Muzaffer Talu

Electrochemical copolymerization of pyrrole and aniline

Abstract This study covers the synthesis of homopolymers, copolymers and composites of aniline and pyrrole in nitrogen atmosphere using various solvent and supporting electrolytes. With the objective of examining the structure of the samples and analysing their properties, FT-IR spectra were taken, thermogravimetric analysis (TGA) was done and scanning electron microscopy (SEM) was used for microstructural analysis. The conductivity of each sample was determined through the four-probe method. Magnetic susceptibility measurements on the Gouy scale indicated that the polymers were diamagnetic. Hence, the synthesized polymers were found to contain no unpaired electrons. Homopolymerization and copolymerization reactions were carried out in an acetonitrile medium, using LiClO 4 as supporting electrolyte, in a perchloric acid medium and in a sulfuric acid medium separately, in order to analyse the effects of solvent and supporting electrolytes. As a result, the change of medium was observed to have a significant effect on the structure and properties of the resulting homopolymers. Similarly, in bilayer synthesis, changing the order of coating was observed to affect the structure and properties of samples, either partially or fully, based on the synthesis medium. For instance, coating polyaniline (PAn) over polypyrrole (PPy) in an acetonitrile + LiClO 4 medium or a water + H 2 SO 4 medium yielded composite samples, while coating PPy over PAn in the same media yielded copolymer samples. The resulting samples, however, turned out to be composites regardless of the order of coating, when the same synthesis was repeated in a HClO 4 medium.

Electrochemical copolymerization of thiophene and aniline

In this study homopolymer, copolymer, and composites of aniline and thiophene were synthesized in nitrogen atmosphere by using TEATFB (Tetraethyl ammonium tetrafluoroborate) and Lithium perchlorate as supporting electrolytes. In order to analyze their structure and characteristics, IR spectrums of the samples were taken and thermogravimetric analysis (TGA) was applied. Also, the samples were photographed under scanning electron microscope (SEM) for microstructure analysis and their electrochemical properties were observed and conductivities were obtained by four probe method. Homopolymerization and copolymerization reactions were carried out in two different solvents viz. acetonitrile and benzonitrile in order to see the solvent effect on polymerization. However, changing the solvent was found to have no significant effect on the resulting properties. It was concluded that changing the supporting electrolyte caused a structural difference in the resulting homopolymer. It also affects the properties considerably. During the bilayer preparation changing the coating turn led to variations in the properties of the samples. When polythiophene (PT) was coated with polyaniline (PA), the resulting system was a composite. However, in coating PA with PT the system was identified to be a copolymer.

Electrochemical synthesis and characterization of homopolymers of polyfuran and polythiophene and bipolymer films polyfuran/polythiophene and polythiophene/polyfuran

In this study, conductive homopolymers and bipolymers of thiophene and furan were synthesized electrochemically in an anhydrous medium in a nitrogen atmosphere using LiClO4 as the supporting electrolyte and their properties (conductivities, surface structures, thermal properties) were analyzed. Homopolymers coated onto each other in different orders were also investigated. FTIR spectra were taken to analyze structural properties. Surface analyses of polymers were clarified by scanning electron microscopy (SEM). Electrochemical properties were determined using cyclic voltammetry (CV). We found that polythiophene/polyfuran (PT/PF) and PF/PT bipolymers formed a bilayer structure. To investigate the effect of the polymerization medium on the polymer structure, the conductivities of polymers were determined by the four-probe technique and magnetic properties were analyzed via Gouy scale measurements. PF and PT homopolymers and PF/PT and PT/PF bipolymers were found to have a bipolaron nature. As a result, and as shown by thermogravimetric analysis, bipolymers have higher decomposition temperatures than the homopolymers and are thermally stable.

FTIR, Raman and NMR spectroscopic and DFT theoretical studies on poly(N-vinylimidazole).

In this study where the FTIR, Raman, (1)H NMR and (13)C NMR spectra of poly(N-vinylimidazole) which can be abbreviated as poly(NVIM) are first reported, a comparison of the experimental and theoretical vibrational spectral data of monomer NVIM and water-soluble poly(NVIM) has been given; such a comparison over the vibrational modes and associated spectral data calculated at B3LYP/6-31+G(d) level of theory for NVIM and its stable dimer forms provided significant contributions for getting a reliable interpretation of the observed vibrational spectra of poly(NVIM). The obtained results revealed that the change from NVIM to poly(NVIM) should be characterized by the disappearance of the CH₂CH bonds of the vinyl group and the appearance of the aliphatic CH and CH₂ bonds. Besides this, the thermal properties of poly(NVIM) were elucidated by thermogravimetric analyses such as TGA, DTA and DSC, while some electronic structure parameters of the most stable dimers of NVIM were investigated through the structure calculations performed by using B3LYP method and 6-31+G(d) basis set within the density functional theory (DFT) methodology.

