Polymer Chain Segmental Motion Enhanced Charge Transport and Strain Energy Dissipation in Stretchable Conjugated Polymer Films

The deformation mechanisms of stretchable conjugated polymer films are critical for their electrical performance in wearable electronics. However, the effect of polymer chain motions on their deformation mechanisms remains underexplored. Herein, we propose that polymer segmental motion facilitates chain conformational changes under strain, thereby establishing efficient charge transport pathways in stretched films. This hypothesis is enabled by systematically examining the uniaxial stretching behavior of a high-mobility conjugated polymer, IDTBT, at varying temperatures. When the film is heated to 70 °C (near its glass transition temperature, T g ), the segmental movement of the mainchains is substantially activated, providing sufficient free volume for chain rearrangement. Upon stretching to 50%, backbone planarization occurs, as evidenced by an increase in the I BT / I IDT Raman ratio from 2.42 to 2.80, accompanied by improved chain alignment with a high dichroic ratio of 1.37. Meanwhile, chain disentanglement and crystallite reorientation are facilitated by enhanced chain diffusion and slippage. Further stretching to 100% strain induces the self-assembly of adjacent stretched chains in the amorphous region into ordered aggregates/crystallites, leading to an approximate 2-fold increase in the relative degree of crystallinity. The reconstructed intra- and interchain transport pathways effectively enhance charge mobility, reaching 1.11 cm 2 V –1 s –1 even under 100% strain. In contrast, stretching the film at 25 °C (well below T g ) to 100% strain, segmental motion remains restricted. This leads to pronounced cavitation and microcracking through chain scission and crystallite fragmentation, sharply reducing charge mobility from 0.82 to 0.48 cm 2 V –1 s –1 . When stretched at 90 °C (above T g ), dramatic polymer motions reduce backbone planarity and crystallinity, yielding a moderate charge mobility of 0.89 cm 2 V –1 s –1 at 100% strain. These results offer valuable insights for optimizing molecular design and operating conditions of conjugated polymers in wearable electronics.