Abstract

In this study, a series of azobenzene-functionalized liquid crystalline (LC) polyindole derivatives: poly{2-[N-ethyl-N-[4-[4'-(nitrophenyl)azo]phenyl]amino]ethyl-3-indolyl acetate}, poly(In3AA-RedI), poly{2-[N-ethyl-N-[4-[4'-(nitrophenyl)azo]phenyl]amino]ethyl-3-indolyl acetate-co-indole}, poly(In3AA-RedI-co-In), poly{2-[N-ethyl-N-[4-[4'-(nitrophenyl)azo]phenyl] amino]ethyl-3-indolyl acetate-co-pyrrole},  and Poly(In3AA-RedI-co-py) were synthesized. Novel 3-substituted indole with liquid crystalline side chain (In3AA-RedI) was synthesized by the direct reaction of indole-3-acetic acid with 2-[N-ethyl-N-[4-[4́-(nitrophenyl)azo]phenyl] amino]ethanol (RedI). Chemical polymerization of (In3AA-RedI), and its copolymerization with indole and pyrrole were carried out by using ferric percholorate as oxidizing agent. The composition, structure and thermal property of these LC polyindole derivatives were fully characterized by FTIR, ¹H,¹³C-NMR and UV-Visible spectroscopic methods, and its LC behavior and photoresponsive property were also investigated by polarized optical microscope and differential scanning calorimetry (DSC). The results show that poly(In3AA-RedI) exhibited the smectic A (S_A) and nematic (N) liquid crystalline behavior. Conclusion shifted phase transition temperatures of the poly(In3AA-RedI) in the heating process  are as follows: C→ S_A (161°C),  S_A→N (184°C) and N→I (231°C). Electrical conductivity of polymer [poly(In3AA-RedI)] and two of its copolymers [poly(In3AA-RedI-co-In) and poly(In3AA-RedI-co-Py)], has been studied by four probe methods  and produced 8.3×10^-4, 6.4×10^-4 and 4.7×10^-3 Scm^-1 conductivities, respectively.

Key words: Conducting polymers, electrical conductivity, liquid crystalline polymer, optical properties, optical materials, polyindole.