Free volume correlation with electrical conductivity of polycarbonate/reduced graphene oxide nanocomposites studied by positron annihilation lifetime spectroscopy

Abstract

The reduced graphene oxide (RGO) was added to polycarbonate (PC) through solvent mixing. The influences of RGO on the free volumes and electrical conductivity of PC were systemically studied by positron annihilation lifetime spectroscopy (PALS), Fouriertransform infrared spectroscopy, transmission electron microscope, and electrical conductivity measurements for PC/RGO nanocomposites. The nanosized effect, good conductivity of RGO, and strong interfacial interaction between RGO and PC result in the low conductive threshold of 0.36 wt %. Ten orders of magnitude increase in electrical conductivity was obtained. The results of PALS indicate the properties of free volumes fluctuate around the conductive percolation threshold. The conformational change of PC segments in the interfacial region induced by the strong interfacial interaction leads to an increase in free volume radius. The concentration of free volume decreases due to the depression of free volume holes as the introduction of RGO. Significantly, an exponential function is proposed to describe the effect of relative fractional free volume on the electrical conductivity, suggesting that free volume plays an important role in regulating electrical conductivity of PC/RGO. The physical quantity f d that refers required fractional free volume of polymer composites from insulating to conducting phase is found.

Correlation between microstructure and properties of graphene oxide/waterborne polyurethane composites investigated by positron annihilation spectroscopy

“…The f r increased at high GO loading is due to the little restriction of chain movement, causing by the agglomeration and weak interfacial interaction. 28,36 This results quantitative conrmed the results of SEM (Fig. 1c-g), where dense fracture surface was observed for the composite with low load level and loose fracture surface was observed for the composite with high load level.…”

“…3b, I 3 decrease with increasing GO content, indicating a decrease in concentration of free volume in the composites, which is similar to the results of PC/RGO composites reported by Zhong and co-workers. 28 This may be interpreted as the reason that the introduction of GO nanosheets with large surface in WPU matrix results in a highdensity interfacial region and decrease the concentration of free volume holes. 28 The relative free volume fraction (f r ) is plotted in Fig.…”

“…28 This may be interpreted as the reason that the introduction of GO nanosheets with large surface in WPU matrix results in a highdensity interfacial region and decrease the concentration of free volume holes. 28 The relative free volume fraction (f r ) is plotted in Fig. 3c showing that the composites have lower f r as compared to pure WPU.…”

“…The smallest free volume was observed at 0.5 wt% rGO sample, which can be ascribed to the interfacial interaction between rGO and PVA. The inuence of rGO on the free volume and conductivity of polycarbonate composites were systemically studied by PALS in Zhong group, 28 the results of PALS indicate the properties of free volumes uctuate around the conductive percolation threshold.…”

“…Actually, interfacial interaction exists in polymer composites in most cases, thus positive or negative deviations occurred between the experimental results and the calculated results. 25,26 The interaction parameter b (an intuitionistic characterization of the interaction) was then introduced to characterize the interfacial interaction between polymer matrix and nanoller, 27,28 which provide new methods for the correlation between microstructure and properties, while the utilization of PALS in GO/WPU system has rarely been reported.…”