Measuring Order in Regioregular Poly(3-hexylthiophene) with Solid-State 13C CPMAS NMR.

Abstract

We report on measurements of order in semicrystalline, high molar mass poly(3-hexylthiophene) (P3HT) by solid-state 13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) measurements. The relative degree of crystallinity was estimated for two films with different drying conditions via X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Order determined by 13C NMR does not necessarily correlate with crystallinity, indicating that local order can occur in noncrystalline regions. Slow main chain dynamics influence the 13C NMR peak widths at lower temperatures (<0 °C), with side chain motions influencing the main chain motions. At higher temperatures (>0 °C), where narrower thiophene resonances are observed, these main chain conformation rearrangements occur on fast time scales (≪3 ms). This room-temperature dynamic disorder suggests that P3HT may be classified as a conformationally disordered (CONDIS) crystal.