Abstract
There were recent studies suggesting that nano-carbon materials could enhance the crystallinity development or the charge mobility of conjugated polymers. It is highly tempting to speculate that the enhanced charge mobility might be a result of morphological changes in the matrix polymer. By use of wide-angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC), here we report morphological development and crystallization kinetics of poly(3-hexylthiophene) (P3HT) filled with different nano-carbon materials such as single- and multi-walled carbon nanotubes (SWCNT/MWCNT), carbon nanocapsules (CNC) as well as [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The DSC results indicated that nano-carbon materials may generally enhance instantaneous nucleation, with SWCNT being most effective among the four nano-carbon fillers. WAXS results indicated clear increases of the crystalline domain size upon cooling for CNC composite. Both the classical Avrami equation and a modified version allowing parallel routes were adopted to describe the crystallization kinetics and to determine the corresponding kinetic parameters. For pristine P3HT, the classical Avrami exponent n ≈ 2, suggesting that the crystals are rod-like in shape, as confirmed with polarize optical microscopy (POM). For nano-carbon filled P3HT composites, the apparent value of n generally lies between 1 and 2, implying competing paths of crystallization. Using the modified Avrami equation, it is observed that the addition of the nano-carbon materials can decrease the apparent Avrami exponent n due to enhanced instantaneous nucleation, as indicated by the consistently increased the classical Avrami rate constant K due to increased nucleation density.