Self-assembly of a poly(phenyleneethynylene) on multiwall carbon nanotubes: Correlation of structural and optoelectronic properties towards solar cells application

In this work, we report on the preparation of processable nanocomposites of multiwall carbon nanotubes (MWCNTs) and a conjugated copolymer, hereafter called pPET3OC12-sqS bearing a phenyleneethynylene trimer and a dithio disulfide moiety. This specific alternation of rigid and flexible units allows selfassembly of the conjugated backbone on the nanotubes wall through pi-pi interactions, without affecting the effective conjugation length of the polymer as found by (HNMR)-H-1, UV-Vis and fluorescence spectroscopy. The flexible sequences favour the stabilization of the composite by wrapping the MWCNTs wall as observed by electron transmission microscopy. As a result of this supramolecular arrangement, the absorption and emission maxima of the polymer are maintained but a quenching from 0.55 to 0.27 of the polymer fluorescence is found, which likely arises from efficient photoinduced electron transfer from the pPET30C12-sqS to the MWCNTs. The incorporation of the nanotubes in the polymer matrix increases the electrical conductivity of the thin films in one order of magnitude and lowers the LUMO value, opening the possibility of a future application of the composite as electron acceptor material in organic photovoltaic devices. (C) 2020 Elsevier B.V. All rights reserved.