The Short-Range Ordered Aggregation Structures Obtained by Controlling the Chain Segment Movement for Stretchable IDTBT Films

A continuous network with short-range aggregation structures in an amorphous matrix is widely recognized for achieving optimal electronic and mechanical performance of conjugated polymer films. The size and structural order of these aggregates critically determine the ability to accommodate and dissipate strain without disrupting the charge transport pathways. Here, we systematically investigated the effect of polymer chain dynamics on the evolution of aggregation structure for the conjugated polymer poly(indacenodithiophene-co-benzothiadiazole) (IDTBT) by controlling the annealing temperature (Ta). In the as-cast film, the polymer backbone remains kinetically trapped in a distorted conformation, leading to a loosely packed and disordered morphology. Thermal annealing at 100 °C, between the backbone glass transition temperatures (Tg) and the disaggregation temperature (Tdisagg), activates the segment motion, enabling reorganization into small, short-range ordered aggregates with an extended conformation. When annealed at 260 °C (Ta > Tdisagg), full chain mobility permits assembly into larger, more ordered aggregates with dense molecular packing. Consequently, the charge mobility increases from 0.92 cm2 V–1 s–1 in the as-cast film to 3.14 cm2 V–1 s–1 after annealing at 260 °C. Under strain, the film annealed at 100 °C retains its short-range aggregates, which facilitates efficient stress dissipation through interlayer slip and preserves charge mobility. In contrast, the film annealed at 260 °C exhibits premature fracture of the large ordered aggregates accompanied by restricted chain alignment. As a result, the film annealed at 100 °C maintains a charge mobility of 0.86 cm2 V–1 s–1 under 100% strain, whereas the 260 °C-annealed film exhibits a substantially lower mobility of 0.14 cm2 V–1 s–1. These results underscore the critical role of short-range aggregation structures in achieving high-performance stretchable conjugated polymer films.