subsequently produce fibres with visible colour transitions, the fibres were produced with external diameters of 3–8 μm and core diameters of 1.7–5.7 μm. In order to produce core-shell fibres with repeated, reversibly thermochromic behaviour and a stable colour developed state, it was necessary to entrain a dye composite that contained an excess developer, essentially making this composite non-thermochromic prior to entrainment. The fibres were analyzed using SEM and DSC.