Günay Kibarer

Reaction kinetics for laccase-catalyzed polymerization of 1-naphthol.

Laccase-catalyzed oxidative polymerization of 1-naphthol was carried out in a closed system containing acetone and sodium acetate buffer. The effects of initial 1-naphthol and dissolved oxygen concentrations on the initial reaction rate were investigated. A multiplicative mathematical model, using a function of 1-naphthol and dissolved oxygen concentrations, was developed for enzymatic polymerization and the corresponding biokinetic parameters have been evaluated for the first time. The activation energy and reaction rate constant of the laccase-catalyzed 1-naphthol polymerization were calculated as 57 kJ/mol and 311 l/s, respectively. The activation energy calculated was in the typical range of 30-60 kJ/mol and rate constant was of the order of magnitude of previously reported values for laccase-catalyzed reactions with different monomers.

Effects of reaction conditions on laccase-catalyzed α-naphthol polymerization

Enzymatic oxidative polymerization of α-naphthol was carried out batch-wise with the laccase enzyme, produced by Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone (solvent) and sodium acetate buffer for pH control. The effects of the organic solvent (acetone) composition, monomer (α-naphthol) and enzyme concentrations, buffer pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen. The optimum acetone composition, pH, monomer, dissolved oxygen and enzyme concentrations were determined as 50% (v/v), 5, 3409 gm−3, 20.3 gm−3 and 0.173 U cm−3, respectively; these values provided the most desirable conditions for initial reaction rate. Temperature rise supported the rate increase up to 37 °C, after which the rate tended to be stable due to a drop in dissolved oxygen concentration. The product polymer, poly(α-naphthol), with an average molecular weight of 4920 Da was soluble in common organic solvents. © 2000 Society of Chemical Industry

The important role of thermodynamic interaction parameter in the determination of theta temperature, dextran/water system

Abstract The interaction parameter χ was evaluated through the sum of the individual values of enthalpy and entropy dilution parameters, χ H and χ S , for different molecular weights of dextran samples. Subsequently, ((1/2)− χ ) versus temperature relation yielded the theta temperature interpolated to 316.5±0.3 K. Similarly, the dependence of second virial coefficient, A 2 , on temperature was also studied from which another theta temperature was determined equal to 317.0±0.5 K. These two individual theta temperatures evaluated via interpolation methods employing interaction parameter and second virial coefficient were quite in accordance with that calculated as 317.2±0.6 K from intrinsic viscosity measurements achieved between the temperature intervals of 25°C and 43°C for the same system, previously.

Complex-radical terpolymerization of acceptor–donor–acceptor systems: Maleic anhydride (n-butyl methacrylate)–styrene–acrylonitrile

Some features of radical ternary copolymerization of maleic anhydride (MA)–styrene (St)–acrylonitrile (AN) and n-butyl methacrylate (BMA)–St–AN acceptor–donor–acceptor monomer systems have been revealed. The terpolymer compositions and kinetics of copolymerizations were studied in the initial and high conversion stages. The considerable divergence in the copolymer compositions was observed when a strong acceptor MA monomer was substituted with BMA having comparatively low acceptor character in the ternary system studied. Obtained results show that terpolymerization proceeded mainly through “complex” mechanism in the state of near binary copolymerization of St…MA (or BMA) and AN…St complexes only in the chosen ratios of complexed monomers. The terpolymers synthesized have high thermal stabilities (295–325 °C), which is explained by possible intermolecular fragmentation of AN-units through cyclization and crosslinking reactions during thermotreatment in the isothermal heating conditions.

Preparation and properties of invertase immobilized on a poly(maleic anhydride-hexen-1) membrane.

Poly(maleic anhydride-alt-hexen-1)(poly(MA-alt-H-1)) has been synthesized by radical polymerization and characterized by DSC, FT-IR, acid number determination, viscometric and NMR methods. Data showed that the co-polymer is an alternating co-polymer whose composition does not depend on the monomer feed composition. Invertase was immobilized onto a poly(MA-alt-H-1) membrane via glutaraldehyde and bovine serum albumin. The K m value of poly(MA-alt-H-1)-invertase was approximately 4.4-fold higher than the free enzyme, indicating decreased affinity by the invertase for its substrate (sucrose), whereas V max was lower for the immobilized invertase. Immobilization improved the pH stability of the enzyme, as well as its temperature stability. Immobilized samples obtained were stable and could be used many times over a period of 2 months without considerable activity loss.