Electrochemical Polymerization of Aniline at Low Supporting-Electrolyte Concentrations and Characterization of Obtained Films

Conductive polymers of aniline were synthesized in aqueous acidic media such as perchloric, sulfuric, hydrochloric, phosphoric, and trifluoroacetic acids and the effect of supporting electrolyte was investigated. The conductivity of each polyaniline (PAn) sample was determined by the four-probe technique. PAn (H2SO4) sample was shown to have the highest conductivity, specifically, 3.55 S cm–1. The effect of concentrations of monomers and acids on the conductivity of PAns was studied. It was observed that the conductivity decreased with increasing aniline concentration and increased with increasing sulfuric acid concentration. The conductivities of PAn (CF3COOH) were also investigated in different supporting electrolytes and highly good increments of its conductivities were obtained. Magnetic properties of the PAn salts were analyzed by Gouy balance measurements and it was found that their conducting mechanisms are of bipolaron nature. From the FTIR analysis it was found that polymerization occurs via the –NH2 group in a head-to-tail mechanism. The thermal analyses revealed that PAn (HCl) among the PAn salts studied shows the highest thermal stability. Surface analyses of polymers were clarified by scanning electron microscopy. From elemental analysis results, PAn salts were concluded to be in emeraldine structure.

Conducting Polyaniline Sensors for Some Organic and Inorganic Solvents

Abstract Polyaniline (PAn) emeraldine salts (PAn-Cl, PAn-Br, PAn-ClO4) were synthesized by the electrochemical method using different acids (HCl, HBr, HClO4). PAn salts in pellet form were used as sensors for organic (EtOH, CHCl3, C6H6) and inorganic (HCl, NH3) solvents. Electrical conductivity responses of PAns to five solvents were investigated. The change of electrical conductivity of PAns (Δσ), relative to the value measured before exposure, varied with the solvent used. The sensor properties of PAns varied depending on the nature of dopant anions such as the type and size. It was found that PAn-ClO4 has the highest sensing power on HCl, NH3, and CHCl3, and it has the lowest sensing power on C6H6.

Graft Copolymerization of Methyl Methacrylate onto Poly(Ethylene Terephthalate) Fibers Using Benzoyl Peroxide

Abstract The graft copolymerization of methyl methacrylate onto poly(ethylene terephthalate) fibers has been studied using benzoyl peroxide as initiator. The grafting reactions were carried out within the 70 to 90°C temperature range, and the variations of graft yield with monomer and initiator concentrations were also investigated. The overall activation energy for grafting was calculated as 34.1 kcal/mol. The results of dyeability with the disperse dye suggested that diffusion into the fiber structure was moderately difficult when the graft yield reached 14−15%. The maximum graft yield was obtained at a benzoyl peroxide concentration of 4.00 × 10−3 M. The decomposition temperature values obtained from thermogravimetric analysis show that the thermal stability of poly(ethylene terephthalate) fibers decreased as a result of grafting. Further, such change in the properties of methyl methacrylate grafted fibers as density, diameter, and moisture regain were also determined.

Alkaline hydrolysis of poly(ethyl acrylate) and styrene-ethyl acrylate copolymer

Abstract This article deals with the alkaline hydrolysis of poly(ethyl acrylate) and of the copolymer of ethyl acrylate (68.4%) and styrene (31.6%). Chemical changes during hydrolysis were evaluated by means of flame photometry and i.r. spectroscopy. The influences of temperature, concentration of hydrolytic reagent and reaction time upon the rate of hydrolysis were studied. With a 10-fold excess of KOH, first-order hydrolysis rate constants were obtained; a plot of the conversion of ester groups vs time is typical. The degree of hydrolysis depended on solvent, decreasing in the order acetone > THF > diethyl ether > benzene.

The Modification of Butadiene-Acrylonitrile Rubber with Vinylcyclohexyl Ketone

Abstract Butadiene-acrylonitrile-vinylcyclohexyl ketone (BD-AN-VCHK) terpolymer was synthesized by radical polymerization. The structure of the synthesized terpolymer was elucidated by IR spectroscopy and physical and mechanical tests. BD-AN-VCHK terpolymer was stable at lower temperatures and exhibited good adhesive properties. It was also observed that the yield of terpolymer was dependent upon the initial concentration of VCHK and pH of the media. The percentage of conversion increased by increasing the initial concentration of VCHK. With addition of 10.8% VCHK to the BD-AN mixture, the glass transition temperature (Tg) value of the polymers decreased from −40 °C to −57 °C. However further increase of VCHK ratio (20.4%) resulted in the formation of the polymers with Tg value of −48 °C. It was shown that this was due to the fact that VCHK, entering the structure during polymerization process, converted the trans structure of butadiene sequences into the cis form.