Abstract :
In order to investigate the effect of the bulky pendant group and the spacer length between
the pendant group and polythiophene main chain on the optical property of polythiophene
backbone, a series of polythiophene derivatives were synthesized via copolymerization of
3-hexylthiophene with four different types of 4-((4-(phenyl)azo)phenoxy)alkyl-3-
thienylacetate. The alkyl spacers with different lengths, i.e., butyl, hexyl, octyl and undecyl
groups were used between the bulky azobenzene group and the thiophene ring. The
compositions and structures of these polythiophene derivatives were characterized. The
structural dependence of thermochromic behaviour of these copolymers were
systematically studied and results compared with poly(3-hexylthiophene) (P3HeT). A
thermochromic temperature coefficient (CTC) was defined for the first time in an attempt to
quantitatively compare the sensitivity of the thermochromism in the copolymers. The
results have shown that these copolymers with a bulky azobenzene group in side chain
have a higher (CTC) value than P3HT and the CTC value of the copolymers increase with
increasing the spacer length. C 2005 Springer Science + Business Media, Inc.
