Role of the Middle Block on Crystallization-Driven Self-Assembly of ABC Copolymers Containing the Crystalline π-Conjugated Polythiophene End Block

Modulation of microstructures of copolymers containing π-conjugated poly(3-hexylthiophene) (P3HT) is important due to the close connection between their structures and optoelectronic properties. Crystallization-driven self-assembly of copolymers containing P3HT in solution leads to the formation of regular nano-objects and facilitates their applications. In this work, we prepared a series of polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) (PI-b-PS-b-P3HT) triblock copolymers with relatively fixed degree of polymerization (DP) of PI and P3HT blocks, while varying the DP of middle PS block, via the coupling reaction between monoaldehyde end-functionalized P3HT-H/CHO and living anionic PI-b-PS–Li+ species. The self-assembly behavior of triblock copolymers was comprehensively studied by varying the parameters of DPPS, annealing temperatures, and solvents. The cooperative self-assembly between different copolymers was also achieved. As the PS block has a changeable solvation or plasticization ability depending on these parameters, the rearrangement or recrystallization of P3HT and the self-assembly process could be modulated accordingly. A library of nano-objects, including the uniform fibers, as well as the rarely reported spheres, zipper-like fibers, block-like fibers, and bead-like fibers, were captured. This work confirmed that the middle PS block played a prominent role in the modulation function on the self-assembly behavior of PI-b-PS-b-P3HT triblock copolymers, greatly enriching the microstructures of π-conjugated copolymers.