The effects of different alkyl substitution on the structures and properties of poly(3-alkylthiophenes)

In order to investigate the influence of different alkyl side chain substit ution on the structures and properties of P3ATs, X-ray diffraction, differe ntial scanning calorimetry (DSC), thermal gravity analysis (TGA), Fourier t ransform infrared spectra (FTIR) and ultraviolet-visible spectra (W-VIS) we re applied to characterizing the samples of ploy(3-octylthiophene) (P3OT), poly(3-dodecylthiophene) (P3DDT) and poly(3-octadecylthiophene) (P3ODT). It is found that the different length of alkyl group substitution leads to gr eat difference in molecular chain packings, according to the room temperatu re X-ray diffraction results. The temperature dependence of X-ray diffracti on experiments were also performed to study the melting processes of P3ATs. With the increase in the number of carbon atoms in alkyl side chains, the melting point decreases, and the thermal stability decreases too. The resul ts of both FTIR and W-VIS spectra indicate that the conjugation length of P 3DDT is the longest. among the three P3ATs. (C) 2001 Elsevier Science B.V. All rights reserved.