Reversible thermochromic switching of fluorescent poly(vinylidene fluoride) composite containing bis(benzoxazolyl)stilbene dye

A series of fluorescent composites was prepared via melt compounding poly(vinylidene fluoride) with 4,4′-bis(2-benzoxazolyl)stilbene. The composite containing moderate amount of the stilbene (e.g. 0.5 wt%) exhibited a reversible thermochromic transition between blue and green fluorescence. The composite emitted green light upon UV excitation at room temperature, while it changed to blue at the temperature above the melting point of the poly(vinylidene fluoride). Upon cooling to room temperature, an intense green emission was regenerated. Such a conversion between green and blue shades was reproducible via repeated heating and cooling cycles. This thermochromic switching was found to originate from the dispersion of dye molecules in the composite.