# One-Dimensional Nanostructure Engineering of Conducting Polymers for Thermoelectric Applications
## 3 Strategies to form 1D Conducting Polymer Nanocomposite Thermoelectric Materials
### Covalent Grafting of Conducting Polymers on 1D Nanofilers  
For preparation of polymer nanocomposite thermoelectric materials, the conventional physical mixing or in situ polymerization method still cannot effectively prevent agglomeration of the nanofillers, especially at high loading levels. Therefore, it poses as great challenge to achieve intimate interfacial connections between the conducting polymers and inorganic/carbon nanofillers to avoid aggregation and also assist carrier transport without scattering the carriers at the boundary. In 2017, [PERSON] et al. developed a P3 HT-based nanocomposite thermoelectric material through chemically grafting P3 HT onto the surface of double-walled CNTs (DWCNTs) [100]. As shown in Figure 12, amino-terminated P3 HT (P3 HT-NH\({}_{2}\)) was prepared via a Grignard metathesis polymerization process, which is a general methodology for preparing polythiophenes with small molecular weight distribution and large regularity. Then P3 HT-NH\({}_{2}\) was covalently grafted onto DWCNTs through an amidation reaction with the acyl moieties on the exterior of the acid-treated DWCNTs. The as-prepared P3 HT grafted DWCNTs (P3 HT-g-DWCNT) nanocomposites exhibit excellent dispersibility in organic solvents; hence, resulting in smaller aggregate sizes.  
Figure 11: (**a**) Schematic illustration showing the preparation procedure for the PPy/SWCNT nanocomposites via a template-directed in situ polymerization approach with water or aqueous ethanol as reaction medium. (**b**) SEM image of the composites with a SWCNT: Py ratio of 20 wt%, prepared in the medium of aqueous ethanol. Inset is a photo of the PPy/SWCNT nanocomposite thermoelectric film. (**c**) Bending measurement of the flexible film with a bending radius of 2 mm. (**d**) thermoelectric performance of the PPy/SWCNT nanocomposite film (40 wt%, aqueous ethanol) before and after bending up to 1000 times. (**e**) Dependence of mechanical stretching on the thermoelectric performance of the PPy/SWCNT nanocomposite film (40 wt%, aqueous ethanol). Insets are SEM images showing no cracks after bending or stretching. Readapted with permission from The Royal Society of Chemistry [96].  
The thermoelectric performance of the P3 HT-g-DWCNT films was investigated in comparison with the physically mixed P3 HT/DWCNT composite and pristine DWCNTs (Figure 12d-f). The chemically anchored P3 HT-g-DWCNT composite films exhibit a greatly improved Seebeck coefficient of 116. 6 uV K\({}^{-1}\), while the P3 HT/DWCNT composite by physical blending only yielded a Seebeck coefficient of 69.2 uV K\({}^{-1}\). It is believed that the intimate and large contact interface resulted from covalent bonding can facilitate the carrier transport by decreasing the carrier scattering at the boundary. Moreover, due to the reduced diameter of CNT bundles, the P3 HT-g-DWCNT composites also exhibit reduced thermal conductivity. The in-plane ZT value of the P3 HT-g-DWCNT films can reach up to 0.0069, which is about two-fold superior to the pristine DWCNT and the physically mixed P3 HT/DWCNT composites, demonstrating the effectiveness of this approach for fabrication of high performance thermoelectric nanocomposite materials.