Robust organic semiconductor thermoset composite films based on Crystallization-Driven Self-Assembled nanofibers of Poly (3-hexylthiophene) block copolymers

Crystallization-driven self-assembly (CDSA) has been widely used as a fascinating technique to prepare nano structures, especially nanofibers containing conjugated polymers, while realizing its practical application remains challenging. For the wide application of semiconductor micelles, amphiphilic poly(3-hexylthiophene)-b-poly(epsilon-caprolactone) (P3HT-b-PCL) block copolymers were synthesized to obtain stable nanofiber dispersions via CDSA, and subsequently combined with epoxy resin systems to prepare composite films. The thermoset composite films containing 12.5 wt% nanofibrous P3HT exhibited satisfactory mechanical strength and flexibility. They were further doped in an acetonitrile solution of Cu(OTf)(2) to obtain conductivity up to 1.94 S/m. Notably, the electromagnetic interference (EMI) shielding effectiveness (SE) of the composite films in the X-band was 23.8 dB at a thickness of 1.1 mm, which was the best value obtained so far for conjugated polymers in thermoset systems, even better than that of epoxy composites containing carbon nanofillers. Due to the proper conductivity and interconnected nanofiber conductive network, this composite film showed a high absorption-dominated EMI shielding performance (absorption coefficient A = 0.71). This work demonstrates a promising strategy to prepare organic semiconductor composite films, which is expected to be applied to the preparation of absorption dominated electromagnetic shielding films and high-performance thermoelectric devices.