Preparation and characterization of new poly-pyrrole having side chain liquid crystalline moieties

Abstract

We have synthesized a novel liquid-crystalline (LC)-conducting polymer by introducing LC group into pyrrole monomer and polymerizing it with FeCl 3. The N-substituted pyrrole with LC group (Py-RedII) was prepared by direct reaction of potassium pyrrole salt with 2-[ N-ethyl- N-[4-[(4-nitrophenyl)azo]-phenyl]amino]ethyl-3-chloropropionate (RedII). The polymerization of this monomer was successful, giving a conjugated polymer system with liquid crystalline moieties in moderate yield. The polymer obtained was soluble in organic solvents and had a thermotropic liquid crystallinity with mosaic texture characterized by polarizing optical microscopy. Phase transitions, thermal analysis and rheological studies were also evaluated by means of differential scanning calorimetry (DSC), thermogravimetry analysis (TGA) and scanning electron microscopy (SEM), respectively. Spectral properties of poly (2-[ N-ethyl- N-[4-[(nitrophenyl)azo]phenyl]amino]ethyl- N-pyrrolyl propionate) (PPy-RedII) were characterized by UV, IR, 1H NMR, and 13C NMR spectroscopies. The photoluminescence spectrum of the film showed that maximum photoluminescence peak emission is located at 437 nm, corresponding to the photon energy of 2.5 eV. Electrical conductivity of PPy-RedII was studied by the four-probe method and produced a conductivity of 7.5 × 10 − 4 S cm − 1 .