Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (04): 971-980.doi: 10.3866/PKU.WHXB20100409

• PHOTOCHEMISTRY AND SPECTROSCOPY • Previous Articles     Next Articles

Synthesis and Helical Conformation of New Optically Active Liquid Crystalline Polythiophene Containing Cyanoterphenyl Mesogen Pendant

CHEN Lie, CHEN Yi-Wang, YAO Kai, ZHOU Wei-Hua, LI Fan, NIE Hua-Rong   

  1. Institute of Polymers, Department of Chemistry, Nanchang University, Nanchang 330031, P. R. China
  • Received:2009-10-26 Revised:2009-12-16 Published:2010-04-02
  • Contact: CHEN Yi-Wang E-mail:ywchen@ncu.edu.cn

Abstract:

A novel liquid crystalline (LC) polythiophene bearing cyanoterphenyl mesogenic pendants with a long flexible spacer {—[thiophene—CH2—COO—(CH2)6—O—terphenyl—CN]n—, PT(6)TPhCN}was designedandsynthesized. Structures of the monomer and the polymer were characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy while the liquid crystalline and other properties were evaluated with thermo- gravimetry, differential scanning calorimetry (DSC), polarized optical microscopy (POM), ultraviolet visible (UV-Vis) spectroscopy, and photoluminescence (PL). The monomer shows enantiotropic smectic phases during the heating and cooling processes. Because of the long flexible spacer, the polymer PT(6)TPhCN exhibits a colorful SmAd mesogenic phase texture. The cyanoterphenyl group results in the polymer having good photoluminescence. The spacer length also greatly influences the UV absorption and photoluminescence behavior of the polymers. A longer spacer may better segregate the backbone, which effectively enhances the stronger photoluminescence emission. More interestingly, without introducing any chiral groups, the polymer exhibits an obvious Cotton effect on the circular dichroism (CD) spectra, which results from the predominant screw sense of the backbone. This is probably due to the heavy bulky mesogenic pendant rotating around the polythiophene backbone and producing a backbone with a helical conformation in the long wavelength region.

Key words: Photoluminescence, Liquid crystalline conjugated polymer, Cyanoterphenyl, Polythiophene, Helical conformation

MSC2000: 

  • O644