LAUSR

The cloud-point curves for solutions of regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) in o-dichlorobenzene as a function of composition were measured using a thermooptical analysis method. The binary polymer solution shows phase equilibria between a single coiled polymer in solution and polymer in nanocrystalline aggregation, in which the coexistence points at the melting temperature (i.e., solid–liquid equilibria) could be described by the theory of melting point depression combined with the Flory–Huggins model. Through the correlation of theory and experimental data, the heat of fusion per crystalline repeat unit (ΔHu = 47.5 J/g) and the binary interaction parameter (χ = 32.6/T) were estimated. When the solutions were further characterized using UV–vis spectroscopy and X-ray diffraction (XRD), the absorption spectra showed a red-shift (λmax = 464 to 518 nm) with increasing P3HT concentration from 0.01 to 6 wt %, and the XRD data displayed a trace of (100) peaks at 2θ = 5.39° with d-spacing of 1.6 ...