One dimensional main-chain crystallization kinetics of poly(3-octylthiophenes) investigated by infrared spectroscopy

Time-resolved infrared spectroscopy has been used to study the melt crystallization behavior of poly(3-octylthiophenes) (P3OT), which is a typical conductive polymer among the family of poly(3-alkylthiophenes) (P3ATs). It is found that, during the isothermal crystallization process at high temperature, the alkyl side chains of P3OT always keep in disordered state, whereas the ordering packing of conjugated backbone takes place. In order to reveal the structural changes and the crystallization kinetics corresponding to the main-chain ordering process, two spectral regions that associated with π-π stacking and the effective conjugation length of P3OT have been analyzed in detail. The characteristic IR bands of crystalline and amorphous phase are identified in each spectral region. Moreover, a simple spectral method has been proposed to calculate the evolution of crystallinity during the isothermal crystallization process of P3OT. Of particular note, the distinct one-dimensional growth kinetic of P3OT crystal has been revealed by Avrami analysis.