A CALORIMETRIC STUDY OF THE PHASE-TRANSITIONS IN POLY(3-HEXYLTHIOPHENE)

Differential scanning calorimetry was utilized for investigating the i sothermal crystallization of a poly(3-hexylthiophene) (P3HT) sample ov er a wide range of temperatures. We found two well separated crystal f ormation processes: a fast process, essentially completed before the s ample reaches the isothermal conditions, which produces crystals havin g higher transition temperatures (at around 178 degrees C), and a slow process which leads to continuous growth of less stable crystals, the transition temperatures of which are determined by the crystallizatio n temperature, namely, about 32 degrees C above. The slow crystallizat ion process occurs at temperatures as low as 40 degrees C. This crysta llization behaviour supports the suggestion that a nematic stale exist s in the melt of P3HT.