Dynamic\nInteractions between Poly(3-hexylthiophene)\nand Single-Walled Carbon Nanotubes in Marginal Solvent

Abstract

Interfacial interactions between\nconjugated polymers and carbon\nnanotubes are pivotal in determining the device performance of nanotube-based\npolymer electronic devices. Here, we report on interfacial structures\nand crystallization kinetics of poly­(3-hexylthiophene) (P3HT) in the\npresence of single-walled carbon nanotubes (SWNTs) in anisole by means\nof transmission electron microscope (TEM) and ultraviolet–visible\n(UV–vis) absorption spectroscopy. Confined on SWNT surfaces,\nthe P3HT forms nanofibril crystals perpendicular to the long axis\nof SWNTs. The equilibrium dissolution temperature of the P3HT crystals\nin anisole is determined to be 381 ± 10 K according to the Hoffman–Weeks\nextrapolation approach. Upon cooling, the polymer solution spontaneously\nundergoes a time-dependent chromism. Various kinetics factors such\nas crystallization temperature, concentration, and SWNT loading have\nbeen investigated. It is found that the growth rate (<i>G</i>) of the crystals scales with concentration (<i>C</i>)\nas <i>G</i> ∝ <i>C</i>^1.70±0.16. The Avrami model is utilized to analyze the nucleation mechanism\nand the Avrami exponents vary between 1.0 and 1.3. The Lauritzen–Hoffman\ntheory is applied to study the chain-folding process. The fold surface\nfree energy is calculated to be (5.28–11.9) × 10^–2 J m^–2. It is evident that the addition of 0.30\nwt % SWNTs reduces the fold surface free energy by 55.6%.