Recently, organic thermoelectric (TE) materials have sparked intense interest due to their attractive advantages over inorganic materials. Among various conducting polymers, polypyrrole (PPy) is widely applied in the fields of microelectronics, electrochemistry and biological technology because of its good environmental stability, low toxicity and adjustable electrical conductivity. However, the relatively low TE property plus difficult dissolution and dispersion characteristics of PPy endow PPy and its composites with TE performance far below the level for industrial application. Therefore, it is necessary to conduct thorough research on PPy composite films for excellent TE performance in order to solve this issue facing the preparation of such films.
Taking advantage of high electrical conductivity of single-walled carbon nanotube (SWCNT) and facile chemical oxidative polymerization method, the study of PPy/SWCNT composite TE films has been developed recently by Lirong Liang, an MS student co-supervised by associate professor Cun-Yue Guo at the University of Chinese Academy of Sciences (UCAS) and associate professor Guangming Chen at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS). Their findings are of great significance for developing novel polymer TE materials and their applications.
Large-area, super flexible (minimum bending radius < 0.6 mm), stretchable and mechanically stable TE films of PPy/SWCNT cable-like nanostructure composites were prepared using in situ polymerization and vacuum filtration method, with the aid of reaction medium-ethanol to regulate the enwrapped structure of PPy on the surface of SWCNT (Fig. a). More importantly, after mechanical bending or stretching, no obvious deterioration of TE performance was found. This work has been published in Journal of Materials Chemistry C (http://pubs.rsc.org/en/Content/ArticleLanding/2016/TC/C5TC03768A). On this basis, PPy nanowire was firstly synthesized by chemical polymerization method considering their outstanding features of one-dimensional (1D) nanostructure of conducting polymers, and then a unique layered morphology of PPy nanowire/SWCNT composite film was fabricated via convenient physical mixing followed by vacuum filtration (Fig. b). The as-fabricated composites afforded greatly enhanced TE performance with the maximum power factor of 21.7 ± 0.8 μW m-1 K-2. This work has been published in Composites Science and Technology (http://www.sciencedirect.com/science/article/pii/S0266353816301622).
The work is supported by NSFC (51343005 and 51573190) and the 135 Incubating Project of ICCAS (PY-2015-35).