H. Yuksel Guney

In situ polymerization synthesis and characterization of single wall nanotubes/ poly(vinyl)triazole nanocomposites

The synthesis of single wall nanotubes (SWNT)/poly(vinyl)triazole (PVTri) composites by in situ emulsion polymerization method and its chemical and physical properties were investigated throughout this work. The surface modification of the SWNT by nitric acid treatment and air oxidation has improved the dispersion of the SWNT in the PVTri matrix. The SWNT/PVTri composite is obtained by covalent bonding of the carboxyl terminated SWNTs to PVTri. The effect of covalent bond formation between PVTri and SWNT on the thermal and electrical properties of the composite is also studied. The spectroscopic, thermal, and microscopic analysis has confirmed the structure, homogeneity, and the morphology of surface functionalized SWNT and SWNT/PVTri composites. SWNT/PVTri composites showed enhanced chemical stability in many common solvents and high electrical conductivity.

Synthesis of new 2,5-di(thiophen-2-yl)furan-3-carbonitrile derivatives and investigation of the electrochromic properties of homopolymers and co-polymers with EDOT

New 2,5-di(thiophen-2-yl)furan-3-carbonitriles as thiophene–furan–thiophene type monomers (2a and 2b) were synthesized by the oxidation of 2,5-di(thiophen-2-yl)-4,5-dihydrofuran-3-carbonitriles which were prepared by the reaction of 3-oxopropanenitriles with alkenes mediated with manganese(III) acetate using DDQ (2,3-dichloro-5,6-dicyano-p-benzoquinone). The monomers and their copolymers with EDOT were electrochemically polymerized in acetonitrile (AN)/LiClO4. The electrochemical, spectroelectrochemical and morphological properties of the resulting polymer and copolymer films were investigated by cyclic voltammetry, UV-visible spectroscopy and atomic force microscopy. Observed differences in cyclic voltammetry, UV-vis spectroscopy and neutral state absorption (π–π* transition) have been accepted as evidence for the copolymerization. Copolymer films have distinct electrochromic properties according to superposition of the contained polymer properties. In addition the dissolution problem thats causing the instability of poly2b has been fixed with copolymerization. Switch time measurements showed that copolymer films are candidates for ECD applications due to their stability, fast response time and good optical contrast.

Effect of LiClO4 Salt on Dielectric Properties of Acrylonitrile-Methyl Methacrylate and Acrylonitrile-Isobutyl Methacrylate Copolymers

Poly(acrylonitrile-co-isobutyl methacrylate), PAN-co-PIBMA, and poly(acrylonitrile-co-methyl methacrylate), PAN-co-MMA copolymers are synthesized by emulsion polymerization. The structural characterization is done by FTIR and 1H-NMR spectroscopy and thermal analyses are performed by thermogravimetric analysis (TGA). After various amounts of LiClO4 salt loading into copolymer films, the dielectric properties of these films at different temperatures and frequencies are determined. The effects of different methacrylate groups and salt content on the dielectric properties of copolymers are investigated. It is found that the dielectric constant increases systematically with increasing MMA and IBMA content in the copolymer. The samples with higher salt content show higher ac-conductivities.

Non‐reproducible Electrical Properties Of Semiconductor PVDF‐HFP (Hexafluoropropylenevinylidenefluoride) Copolymer

The I‐V characteristic of carbon black‐filled PVDF‐HFP copolymer has been investigated as functions of electrical field, temperature and time. In addition, the conductivity has been measured by applying fixed voltage at different temperature. Electrical properties of the carbon‐black‐filled PVDf‐HFP have been compared with the electrical properties of pure PVDF and PVDF‐HFP samples. The variation of conductivity with respect to electrical field and temperature has been obtained experimentally. Although the conductivity has been especially increasing with using temperature as semiconductor, it tends to decrease after a certain electrical field. Because of the dipolar structure, the I‐V characteristic of the material has shown non‐reproducible and hysteresis behavior. It has observed that the variation of conductivity as a function of temperature under fixed electrical field followed different exponential ways which depends on time after a certain temperature value.