Improving Mobility–Stretchability Properties of Polythiophene Derivatives through Ester-Substituted, Biaxially Extended Conjugated Side Chains

Abstract

P3HT, as one of the most important conjugated polymers, has been reported to possess low mobility and poor stretchability. In this study, two polythiophenes are prepared by attaching ester-substituted, biaxially extended conjugated side chains with backbones of 3-(thiophen-2-yl)-6-(thiophen-3-yl)thieno-[3,2-b]thiophene-bithiophene (PDCTT2T) and 3-(thiophen-2-yl)-6-(thiophen-3-yl)thieno[3,2-b]thiophene-difluorobithiophene (PDCTT2T-F) and compared with their respective counterparts without the biaxially extended side chains (thieno[3,2b]thiophene-bithiophene and thieno[3,2-b]thiophene-difluorobithiophene backbonesfor PDCTT and PDCTT-F). Through investigating mobility−stretchability properties of these four polymers, the synergetic effect of ester-substituted, biaxially extended conjugation and backbone fluorination is demonstrated to improve mobility−stretchability properties of polythiophenes, especially in a highly stretched state. On the one hand, the biaxially extended side chains implant a more amorphous structure and reinforce the intramolecular charge transfer between polymer backbones. On the other hand, the backbone fluorination confers to a rigidified polymer backbone, facilitating effective intrachain charge transport. As a result, PDCTT2T-F delivers superior mobility (0.20 cm 2 V −1 s −1 ) to PDCTT-F (0.054 cm 2 V −1 s −1 ) alongside 11 times higher mobility retention at a 100% strain. In addition, both PDCTT2T and PDCTT2T-F encouragingly retain decent mobility throughout 800 stretching−releasing cycles (at a 60% strain), outperforming their respective parent polymers without side-chain conjugation that show a one-order decrease in mobility. The results shown in this work signify an effective design strategy to fine-tune mobility−stretchability properties of polythiophenes.

Recent Progress in Conducting Polymer Composite/Nanofiber-Based Strain and Pressure Sensors

“…Another method to improve the air stability is to employ the ester-substituted side chains with more free space. This ester side chain substitution biaxially extends the conjugation to improve the mobility and stretchability attributed to the enhanced amorphous structure with reinforcements [164]. Interestingly, the crystallite orientation during the drawing process is mandatory in deciding the electrical conductivity.…”

Strain-insensitive naphthalene-diimide-based conjugated polymers through sequential regularity control

“…To study the mobilitystretchability property of the PNDI2T film, a film transfer technique was applied according to the method reported in the literatures. 26,27 Briefly, a transferred/stretched film was prepared in a nitrogen-filled glove box by transferring the PNDI2T film onto an elastomeric poly(dimethylsiloxane) (PDMS) slab, and then the PNDI2T film supported by the PDMS slab was stretched and transferred back to the wafer substrate. Note that the film transfer process was conducted at 70 1C.…”

“…The experimental procedure is described in the ESI † and reported in previous work. 27 The OM and AFM morphologies of the transferred/ stretched films are presented in Fig. 3a and b.…”

“…20 To improve the mobility-stretchability properties of n-type CPs without sacrificing their thermal and mechanical integrity, structural engineering should be used to maintain strength while improving the fracture strain of CPs. 21 The feasible approaches to structural engineering can be divided into three categories: (1) random copolymerization with dimensionally similar monomers, 22,23 (2) adoption of rigid fused-ring backbones for a near-amorphous structure, 24,25 and (3) introduction of conjugated side groups on the side chains to promote chain aggregation 26,27 or the combination of a fused-ring backbone and conjugated side groups. 28 Most of the methods capable of improving mobility-stretchability properties are applicable mainly to p-type CPs and are seldom reported in n-type CPs owing to the instability of carrier transport and limited types of backbones.…”

Enhancing the Memory-Stretchability Property of π-Conjugated Polymers Using Pendant Arene Side Chains in Nonvolatile Transistor Memory

“…However, there are still few designs on conjugated copolymers with charge-storage capability using side-chain engineering. Furthermore, the solid-state stacking, thin-film morphology, and mechanical property can be simultaneously improved by various side-chain engineering such as asymmetric design, , hydrogen-bonding-containing side chains, , and biaxially extended conjugated side chains that have been proposed to enrich more amorphous domains while maintaining the strong aggregation between the polymer chains, which is conducive to improving the stretchability of semiconducting polymers. , Previously, we reported an approach to establish an FET memory with combined channel and electret using a conjugated polymer with a pyrene-incorporated side chain . The pyrene moiety was understood to serve as the electron-trapping site, and its charge-storage/transport performance was optimized with the optimal pyrene content.…”