Effect of Cu@polythiophene yolk–shell nanofiller on the electrical, mechanical and thermal properties of poly(vinyl alcohol) thin films

Abstract

In this research, CuO2@ SiO2@polythiophene nanospheres are fabricated through a facile and stepwise synthesis process. Cu@polythiophene yolk–shell nanoparticles are obtained after converting Cu2O to Cu and removing the middle layer of SiO2 by using dilute acid. Transmission electron microscopy (TEM) confirms that the movable Cu cores are encapsulated in the interior of the hollow polythiophene nanospheres. The structure, morphology and optical properties of the synthesized nanoparticles are characterized by X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and ultraviolet–visible absorption spectroscopy. Uniform Cu@polythiophene nanoparticles with yolk–shell structure are applied as conductive filler in the poly(vinyl alcohol) matrix, and the effect of various nanofiller contents on the electrical, mechanical and thermal properties of the flexible polymer thin films is investigated. The FE-SEM images indicate that no agglomerates are seen on the surface of poly(vinyl alcohol) by adding the nanofiller amount up to 4 wt.%. Moreover, an increase in the direct current conductivity of nanocomposites is observed from 2 to 10 S/cm, as a result of the increase in contents of Cu@ polythiophene nanoparticles from 0.2 to 3.6 wt.%. Tensile test of thin films reveals that the mechanical properties of the nanocomposites are improved by increasing the content of nanofillers, so that when compared with the pure poly(vinyl alcohol) film, the poly(vinyl alcohol) with 4 wt.% of Cu@polythiophene shows a 238% and 23% increase in Young’s modulus and tensile strength, respectively. Besides, the results of the thermogravimetric analysis (TGA) indicate that the composite thin films are thermally more stable than the pure poly(vinyl alcohol) films.