Regioregular Alternating Polychalcogenophenes-Block-Poly(3-hexylthiophene): Synthesis, Structural Characterizations, Molecular Properties, and Transistors.

Sequence-controlled polychalcogenophenes have attracted considerable attention in polymer science, particularly in terms of their synthesis, structure, and functionality. In this work, we designed a new series of alternating block conjugated copolymers, denoted as poly(alt-AB)b(3HT), where one block consists of an alternating copolymer and the other is poly(3-hexylthiophene) (P3HT). To construct three sequence-controlled polychalcogenophenes, we utilized 3-hexylthiophene (S), 3-hexylselenophene (Se), and 3-hexyltellurophene (Te) as A and B units, yielding P(SSe)b(3HT), P(STe)b(3HT), and P(SeTe)b(3HT), respectively. These polymers were synthesized via nickel-catalyzed Kumada polymerization by sequentially introducing two different Grignard monomers. Through catalyst-transfer polycondensation (CTP), we achieved precise control over molecular weight, dispersity, block length, and main chain sequence. The polymer structures with high side chain regioregularity in both blocks were definitively confirmed using ¹H and ¹C NMR analyses. Grazing-incidence wide-angle X-ray scattering (GIWAXS) revealed that all polymers predominantly adopt an edge-on orientation in the solid state. In organic field-effect transistor (OFET) measurements, P(SSe)b(3HT) exhibited the highest hole mobility of 4.4 × 10⁻ cm V⁻¹ s⁻¹, attributed to its highly ordered molecular packing in thin films. Notably, P(STe)b(3HT) achieved a hole mobility of 2.9 × 10⁻ cm V⁻¹ s⁻¹, among the highest reported for tellurophene-containing polychalcogenophenes.