Poly(3-hexylthiophene)-block-poly(tetrabutylammonium-4-styrenesulfonate) Block Copolymer Micelles for the Synthesis of Polymer Semiconductor Nanocomposites

We present the synthesis of a new amphiphilic poly(3-hexylthiophene)-block-poly(tetrabutylammonium-4-styrenesulfonate) (P3HT-b-PSS–/TBA+) block copolymer via polymer–polymer click reaction. The P3HT-alkyne block has a molecular weight of 17.6 kg/mol (SEC)/11.3 kg/mol (MALDI-ToF), and the block copolymer has a high purity due to the complete removal of both precursor blocks by a column chromatographic approach. The fluorinated styrenesulfonate polymer P(SS-CH2-CF3)-N3 is synthesized by reversible addition–fragmentation transfer (RAFT) polymerization, and a specific RAFT agent is used to avoid labile ester linkages. SEC with THF as solvent overestimates the molecular weight (MW) of P(SS-CH2-CF3)-N3, but 1H NMR spectroscopy allows for the exact calculation of the molecular weight. We show that the precursor block copolymer P3HT-b-P(SS-CH2-CF3) forms wormlike micelles by self-assembly with a crystalline P3HT core (diameter <30 nm) in polar solvents. In these BCP micelles the P(SS-CH2-CF3) precursor in the corona can be deprotected, and P3HT-b-PSS–/TBA+ micelles are formed. Additionally, the compartmentalized in situ synthesis of highly crystalline TiO2 (anatase) nanocrystals (<10 nm) stabilized within the PSS corona of the micelles is demonstrated. The resulting P3HT–TiO2 nanocomposites with well-defined nanoscale morphology are water-processable, and they are investigated in detail by cryo-TEM and UV–vis spectroscopy.