Smart electrospun mats of poly(vinylidene fluoride) with thermochromic pigment

Smart materials are characterized by responding, in a controlled manner, to external stimuli through changes in their properties. Specifically, thermochromic materials have been gaining importance because of the functionality of color change when detecting a temperature variation. In this context, thermochromic electrospun mats can display improved sensitivity and interaction with the external environment due to their fibrous structure, elevated porosity, and high surface area. In this study, poly(vinylidene fluoride), (PVDF) mats containing different weight fractions of thermochromic pigment were developed through the electrospinning technique to be used as intelligent temperature sensors. The thermochromic pigment was characterized to evaluate particle size and shape, composition, and thermochromic activation temperature. The used pigment is composed of melamine–formaldehyde core–shell microcapsules with diameters ranging from 0.6 to 5.5 μm and crystal violet lactone (CVL) as the leuco dye of the thermochromic system, exhibiting a color change from black to white at 40 °C. For the electrospun mats, the morphology, thermal properties, and thermochromic behavior were evaluated. The use of the electrospinning technique allowed the encapsulation of pigment microcapsules in the PVDF fibers. The electrospun mats exhibited an instantaneous reversible thermochromism, even after several heating–cooling cycles, showing a transition temperature of around 36—37 °C, indicating that they have excellent properties to act as temperature sensors.