Synthesis of P3HT-b-PS donor-acceptor diblock copolymer carrying pendant fullerenes at precise positions along the PS block

• Synthesis of well-defined block copolymer P3HT-b-PS, carrying pendant fullerenes at the PS block.
• C60 moieties were grafted at precise positions along the PS block through a Diels-Alder cycloaddition.
• The control grafting of acceptor entities along the insulating block of conjugated copolymer opens new avenues of morphologies where the aggregation/ crystallization could be controlled/tailored.

We present a strategy for the synthesis of a well-defined rod-coil block copolymers of regioregular poly(3-hexylthiophene) and polystyrene (P3HT-b-PS), carrying pendant fullerenes (C60) at precise positions along the PS block. The synthesis is achieved by combining ‘living’ anionic polymerization, Kumada catalyst-transfer polycondensation, and click chemistry. Azide terminated polystyrene was synthesized via anionic polymerization, while C60 moieties were grafted along the coil block with a [4+2] Diels-Alder cycloaddition reaction. The regioregular poly(3-hexylthiophene) rod donor block was end-capped with alkyne and was coupled with the azide terminated polystyrene via a copper catalyzed alkyne-azide cycloaddition. Size exclusion chromatography (SEC), NMR, and FT-IR spectroscopies were employed to confirm the synthesis of the diblock copolymers. Furthermore, the end-capping of the ‘living’ polystyrene (PS) with the diphenylethylene cyclobutene (DPE-CB) end-group was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). Thermogravimetric analysis (TGA) was employed for the estimation of the C60 content in the block copolymer. The C60 content at the coil block was 22 wt% and a strong quenching of photoluminescence (PL) was observed as the result of a large interfacial area between the P3HT and C60 in the diblock copolymer. The bonding of C60 across the PS block offers new routes to engineering stable morphologies, where the degree of organization/aggregation and/or crystallization of the acceptor material, of paramount importance for stable and efficient electron transport, may be controlled.

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