Crystal polymorphism in polydiacetylene-embedded electrospun polyvinylidene fluoride nanofibers.

In this study, polydiacetylene (PDA) is embedded in electrospun polyvinylidene fluoride (PVDF) nanofibers for the preparation of mats with dual colorimetric and piezoelectric responses. The diacetylene monomers are self-assembled during the electrospinning process. The PDA-embedded PVDF nanofibers in the blue phase are obtained via photo-polymerization upon UV-light irradiation. The colorimetric transition of the nanofibers is studied as a function of temperature using a spectrophotometer. The morphology and crystal polymorphism of the nanofibers are investigated. The results show that the addition of PDA increases the diameter of the nanofibers due to the increase in the electrospinning solution viscosity. The results of Fourier transform infrared and wide angle X-ray diffraction demonstrate that PDA has the effect of inhibiting the growth of non-polar α-phase crystals, while promoting the growth of the polar β-phase. However, the red phase of PDA-embedded PVDF exhibits a lower intensity of the β-phase in comparison to that of the blue phase. In fact, the blue-to-red color transition of the PDA-embedded electrospun PVDF nanofibers is accompanied by the variation of piezoelectric signaling caused by variations in the β-phase. This phenomenon creates great potential in commercial detection sensors in addition to their colorimetric detection properties.