Vol. 8(32), pp. 1611-1622, 30 August, 2013 DOI: 10.5897/IJPS12.107 ISSN 1992 - 1950 © 2013 Academic Journals http://www.academicjournals.org/IJPS International Journal of Physical Sciences Full Length Research Paper Synthesis and characterization of polyindole with liquid crystalline azobenzene as side chains Seyed Hossein Hosseini 1 * and Maryam Ashjari 2 1 Department of Chemistry, Faculty of Science, Islamic Azad University, Islamshahr Branch, Tehran-Iran. 2 Department of Chemistry, Faculty of Science and Engineering, Islamic Azad University, Saveh Branch, Saveh-Iran. Accepted 8 August, 2013 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 ---    -       -        --   ----- - (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, 1 H, 13 C-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-   g    : C→ S A (161°C), S A → 18°C  → 1°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. INTRODUCTION Conjugated polymers are well-known for their excellent electrical conductivities in oxidized (doped) state. The recent development of processable conducting polymers has opened the way for large-scale industrial applications. Conjugated polymers have been used widely in many areas such as rechargeable batteries (Heinze, 1991; Roth and Graupher, 1993), condensators (Mohammadi et al., 1986), diodes (Turut and Koleli, 1993; Kolelil et al., 1994), and sensors (Hosseini et al., 2005, 2006). Among these classes of polymers, polyaniline, polypyrrole, polythiophene, etc. have been studied extensively because of their favorable processability and relative stability (MacDiarmid, 1997; Hosseini and Entezami, 2001, 2003). Heteroaromatic molecules containing nitrogen have very interesting properties. Polyindole is an electro active polymer, which can be obtained from electrochemical oxidation of indole or chemical oxidation using FeCl 3 or CuCl 2 (Xu et al., 2006). However, only little investigations have been made on chemically synthesized polyindole (John and *Corresponding author. E-mail: shhosseini@iiau.ac.ir, Tel: +98(9121374816).