Preparation and characterization of a novel piezoelectric nanogenerator based on soluble and meltable copolyimide for harvesting mechanical energy

The quasistatic piezoelectric coefficient (d(33)) of the state-of-the-art bulk polymers is lower than 38 pC N-1, extremely restricting their application in the fields of next generation of smart and wearable devices. Herein, a novel soluble and meltable piezoelectric bulk copolyimide with the d(33) of about 420 pC N-1 has been successfully synthesized by co-polymerizing pymmellitic dianhydride with p-phenylenediamine and the specially designed NH2-ended imidazole ionic liquid. Molecular structure, solubility, melt processability, and piezoelectricity of the resulting piezoelectric copolyimide have been extensively investigated. Relevant results reveal that the d 33 value of the obtained piezoelectric copolyimide is found to be 10 and 50-100 times higher than the reported bulk poly (vinylidene fluoride) and polyimides, respectively. It still surpasses 250 pC N-1 as the storage temperature approaches 150 degrees C, evidently higher than that of the previously reported polymer based piezoelectric materials. The developed copolyimide shows outstanding piezoelectricity reliability, benefiting from the semicrystallinity of the resulting copolyimide at room temperature. A maximum output voltage of about 219 mV can be instantaneously obtained once a tiny periodical force is loaded on the copolyimide based piezoelectric nanogenerator (PENG). Meanwhile, an output power of about 1.17 mW can be reached for the developed PENG, implying large potential application in the sectors of smart tactile devices, electronic skins, and self-powered biomedical nanorobots etc.