![]() ![]() This is superior to those of PDPP3T with just alkyl chains and PDPP3T-2. As a result, the thin film of PDPP3T-1 exhibits high saturated hole mobility up to 2.6 cm(2) more » V-1 s(-1) without any post-treatment. Polymer chains of PDPP3T-1 in which TEG chains are uniformly distributed can self-assemble spontaneously into a more ordered thin film. It is demonstrated that the incorporation of TEG chains has a significant effect on the interchain packing and thin-film morphology with noticeable effect on charge transport. Two new diketopyrrolopyrrole (DPP)-terthiophene-based conjugated polymers PDPP3T-1 and PDPP3T-2, with both hydrophilic triethylene glycol (TEG) and hydrophobic alkyl chains, are reported. Side chain engineering of conjugated donor-acceptor polymers is a new way to manipulate their optoelectronic properties. The improved stretchability of the polymers is attributed to both the presence of soft amorphous regions and the intrinsic packing arrangement of its crystalline domains. In conclusion, it is also observed that the molecular packing orientations (either edge-on or face-on) significantly affect the mechanical compliance of the polymer films. Furthermore, this polymer exhibits a hole mobility of 0.1 cm2 V -1 s -1 even at 100% strain or after recovered from strain, which reveals prominent continuity and viscoelasticity of the polymer thin film. It is observed that the fused thiophene diketopyrrolopyrrole-based polymer, when incorporated with branched side chains and an additional thiophene spacer in the backbone, exhibits improved mechanical endurance and, in addition, does not show crack propagation more » until 40% strain. Structure–property relationships (especially in both side chain and backbone engineering) are investigated for a series of poly(tetrathienoacene-diketopyrrolopyrrole) polymers. Understanding the distribution and behavior of both crystalline domains and amorphous regions in conjugated polymer films, upon an applied stress, shall provide general guiding principles to design stretchable organic semiconductors. The design of polymer semiconductors possessing high charge transport performance, coupled with good ductility, remains a challenge. more » This facile method gives insights into the physical nature of amorphous phases in conjugated polymers for better revealing their structure-property relationships, which will guide the designs of new materials with optimized electrical and mechanical properties in the future. Furthermore, the weight fractions of MAF and RAF with various film thicknesses are qualitatively analyzed based on the heat capacity step of each amorphous fraction during the glass transition. ![]() The Tgs of diketopyrrolopyrrole-based conjugated polymer thin films are also identified by the same method, with both Tgs showing a decreased value compared to those of bulk samples. Tgs of MAF and RAF increase and decrease with increasing size of fused thiophene units in the backbone, respectively. The detected relaxations were interpreted, in agreement with existing observations in similar systems, as a side-chain relaxation (low temperature), mobile amorphous fractions (MAF), and rigid amorphous fractions (RAF). In this work, alternating current (ac) chip calorimetry and flash differential scanning calorimetry (flash DSC) are applied to successfully identify the Tgs and segmental relaxations of conjugated polymers. Despite some well-developed methods that exist for detecting Tg of conjugated polymers, there is still a need for the combination of advanced calorimetric methodologies to characterize Tg in a broad range of temperatures and scales from bulk to nanometer-thin films. The glass transition temperature (Tg) of conjugated polymers is a crucial physical parameter that governs their mechanical and electrical properties for applications from sensor technology to skin-like electronics. ![]()
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