Multifunctional PP-Based Nanocomposites Incorporated with Organoclays, Poly(MA-alt-1-Dodecene)-g-SiO2 Nanoparticles and Bioengineering Polyesters in Melt by Reactive Extrusion

ABSTRACT Polypropylene-based multifunctional nanocomposites were fabricated in melt by a one-step reactive extrusion using a twin-screw extruder. The in situ chemical and physical processes during the extrusion of polymer blend composites consisting (1) polypropylene as a matrix polymer, (2) polypropylene–g-maleic anhydride graft copolymer compatibilizer, (3) copolymer–g-SiO2 encapsulated nanoparticles, (4) biodegradable polyesters, and (5) reactive and nonreactive organoclay nanofillers were investigated. The crystallinity, thermal stability, rheological, mechanical parameters, and surface and internal morphologies of the nanocomposites have been improved compared to polypropylene and its composites. Moreover, the colloidal copolymer–silica nanoparticles play an important role in the formation of nanocomposites with well dispersion in morphology. GRAPHICAL ABSTRACT

EPDM Elastomer and Biothermoplastic Polyester-based Silicate-layered Multifunctional Nanocomposites Incorporated with Poly(MA-alt-α-olefin)-g-APTS-SiO2 NPs and PP-g-MA by Reactive Extrusion Nanotechnology

ABSTRACT Multifunctional polymer blend nanocomposites consisting EPDM elastomer as a matrix polymer, bioengineering polyesters (PLA and PCL), PP-g-MA compatibilizer and covalently encapsulated colloidal alternating reactive copolymer-g-γ-aminopropyl trimethoxysilane-silica nanoparticles as reactive compatibilizer nanofillers, and organoclay (reactive ODA-MMT and complexable DMDA-MMT) nanofillers were fabricated in melt by a one-step reactive extrusion nanotechnology. The effects of bioengineering polyesters and their molecular mass, origin of organology, and reactive PP-g-MA compatibilizer were evaluated. Unique nanostructures, lower particle sizes and crystallinity, SEM–TEM morphologies, higher thermal behaviors, good mechanical and rheological properties of thermoplastic multifunctional nanocomposites were evaluated. GRAPHICAL ABSTRACT

Preparation of Poly(MA-alt-α-olefin-C6, 8, 12, 18)/Silica Nanohybrids via in situ generated nanofillers for use as a dual function organonanofiller

AbstractFour types of copolymer-silica nanocomposites have been prepared via ring-opening grafting of γ-aminopropyltrimethoxysilane (APTS) as reactive coupling agent onto preformed copolymers of maleic anhydride (MA) with 1-hexene, 1-octene, 1-dodecene and 1-octadecene and in situ hydrolysis (polycondensation) of side-chain ethoxysilane groups and tetraethoxysilane as a precursor in the presence of HCl catalyst. The copolymers of MA with 1-hexene, 1-octene and 1-dodecene were synthesized by free radical polymerization and another MA copolymer with 1-octadecene was supplied commercially as matrix copolymer. Chemical/physical structures, thermal behavior and morphology investigations of the generated hybrids were performed by FTIR, 13C, 29Si-NMR, TGA, SEM and TEM analysis methods. Nano-level hybridization through covalent bonding (amidization) between the anhydride unit of copolymers and amine group of APTS was observed, and nano-silica networks (hydrolysis) were obtained through acid catalyzed co-polycondensation of TEOS and ethoxysilane fragments from both coupling agent and precursor. Agreeing with 29Si-NMR and TGA quantitative analysis results, the degree of hydrolysis of ethoxysilane groups varied from 51.0 to 60.9%, and the content of in situ generated silica particles was found to be around 70.7-75.7%. Thermal properties and thermal stability of the obtained hybrids were found to be enhanced with silica content. SEM analysis confirmed the formation of nanostructural hybrids with relatively fine distributed nanoparticles. TEM analyses of all the nanohybrids indicate the formation of spherical morphologies. These novel copolymer hybrids are expected to be a promising and efficient organonanofiller for the preparation of polymer nanocomposites with both dual functionality and compatibilizer effects. Graphical AbstractPoly(MA-alt-α-olefin)/silica nanohybrids were obtained by an in situ sol–gel process of TEOS via nano-level hybridization as promising and effective organo nano-fillers.