Controlled synthesis of alkylthio-substituted poly(thienylene vinylene) and its carbon nanotube composites for enhanced thermoelectric performance

Abstract

Semiconducting polymers are lightweight, low cost, and easy to manufacture, making them promising candidates for application in electronic devices. In this study, poly(thienylene vinylene) (PTV) with alkylthio side chains, poly[3,4-bis(2-ethylhexylthio)thienylene vinylene] (P3,4EHTTV), was successfully synthesized using an environmentally friendly polymerization system that employs neither transition-metal catalysts nor halogens. The polymerization proceeded via a chain-growth mechanism, exhibiting a “quasi-living” nature. P3,4EHTTV was then combined with single-walled carbon nanotubes (SWCNTs) to fabricate nanocomposite thin films with thermoelectric (TE) properties. The strong S–π and π–π interactions between P3,4EHTTV and SWCNTs promoted the close wrapping of P3,4EHTTV around the SWCNTs, leading to effective dispersion of SWCNT bundles. The electrical conductivity of P3,4EHTTV/SWCNT nanocomposites demonstrated a pronounced p-doping effect and increased carrier mobility. Additionally, the P3,4EHTTV/SWCNT system showed favorable charge distribution and improved alignment of energy levels, contributing to considerably improved TE properties, with a record-breaking power factor of 363.7 μW m⁻¹ K⁻². These findings highlight the importance of structural design in PTV and alkylthio side-chain engineering for optimizing TE performance.