Phase Separation in the Melt and Confined Crystallization as the Key to Well-Ordered Microphase Separated Donor–Acceptor Block Copolymers

Microphase-separated donor–acceptor block copolymers have been discussed as ideal systems for morphology control in organic photovoltaics. Typical microphases as known from coil–coil systems were not observed in such systems due to crystallization dominating over microphase separation. We show how this problem can be overcome by the synthesis of high molecular weight block copolymers leading to a high enough χN parameter and microphase separation in the melt. A combination of copper-catalyzed azide-alkyne click reaction and nitroxide mediated radical polymerization (NMRP) was used for the synthesis of donor–acceptor poly(3-hexylthiophene)-block-poly perylene bisimide acrylate (P3HT-b-PPerAcr) block copolymers. With this synthetic strategy, high molecular weights are possible and no triblock copolymer byproducts are formed, as observed with former methods. Two different block copolymers with a high molecular weight P3HT block of 19.7 kg/mol and a PPerAcr content of 47 and 64 wt % were obtained. X-ray scatt...