Influence of side‐chain isomerization on the isothermal crystallization kinetics of poly(3‐alkylthiophenes)

Abstract

Flexible alkyl side chain in conjugate polymers (CPs) improves the solubility and promotes solution processability, in addition, it affects interchain packing and charge mobilities. Despite the well-known charge mobility and morphology correlation for these semi-crystalline polymers, there is a lack of fundamental understanding of the impact of side chain on their crystallization kinetics. In the present work, isothermal crystallization of five poly(3alkylthiophene-2,5-diyl) (P3ATs) with different side-chain structures were systematically investigated. To suppress the extremely fast crystallization and trap the sample into amorphous glass, an advanced fast scanning chip calorimetry technique, which is able to quench the sample with few to tens thousands of K/s, was applied. Results show that the crystallization of P3ATs was greatly inhibited after incorporation of branched side chains, as indicated by a dramatic up to six orders of magnitude decrease in the crystallization rate. The suppressed crystallization of P3ATs were correlated with an increased π-π stacking distance due to unfavorable side-chain steric interaction. This work provides a pathway to use side-chain engineering to control the crystallization behavior for CPs, thus to control device performance.Xiaodan Gu earned his Ph.D. from the Department of Polymer Science and Engineering at the University of Massachusetts Amherst, advised by Prof. Thomas P. Russell, focusing on the self-assembly of block copolymers and their lithographic applications. Subsequently, he started a post-doctoral appointment co-advised by Zhenan Bao and Michael F. Toney at Stanford University and SLAC National Accelerator Laboratory, where he studied the morphology of roll-to-roll printed electronics using real-time X-ray scattering techniques. He moved to the University of Southern Mississippi to start his independent career in 2016. His current research interests revolve around various fundamental polymer physics phenomena related to conjugated polymers and their derivative devices. His group studies structure, dynamic, and morphology of conjugated polymers and aim to link their molecular structures to their macroscopic properties through advanced metrology with an emphasis on scattering techniques. He was awarded ORAU Powe Junior Faculty Enhancement Award in 2019, ACS PMSE Young investigator, and a contributor to "Young Talents" special issue to Macromolecular Rapid Communications, "Emerging investigator" for 2020 Polymer Chemistry, and " Early Career Scholars" for 2021 Journal of Materials Research from MRS.

Adhesive Properties of Semiconducting Polymers: Poly(3-alkylthiophene) as an Ersatz Glue

“…113,114 However, the usual result of an increase in the alkyl chain length is to increase the lamellar spacing 115 and to decrease the π−π stacking. 67,69,116 These effects suggest a weakening of van der Waals forces between polymer chains. Whereas the parameters associated with elasticity exhibited monotonic relationships with the length of the alkyl side chain (Figure 2a−d), those associated with plasticity�namely fracture strain and toughness (Figure 2e,f), exhibited maxima.…”

Novel benzo[b]thieno[2,3-d]thiophene derivatives with an additional alkyl-thiophene core: synthesis, characterization, and p-type thin film transistor performance

“…67–69 When comparing compounds 2 and 3 , compound 2 presented lower melting temperature than 3 , possibly due to the smaller configuration entropy of the corresponding compound via the branched side chain. 70,71…”

“…[67][68][69] When comparing compounds 2 and 3, compound 2 presented lower melting temperature than 3, possibly due to the smaller configuration entropy of the corresponding compound via the branched side chain. 70,71 In the case of optical properties of each BTT derivative, UV-vis measurements were implemented. The maximum absorption wavelengths (l max ) of compounds 1-3 were 434, 437, and 448 nm, respectively (Fig.…”

Side-Chain Engineering of Conjugated Polymers for High-Performance Organic Field-Effect Transistors

“…Many studies demonstrate that enhancing the lamellar stacking enlarges the packing domains, and thus large ordered regions are formed. − In addition, different side-chains modulate the thin-film microstructures, including packing mode (edge-on, face-on, etc . ), domain size, and paracrystallinity, and affect the overlapping π-orbitals, π–π stacking distance, and d -spacing along the backbone direction corresponding to the skeleton conformation. − ,− Therefore, the charge mobilities can be tailored by side-chain engineering strategies.…”

“…20 Gu et al used fast scanning chip calorimetry and investigated the isothermal crystallization behavior of P3HT, P3(4MP)T, P3(3MP)T, P3(2MP)T, and P3(2EB)T (Scheme 1). 27 These polymers contained linear and branched side-chains but the same main-chain. Interestingly, the crystallization rates decreased six-time after incorporating branched side-chains, correlated with the increase in π−π stacking distance (P3HT, 3.71 Å; P3(2EB)T, 4.43 Å).…”