Synthesis and Characterization of a Novel Dendronized Polymer Bearing Azobenzene Moieties in the Side Chain

Abstract

Novel dendronized polymers bearing azobenzene moieties in the side chain, poly (2, 5-bis {[3, 4, 5-tri (4-methoxy-4-oxyhexyloxy azobenzene) benzy oxycarbonyl} styrene), has been successfully synthesized. These polymers were characterized by 1H NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), polarized light microscopy (PLM), and one-dimensional wide-angle X-ray diffraction (1D XRD). The effects of molecular weight on liquid-crystalline behavior of these dendronized polymers were also investigated. The results show that the low molecular weight polymer P1 exhibits smecitc A (SmA)-like structure at lower temperature and nematic phase at higher temperature. Further heating P1 above the highest phase transition temperature, the sample becomes isotropic state. With the increasing of molecular weight, the high molecular weight polymer P2 exhibits more versatile intriguing liquid crystalline properties. The sequence of phase transitions of P2 follows: 2D centered rectangular columnar phase (ΦR) scaffold of main-chain and SmB-like structure of side-chain 2D centered rectangular columnar phase (ΦR) scaffold of main-chain and SmA-like structure of side-chain 2D centered rectangular (ΦR) scaffold of main-chain and isotropic side-chain 2D long-range-ordered hexagonal columnar phase (ΦH) of main-chain and isotropic side-chain. The 2D long-range-ordered hexagonal columnar phase (ΦH) of P2 still remains before the sample is completely decomposed.