Stabilizing bicontinuous nanophase segregation in piCP-C60 donor-acceptor blends

Abstract

The synthesis and thin film properties of a conjugated polymer bearing graft chains that are compatible with a fullerene, chemically modified with a similar motif, are described. The graft copolymer, obtained by nitroxide-mediated radical polymerization of a vinyl triazole onto a postfunctionalized poly(3-hexylthiophene) (P3HT) backbone, is blended with a fullerene modified with a pendant triazole functionality (TAZC60). For a given ratio of polymer:TAZC60, graft copolymer (P3HT-g-PVTAZ:TAZC60) blends exhibit substantially reduced photoluminescence compared to P3HT:TAZC60 blends, while TEM analysis reveals the graft polymer undergoes extensive mixing with the fullerene to form bicontinuous 10 nm phase domains. Graft polymer blends annealed for 1 h at 140 degrees C retain their nanometer phase separation as evidenced by TEM, UV-vis, XRD, and photoluminescence analysis, and phase purity was enhanced. In contrast, P3HT:TAZC60 blends exhibit micron-sized phase-segregated morphologies before and after annealing. The chemical similarity of the triazole functionality attached to P3HT and the fullerene leads to the formation of films with uniform, stable, nanophase morphologies. This strategy may prove a useful strategy for controlling the extent of phase segregation in electron donor and acceptor blends of pi-conjugated polymers (piCPs) and fullerenes.