Electrically pressure sensitive poly(vinylidene fluoride)/polypyrrole electrospun mats

Non-woven mats with highly pressure-sensitive electrical conductivity has been prepared by electrospinning of poly(vinylidene fluoride) (PVDF) containing up to 23 wt% of polypyrrole (PPy) particles synthesized by using dodecylbenzene sulfonic acid (DBSA) as a dopant. The obtained mats have been characterized by dynamic mechanical thermal analysis, differential scanning calorimetry, thermogravimetric analysis, infrared spectroscopy, scanning electron microscopy and nitrogen adsorption BET. Electrical resistivity changes of PVDF/PPy blends were investigated during loading-unloading compressive cycles. It has been observed that the electrical resistivity varies reversibly with the applied compressive stress. The maximum sensitivity was obtained for a PVDF/PPy blend containing 13 wt% of PPy, manifesting an electrical resistivity drop of 10 orders of magnitude, i.e. from 10^17 to 10^7 Ω cm-1 upon application of a compressive stress of 5 MPa. This peculiar response can be attributed to the formation of stress-induced conducting pathways in the electrospun network. Considering the remarkable resistivity change and the reproducibility of the phenomenon after repeated loading-unloading cycles, this mat may found application as a pressure sensor.