title: Spectroscopic characterization of polyaniline formed by using copper(II) in homogeneous and MCM-41 molecular sieve media.
abstract: This work emphasizes the important role of the synthetic parameters in the structure of the polymeric material obtained in the aniline polymerization. The polymers formed by the oxidative polymerization of aniline by copper(II) ions in acidic aqueous solution, acetonitrile/water medium, and also copper(II) acetate complex encapsulated into MCM-41 molecular sieve were characterized by resonance Raman spectroscopy using three exciting laser lines and other techniques such as UV-vis, FTIR, and XANES (Nitrogen K edge). Additionally the products were investigated by thermogravimetric analysis and powder X-ray diffraction. When Cu(II) ions in acidic aqueous medium are used, emeraldine salt (ES-PANI) is formed through the usual head-to-tail polymerization mechanism, while in acetonitrile/water medium a polymer is observed having mainly phenazine-like rings, quinonediimine, and/or phenylenediamine segments in the chains, suggesting that a distinct mechanism is operating. The average molecular weights of the free polymers synthesized in water and in acetronile/water were, respectively, ca. 37 300 and 16 900 Da. The encapsulated polymer synthesized in Cu(II)-MCM-41 is a polymeric mixture of (i) ES-PANI and (ii) the polymer obtained when this metal cation was used as oxidant in acetonitrile/water medium. All the characterization data were compared to those ones obtained for standard free polyaniline and also for the encapsulated polymer into mesoporous MCM-41 formed by using persulfate in acidic aqueous medium as oxidant.
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05513-970, São Paulo, SP, Brazil.
authors.forename: Celly M S
authors.initials: CM
authors.lastname: Izumi
authors.forename: Vera R L
authors.initials: VR
authors.lastname: Constantino
authors.forename: Marcia L A
authors.initials: ML
authors.lastname: Temperini
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D000814:Aniline Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission / Q000295:instrumentation / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000295:instrumentation / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation / Q000379:methods; D013059:Spectrum Analysis, Raman / Q000295:instrumentation / Q000379:methods; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D000097:Acetonitriles; D000814:Aniline Compounds; C509968:MCM-41; D009942:Organometallic Compounds; D012996:Solutions; C416807:polyaniline; D014867:Water; C015092:cupric acetate; D012822:Silicon Dioxide; C032159:acetonitrile