Synthesis and properties of polyamides and polyesters on the basis of 2,2′-bipyridine-5,5′-dicarboxylic acid and the corresponding polymer-ruthenium complexes

Abstract

Two series of polyamides and polyesters derived from 2,2′-bipyridine-5,5′-dicarboxylic acid have been synthesized. Different types of aliphatic and aromatic diamine and diol monomers with different structure were polymerized with the diacid or diacid chloride by using different polymerization methods. Most of these polymers exhibited modest thermal stabilities with decomposition temperatures in the range 320-500 °C, depending on the structure of the polymer main chain. It was found that some polyamides with a rigid main chain formed a lyotropic mesophase when dissolved in concentrated sulfuric acid or HMPA-4% LiCl solvent systems. For those polyamides and polyesters with a more flexible main chain, a thermotropic liquid crystal phase was observed. If a long and flexible pendant chain was attached to the polyesters, side chain melting was observed before the onset of the crystalline-nematic transition. The 2,2′-bipyridyl moieties were able to form a complex with ruthenium. These polymer-ruthenium complexes were either synthesized by metalation of the polymers or synthesized directly from the corresponding ruthenium-containing monomer. After the formation of ruthenium complexes, they were able to enhance the photosensitivity and charge carrier mobility of the polymers. The ruthenium-containing polymers also emit red light at ca. 700 nm owing to the emission from the metal-ligand charge-transfer excited states. Some polymers with good film forming properties were fabricated into simple single-layer light-emitting devices, and red light emission was observed when the devices were subjected to forward bias.