Serap Kavlak

Effect of some selective aromatic cosolutes on the main thermodynamic parameters of aqueous poly(n-vinyl-2-pyrrolidone) solutions

Cloud-point curves and theta temperatures have been determined for aqueous solutions of poly(N-vinyl-2-pyrrolidone) at several concentrations for a variety of aromatic additives (benzoic acid, o- and p-hydroxy benzoic acid, aniline, o- and p-hydroxy aniline). The theta temperature of polymer is suppressed at lower temperatures depending on the chemical structure and the concentration of additives. The effectiveness, in decreasing order, of the cosolutes in reducing the temperature is: p-hydroxy benzoic acid > o-hydroxy benzoic acid > p-hydroxy aniline > o-hydroxy aniline benzoic acid > aniline. It is understood that changes in theta temperatures caused by the cosolute result from the changes taking place in the hydrophilic and hydrophobic interactions among polymer, solvent and polymer-solvent interactions from the added cosolute.

Preparation, characterization and dynamical mechanical properties of dextran-coated iron oxide nanoparticles (DIONPs)

Abstract Dextran-coated iron oxide nanoparticles (DIONPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging (MRI) contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. This paper reports the experimental detail for preparation, characterization and investigation of thermal and dynamical mechanical characteristics of the dextran-coated Fe3O4 magnetic nanoparticles. In our work, DIONPs were prepared in a 1:2 ratio of Fe(II) and Fe(III) salt in the HCl solution with NaOH at given temperature. The obtained dextran-coated iron-oxide nanoparticles structure–property correlation was characterized by spectroscopic methods; attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and XRD. Coating dextran on the iron-oxide proof of important peaks can be seen from the ATR-FTIR. Dramatic crystallinity increment can be observed from the XRD pattern of the iron-oxide dextran nanoparticles. The thermal analysis was examined by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). Dynamical mechanical properties of dextran nanoparticles were analysed by dynamic mechanical analysis (DMA). Thermal stability of the iron oxide dextran nanoparticles is higher than that of the dextran.

Experimental Approaches to Investigation of the Interaction in between Anhydride Containing Copolymer and Poly (N-vinyl-Pyrrolidone) Blends

Blending or complexation of a polymer with another polymer has great practical interest, since this modification gives the chance to modify physical properties, functionality of polymer without synthetic reactions. In the present study, poly(maleic anhydride-alt-acrylic acid) [poly(MA-alt-AA)] was prepared by the binary copolymerization of the corresponding monomers by charge-transfer complex (CTC) copolymerization. Water-soluble functional copolymers poly(MA-alt-AA) and poly(N-vinyl-2-pyrrolidone) (PVP) polymer blends were prepared by casting from water at room temperature, and their compatibility properties were investigated in the solid state. The high compatibility of poly(MA-alt-AA) and PVP can be explained by specific interactions between the carboxylic acid groups of the copolymer and the carbonyl groups of the PVP. Changes of the special features of the pure components and their various compositions in the blends were investigated by ATR-FTIR, HR-Raman and 1H-,13C-NMR spectroscopic techniques and dynamic mechanical analysis (DMA).