Taner Tanrisever

Kinetics of Emulsifier-Free Emulsion Polymerization of Methyl Methacrylate

The influences of polymerization temperature, initiator and monomer concentrations, ionic strength of the aqueous phase, as well as ethylene glycol dimethacrylate (EGDM) co-monomer, on the kinetics of the emulsifier-free emulsion polymerization of methyl methacrylate (MMA) and on the properties of the resulting poly(methyl methacrylate) (PMMA) lattices were studied. The polymerizations were carried out using potassium persulfate (KPS) as the initiator. Monodisperse PMMA lattices with particle diameters varying between 0.14–0.37 μm and polymer molecular weights of the order 0.4 × 106 to 1.2 × 106 g/mol were prepared. The initial rate of polymerization increases with increasing temperature, KPS-MMA mole ratio, EGDM content, or with decreasing ionic strength of the aqueous phase. It was shown that the bead size can be limited by reducing the monomer concentration or by using the cross-linking agent EGDM. The ionic strength of the aqueous phase has a dominant effect on final particle diameter and polymer molecular weight. The uniformity of the latex particles increases as the temperature increases or as the initiator concentration decreases. The experimental results can be reasonably interpreted by the homogeneous nucleation mechanism of the emulsifier-free emulsion polymerization of MMA.

A Simple Way to Synthesize Superparamagnetic Iron Oxide Nanoparticles in Air Atmosphere: Iron Ion Concentration Effect

We have synthesized iron oxide nanoparticles in air atmosphere by coprecipitation. The ratio of was fixed at 2/3. The total amount of iron ions in the solution was varied from 250 mmol to 12.5 mmol. X-ray diffraction (XRD) patterns showed the characteristic peaks of iron oxide phases. We observed that the crystallinity reduced and particle sizes calculated from XRD patterns decreased as the iron ion concentration in the solution decreased. Fourier transform infrared spectroscopy analysis exhibited the Fe-O vibration band at 560-580 confirming the iron oxide formation. The mean physical sizes obtained from a transmission electron microscope are around 8 nm. According to the magnetic measurements, all samples are superparamagnetic at room temperature showing an increase in saturation magnetization up to 63.71 emu/g. Magnetic sizes of the particles vary from 7.45 nm to 4.88 nm with the change of iron ion concentration.

Poly(methyl methacrylate) films for organic vapour sensing

Optical constants and fabrication parameters are investigated using surface plasmon resonance (SPR) studies on spun films of poly(methyl methacrylate) (PMMA) derivatives in contact with two different dielectric media. A value of 1.503 for the refractive index of PMMA films produced from a solution having concentration of 1?mg?ml?1 at the speed of 3000?rpm is in close agreement with the data obtained from ellipsometric measurements. The film thickness shows a power-law dependence on the spin speed but the thickness increases almost linearly with the concentration of the spreading solution. These results are in good agreement with the hydrodynamic theory for a low-viscosity and highly volatile liquid. On the basis of SPR measurements under dynamic conditions, room temperature response of PMMA films to benzene vapours is found to be fast, highly sensitive and reversible. The sensitivity of detection of toluene, ethyl benzene and m-xylene is much smaller than that of benzene.

Spun thin films of poly(methyl methacrylate) polymer for benzene sensing

Thin films of poly(methyl methacrylate) (PMMA) were deposited on suitably prepared substrates by spinning the spreading solution in chloroform at 3000?rpm for atomic force microscopy and surface plasmon resonance studies. Four different types of PMMA were used within a range of molecular weight between 540 and 760?kg?mol?1. The film surface was found to be uniform. Values of refractive index for PMMA film were found to exist in the range of 1.50 ? 0.04 to 1.53 ? 0.02. All films exhibited fast response to the exposure of benzene vapour but the sensitivity of detection depended upon the molecular weight.

Parametric characterizations in superparamagnetic latex

The effect of synthesis parameters on the production of superparamagnetic latex, which are magnetite nanoparticles covered with a poly(methyl methacrylate) layer, were studied. The synthesis method was based on the developed route of emulsifier-free emulsion polymerization. Under this study, effects of the monomer and initiator concentrations, the amount of magnetic sol, the stirring rate and the adding rate of the magnetic sol on the properties of synthesized latexes were investigated. The characterizations were performed by a high resolution transmission electron microscopy, a dynamic light scattering, a vibrating sample magnetometer and a gel permeation chromatography. The results showed that the monomer concentration was found to be the most effective parameter on latex stability. As the initiator amount and the stirring rate increased, saturation magnetization and average molecular weight decreased due to the reactions occurring between surfaces of magnetite nanoparticles and initiator fragments. On increasing amount of magnetic sol, the saturation magnetization and polymer molecular weight increased but the size of nanospheres was unchanged because of the ions in magnetic sol. It was seen that the desired size and magnetic properties of the latex could be obtained since the parameters were found to have substantial impact on their properties.