H. Ibrahim Unal

Synthesis and characterization of poly(dihalophenylene oxides) by thermal decomposition of copper complexes with tetramethylethylenediamine and ethylenediamine ligands

Abstract Thermal polymerization of bis(trihalophenoxo)- N,N,N′,N′ -tetramethylethylenediamine copper( ii ) and bis(trihalophenoxo)ethylenediamine copper( ii ) was achieved in toluene at 70°C. The dependences of intrinsic viscosity and the percentage yield of the polymers on a sequence of increasing decomposition times of copper complexes were investigated. Structural analyses of the polymers were carried out using mainly 1 H nuclear magnetic resonance spectroscopy and differential scanning calorimetry. 1,4-Catenation was highly favoured over 1,2-addition in 4-bromo-2,6-dichlorophenoxide- and 2,4,6-triiodophenoxide- (with ethylenediamine ligand) and 2,4,6-triiodophenoxide- (with tetramethylethylenediamine ligand) derived polymers. However, polymers synthesized from 2,4,6-trichlorophenoxide with either ligand displayed a selectivity in favour of 1,2-catenation, whereas for 2,4,6-tribromophenoxide with ethylene diamine ligand, 1,4-catenation and ortho substitution took place at roughly equal rates.

Conducting Composites and Blends of Polythiophene and Polyoxymethylene

Abstract Conductive polyoxymethylene/polythiophene (POM/PT) composites and PT/POM blends were prepared by in situ chemical polymerization using FeCl3 oxidant and mixing in solutions, respectively. It was found that the properties of the composites and blends were different from those of homopolymers and also from each other. Formation of polymer and composites was supported by FT-IR analyses. According to the results of thermal analyses (TGA), it was shown that polymers and composites have good thermal stability. The thermal degradation temperature of POM/PT composite containing 88% PT is higher than those of the other composites. The thermal degradation temperature of PT/POM blend containing 27% POM was described as higher than that of the other blends. The morphological structures of polymers and composites were studied by scanning electron microscopy (SEM). It was found that morphological structures of composites were smoother than that of PT. The crystal structures of polymers and composites were investigated by X-ray diffraction analysis. It was found that the crystal regions increased with increasing amount of POM in the composites and blends.

Enhanced electrokinetic properties and antimicrobial activities of biodegradable chitosan/organo-bentonite composites

In this study, chitosan (CS), Na+-bentonite (Na+-BNT) and chitosan/organo-bentonite (CS/O-BNT) biodegradable composites having three different compositions were investigated. Electrokinetic measurements were examined in aqueous medium by taking the effects pH, electrolytes (NaCl and BaCl2), surfactants (CTAB and SDS), and temperature into account. It was noticed that the initial ζ-potential of Na+-BNT shifted from negative (ζ=-35mV) to positive region (ζ=+13mV) with increasing polycationic CS content in the composite structure as aimed. Divalent 2:1 electrolyte (BaCl2) caused to shift the ζ-potentials of all the dispersions to more positive regions. While the most negative effect on ζ-potential of the composites was reached with SDS, which reduced the value of ζ-potential to -39mV for CS(1)/O-BNT composite, the most positive effect was monitored with CTAB (ζ=+40mV) for CS(3)/O-BNT composite. Further, the composites were tested against various bacterial (Gram-positive and Gram-negative) and fungal microorganisms at various concentrations and results obtained were compared with the reference antibiotics and fungicide. According to inhibition zone values accomplished, antibacterial and antifungal activities of the CS/O-BNT composites are increased with increasing CS content as proportional with their positive ζ-potential values.

Electrorheological properties of polyaniline/K-feldspar conducting composite

In this study, synthesis of conducting polyaniline (PAn)/potassium-feldspar (K-feldspar) composites, having various amounts of PAn, was carried out using (NH4)2S2O8 as oxidizing agent. The conducting composites were characterized by a series of techniques namely: Fourier transform–infrared, X-ray diffraction, scanning electron microscopy, thermogravimetry analysis, two-probe conductivity, magnetic susceptibility, and particle size measurements. For electrorheological (ER) measurements, the conductivities of the composites were reduced by a dedoping process. A series of suspensions were prepared in silicone oil, having various volume fractions, and then subjected to colloidal stability, flow rate, ER and creep-recovery tests. Enhancement in the electric field-induced viscosities and shear thinning non-Newtonian viscoelastic behavior was observed for all the composite materials studied. Recoverable viscoelastic deformations were detected from the creep and creep-recovery tests under externally applied electric field thus; they were classified as smart materials.

Electrorheology and creep-recovery behavior of conducting polythiophene/poly(oxymethylene)-blend suspensions

Electrorheological properties and creep-recovery behavior of polythiophene/polyoxymethylene-blend having PT(50%)/POM(50%) composition were investigated. Particle size, conductivity and dielectric values were measured to be 24.77 μm, 3.85 × 10−5 S·m−1 and 26.75, respectively. Sedimentation ratio was measured to be 64% at the end of 16 days. The effects of dispersed particle volume fraction, external electric field strength, shear rate, frequency and temperature on ER properties and storage modulus of PT/POM-blend/silicone oil (SO) suspensions were examined. Enhancement were observed in the electric field viscosities of the suspensions and thus they were classified as a smart material. Shear thinning non-Newtonian viscoelastic behavior was determined for PT/POM-blend/SO system. Further, time-dependent deformation was examined by creep-recovery tests and recoverable viscoelastic deformation established.