Molecular Design, Syntheses And Secondary Polymerization Of Functional Groups Modified O-dihydroxybenzene

Conducting polymers (CPs), such as polyacetylene, polythiophene, polypyrrole, etc., have attracted great attention due to their wide fundamental interest and potential industrial application. Unlike poly(p-phenylene) and polyaniline, which generally are para-polymerized, poly(o-phenylene) motif consists of multiple phenylene units that are linked together at their ortho positions. Nowadays many studies have focused on the polymerization of o-phenylenes because of their special structures, especially two articles in Nature Chemistry in2011. In addition, CPs with various properties can be achieved via adjusting the electronic character of the π-orbit along the neutral polymer backbone, including main chain and pendant group structural modification. Therefore, design and synthesis of new conjugated polymer with special functional substituents are highly desirable. In this paper, novel conducting polymers based on functional groups modified o-dihydroxybenzene were synthesized by sencondary polymerization. The synthesis conditions, structures and properties of as-formed polymers were studied in detail.1. Precursor monomer BCHB that contained two pendent electro-active units was designed and successfully synthesized, and PBCHB films were electrosynthesized by direct anodic oxidation of BCHB at different potentials in CH2Cl2-BFEE (3:7, by volume) with good redox activity and stability. UV-vis, FT-IR,1H NMR spectral analyses, and MALDI-TOF MS results determined that the electrochemical polymerization of BCHB at lower applied potentials (e.g.0.5and0.7V) preferentially occurred on catechol units and the polymers were soluble in common organic solvents. When the applied potential increased to1.0V, the polymerization would occur both on catechol and carbazole units resulting in the formation of network polymer films, which were insoluble in any common organic solvents. With these results, it can be obtained that the PBCHB films could be synthesized electrochemically on different polymerized units by controlling the applied potentials. Furthermore, PBCHB showed stronger blue emissions at much longer wavelengths than their monomers due to the formation of conjugated polymers.2. A novel acrylate functionalized monomer o-phenylene diacrylate (o-PDA) was designed and synthesized. Through radical copolymerization of o-PDA with acrylic acid (AA), a precursor polymer, oligo(o-PDA-co-AA)(O1) was obtained. Cross-linked P1film was successfully achieved by electrochemical copolymerization of monomer mixtures of o-DHB and O1. UV-Vis, FT-IR, and1H NMR spectra were used to characterize the structures of the copolymer. Since AA and o-DHB were introduced into the polymerization processes successively, as-obtained copolymer showed good electrochemical activity and stability. According to the fluorescence spectra, the copolymers show strong emission peaks at415nm, indicating good blue-light emmitting properties of copolymers and that the introduction of polyacrylate structures into the copolymers have little effect on their fluorescence properties. TG analysis suggests that as-formed copolymers exhibit good thermal stability.3. Precursor monomer2-methoxyphenyl acrylate (2-MOPA) was designed and synthesized. Through radical copolymerization of2-MOPA with acrylic acid (AA), a precursor polymer, oligo(2-MOPA-co-AA)(O2) was obtained. Cross-linked P2film was successfully achieved by electrochemical copolymerization of monomer mixtures of HMOB and O2, respectively. UV-vis, FTIR, and1H NMR spectra were used to characterize the structures of the copolymers. Since AA and HMOB were introduced into the polymerization processes successively, as-obtained copolymer showed good electrochemical activity and stability. Copolymer showed a strong emission peaks at487nm, indicating the good blue-light emmitting properties of copolymer and that the introduction of polyacrylate structures into the copolymers has little effect on their fluorescence properties. TG analysis suggests that as-formed copolymers exhibit good thermal stability.4. The ethylene oxide (EO) functionalized monomer1-(2,3-epoxypropyl)-2-methoxybenzene (EPMOB) was synthesized. The precursor polymer oligo(1-(2,3-epoxypropyl)-2-methoxybenzene)(OEPMOB) was prepared using anionic ring-opening polymerization method. Conjugated network films of homopolymers POEPMOB, PHMOB, and copolymers with various feed HMOB ratios were obtained via secondary electropolymerization using cyclic voltammetry in the binary solvent system containing CH2Cl2and BFEE (3:7, by volume). The properties of the as-formed poly(OEPMOB-co-HMOB) films depended on the mixture feed ratios and the applied potential. When the feed ratio of HMOB units into the copolymer chain reached to1:1, the thermal stability of P3film was improved obviously in comparison with that of POEPMOB and PHMOB. The pendant electroactive HMOB units were converted to PHMOB and were proven by FT-IR. The copolymers dissolved in DMSO were good blue-light emitters, with a maximum emission at about392nm in doped state. Based on the above experiments and comparisons, the introductions of EO and HMOB units into the skeletal copolymer backbone have positive effect on their thermal stabilities, and negative effect on their fluorescence properties.