Side-Chain Length Dependence of Young’s Modulus and Strength in Crystalline Poly(3-alkylthiophene) Nanofibers

Abstract

Understanding the side-chain effect on the mechanical properties of conjugated-polymer nanocrystals is critical for the design of high-performance soft electronic devices. However, due to the complexity of the side-chain effect and hierarchical structure in bulk materials, the classical macroscopic characterizations mask the mechanical properties of nanocrystals. Here, we have measured the mechanical properties of crystalline poly­(3-alkylthiophene) (P3AT) nanofibers with different side-chain lengths (with 4, 6, 8, 10, and12 alkyl carbons per side chain) by the combination of thermal shape fluctuation analysis and single-molecule force spectroscopy (SMFS). We found that poly­(3-hexylthiophene) (P3HT, with 6 alkyl carbons) nanofibers exhibit a higher Young’s modulus and strength than poly­(3-butylthiophene) (P3BT, with 4 alkyl carbons), poly­(3-octylthiophene) (P3OT, with 8 alkyl carbons), poly­(3-decylthiophene) (P3DT, with 10 alkyl carbons), and poly­(3-dodecylthiophene) (P3DDT, with 12 alkyl carbons) nanofibers. Furthermore, we illustrated that the more pronounced J-aggregate in P3HT nanofibers increases the probability of the one-step unfolding in SMFS experiments producing high strength and high Young’s modulus. The effects of the regioregularity of the polymer chain and the width of the nanofiber on the Young’s modulus of P3AT nanofibers were also investigated. Our results explain how the side-chain length affects the nanomechanical properties of P3AT nanofibers and deepen our understanding of the relationship between the chemical composition and nanomechanical properties of conjugated polymers.

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

“…However, AFM experiments by Jiang et al investigating the unfolding behavior of P3AT chains show that a single P3OT chain can extend further than a single P3DT chain (ΔL of ∼14 nm compared to ∼12 nm). 117 Likewise, buckling experiments by Printz et al suggest that both the fracture strain and yield point of P3OT are greater than that of P3DDT (n = 12). 60 Thus, previous literature suggests that the decrease in fracture strain from n = 8 to n = 10 cannot solely be explained here by differences in degree of polymerization.…”

Study on the regulation of polythiophene whiskers by electric field induction and the anisotropy of the film surface

“…As shown in Fig. 7, the UV absorbance peaks at wavelengths of 614, 566 and 526 nm are attributed to the characteristic absorption lines of 0-0, 0-1 and 0-2 vibronic transitions respectively in the aggregated P3HT, 44 the intensities of which decrease regularly with increase of treatment time. This may be due to P3HT whisker aggregates assembling to form fibers after the induction of the electric field, and the solution becomes clear, resulting in a decrease in its absorbance.…”

Manipulation of a Single Polymer Chain: From the Nanomechanical Properties to Dynamic Structure Evolution

“…Although SMFS has been proven to be quite useful in correlating the microstructure (or conformation) of polymers and their dynamic structure evolution with the nanomechanical properties and biofunctions, there are still many problems that need to be solved in order to further deepen our understanding in the real material and biological systems. In the materials system, although we have explored the nanomechanical properties in polymer single crystal and nanocomposite, there is still quite some distance, in terms of system complexity, between the polymer single crystal system and the real polymer material systems, such as polymer fiber and ultrathin polymer film, 137 which contain both crystal and amorphous phases. However, previous studies on the single crystal have produced many useful force fingerprints that laid a solid foundation for us to further study the effect of the amorphous phase on the nanomechanical properties of polymer crystals.…”