Ayhan Oral

Synthesis and Characterization of Poly(L-Lactic acid)/Clay Nanocomposite via Metal-Free Process

Biopolymer nanocomposite was synthesized using metal-free catalyst which is Montmorillonite-K10 as organic filler and acid catalyst for polymerization of L-Lactic acid. To evaluate the effect of Montmorillonite onto polymer properties, 1, 3 and 5% clay were used. Products were characterized using X-ray diffraction and transmission electron microscopy. Thermal parameters of products were investigated via differential scanning calorimeter and thermo-gravimetric analyzer. Thermal stability, degree of crystallinity, temperatures for glass transition, crystallization and melting of the nanocomposites were studied. Effect of clay onto molecular weight was investigated via gel permeation chromatography. It was found that properties of polymer were influenced by addition of clay.

Synthesis of poly-2-hydroxyethyl methacrylate-montmorillonite nanocomposite via in situ atom transfer radical polymerization

The poly-2-hyroxyethyl methacrylate (PHEMA)/clay nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. To produce organically modified montmorillonite (MMT) that has ATRP initiator moiety, a new catalyst that consists of quaternary ammonium salt moiety and an initiator moiety was synthesized. This initiator was intercalated into the interlayer spacing of the MMT. The polymerization reaction was carried out in a mixed solvent system consisting of methyl ethyl ketone and 1-propanol at 50 °C, using the initiator that has been already synthesized with a copper bromide catalyst. The 2, 2′-bipyridyl (bpy) complex was used as ligand. The products were characterized via Fourier transform infrared, nuclear magnetic resonance ( 1 H NMR, 12 C NMR), transmission electron microscopy, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry.

Structural changes in Poly(lactic acid)–zeolite nanocomposites exposed to 60Co gamma rays

ABSTRACT Poly(lactic acid) (PLA) nanocomposites containing 3%, 5% and 7% zeolite used in the present research study were prepared by solution casting. The PLA nanocomposites were structurally characterized by Scanning Electron Microscopy and Fourier-transform infrared spectroscopy. The effects of the gamma radiation at the absorbed doses of 10, 15 and 20 kGy on the structures and thermal properties of the nanocomposites were investigated in a tetrahydrofuran solvent. Thermodecomposition tests and analyses were carried within 30–500°C range at the rate of 10°C min−1 by thermogravimetric analysis (TG). The activation energies for thermal degradation of the nanocomposites were calculated from their TG data by Flynn–Wall–Ozawa method. The G values of the nanocomposites were calculated based on molecular weights which were measured by means of gel permeation chromatography before and after the gamma irradiation. The Ea and molecular weight results showed that addition of zeolite to the PLA affected the radiation resistance of the polymer.

Grafting of poly(ε-caprolactone) on electrospun gelatin nanofiber through surface-initiated ring-opening polymerization

ABSTRACT Gelatin–polycaprolactone hybrid materials are being used in medicinal applications such as drug delivery, tissue engineering applications nowadays. In this study, gelatin–polycaprolactone graft copolymer was synthesized through ring-opening polymerization process instead of conventional grafting methods using potentially cytotoxic crosslinkers, or applying plasma, aminolysis reactions. Gelatin nanofiber (GNF) was produced by electrospinning process before immobilization of poly(ε-caprolactone). Ring-opening polymerization of ε-caprolactone was successfully initiated on the surface of GNF using tin(IV) isopropoxide and gelatin (primary amine functional groups) as an initiator and a coinitiator, respectively. The growing of polymer chains on GNF was indicated by both scanning electron microscope and energy-dispersive X-ray spectroscopy. Chemical structure was characterized through infrared spectrum, thermal behaviors and the material composition was analyzed with thermogravimetric analysis, wettability and hydrophilicity were determined by water contact angle measurements. GRAPHICAL ABSTRACT

Preperation of Poly (Lactic Acid) Nanocomposite via Catalyst Modified Montmorillonite

Biopolymer nanocomposite of polylactic acid was synthesized from lactic acid using tin ions exchanged Cloisite Ca++. The tin molecules between the Cloisite Ca++ layers catalyzed the lactic acid polymerization and also this clay played a role as a nanofiller. Presence of tin molecules increased the molecular weight of the polymer compared with the polymer that was synthesized with the presence of just Cloisite Ca++. Both exfoliated and intercalated nanocomposite structures were observed as the results of X-ray diffraction analysis and transmission electron microscopy images. Also, changes of polymers thermal degradation and other thermal properties such as glass transition temperature, melting temperatures were investigated via thermogravimetric analysis and differential scanning calorimetry. GRAPHICAL ABSTRACT