Aggregate dispersions to enhance the intrachain order in surfactant-stabilized aqueous colloids of poly(3-hexylthiophene)

Abstract

Aqueous colloids of conjugated polymers (CP), such as poly(3-hexylthiophene) (P3HT), are an attractive alternative for processing CP-based materials because (1) the microstructure of the conjugated polymers can be optimized during the formation of the colloid and (2) this method can significantly reduce the amount of hazardous organic solvents used during manufacturing. This investigation addresses the optimization of the polymer structure by studying the intrachain order of P3HT aggregates pre-assembled in mixtures of chloroform (CF) with dichloromethane (DCM) and subsequently dispersed in aqueous solutions of the surfactant sodium dodecyl sulfate (SDS) using a mini-emulsion method. Compared to an amorphous solution of P3HT, the observed intrachain order of P3HT in the colloids is much higher when using aggregate dispersions pre-assembled in the CF:DCM mixtures. Similar results are observed for aggregate dispersions of a benchmark organic photovoltaic system composed of P3HT and the fullerene derivative phenyl-C61-butyric acid methyl ester (PCBM), but in this case the intrachain order of P3HT in the P3HT:PCBM colloids is anomalously higher than the pure P3HT colloids. Atomic force microscopy (AFM) imaging reveals changes in the dominant structural motifs and morphology of the colloidal P3HT films, but not in a way that correlates with films processed from the aggregate dispersions.