Deniz Sinirlioglu

Preparation and characterization of stable cross-linked enzyme aggregates of novel laccase enzyme from Shewanella putrefaciens and using malachite green decolorization

A novel type laccase from Shewanella putrefaciens was identified, expressed in Escherichia coli, characterized, prepared in cross-linked enzyme aggregates (CLEA) for industrial applications and investigated of decolorization activity on malchite green dye. Enzyme characterization was investigated by enzyme assay, SDS-PAGE and other biochemical reactions. Moreover, cross-linked enzyme aggregates were prepared and characterized. Saturated ammonium sulphate solution was used as the precipitating agent and cross linked with glutaraldehyde. These CLEA-laccase aggregates showed more catalytic efficiency and more stabilities compared to free laccase against harsh conditions of thermal and chemical agents as well as high reusability. Also it showed more decolorization ability. These results suggest that this CLEA is potentially usable in industrial applications.

Preparation of Thin Films from New Azolic Copolymers and Investigation of Their Membrane Properties

The preparation and thermal, morphological, electrochemical and proton conducting properties analysis of new azolic copolymers based on 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and 5-(methacrylamido)tetrazole) (MTet) were performed throughout this work. MTet monomer, prepared by the reaction of methacryloyl chloride with 5-aminotetrazole, was copolymerized with AMPS via conventional free radical copolymerization at different monomer feed ratios to achieve poly(MTet-co-AMPS) copolymer membranes. The obtained copolymer membranes were analyzed by FTIR, 1H-NMR, thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), Elemental Analysis (EA), Cyclic Voltammetry (CV), and Impedance Spectroscopy. The composition of copolymers was determined via elemental analysis (EA). TGA demonstrated that the copolymer electrolyte membranes are thermally stable up to approximately 250°C. The appearance of a single Tg in the DSC curves verified the homogeneity of the membranes. CV curves demonstrated the oxidative stability of the samples in 3 V region. The methanol permeabilities of S1, S2 and S3 copolymers were determined as 1.60×10−9 mol cm−2 s−1, 2.71×10−9 mol cm−2 s−1 and 3.32×10−9 mol cm−2 s−1, respectively, which were comparable with that of Nafion 112 (1.89×10−9 mol cm−2 s−1). In the anhydrous conditions, the maximum proton conductivity was determined as 0.009 Scm−1 at 150°C for poly(MTet-co-AMPS) (S3). The proton conductivity and methanol permeability of poly(MTet-co-AMPS) copolymer membranes increased gradually with the increase of AMPS content. These results suggested that the poly(MTet-co-AMPS) copolymer membranes were particularly promising to be used as proton exchange membranes in PEMFCs.

An Investigation of Proton Conductivity of Vinyltriazole-Grafted PVDF Proton Exchange Membranes Prepared via Photoinduced Grafting

Proton exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for clean and efficient power generation in the twenty-first century. In this study, high performance of poly(vinylidene fluoride) (PVDF) and proton conductivity of poly(1-vinyl-1,2,4-triazole) (PVTri) were combined in a graft copolymer, PVDF-g-PVTri, by the polymerization of 1-vinyl-1,2,4-triazole on a PVDF based matrix under UV light in one step. The polymers were doped with triflic acid (TA) at different stoichiometric ratios with respect to triazole units and the anhydrous polymer electrolyte membranes were prepared. All samples were characterized by FTIR and 1H-NMR spectroscopies. Their thermal properties were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA demonstrated that the PVDF-g-PVTri and PVDF-g-PVTri-(TA)x membranes were thermally stable up to 390°C and 330°C, respectively. NMR and energy dispersive X-ray spectroscopy (EDS) results demonstrated that PVDF-g-PVTri was successfully synthesized with a degree of grafting of 21%. PVDF-g-PVTri-(TA)3 showed a maximum proton conductivity of Scm−1 at 150°C and anhydrous conditions. CV study illustrated that electrochemical stability domain for PVDF-g-PVTri-(TA)3 extended over 4.0 V.

Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

Synthesis of fluorinated amphiphilic block copolymers via atom transfer radical polymerization (ATRP) and Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) was demonstrated. First, a PEGMA and MMA based block copolymer carrying multiple side-chain acetylene moieties on the hydrophobic segment for postfunctionalization was carried out. This involves the synthesis of a series of P(HEMA-co-MMA) random copolymers to be employed as macroinitiators in the controlled synthesis of P(HEMA-co-MMA)-block-PPEGMA block copolymers by using ATRP, followed by a modification step on the hydroxyl side groups of HEMA via Steglich esterification to afford propargyl side-functional polymer, alkyne-P(HEMA-co-MMA)-block-PPEGMA. Finally, click coupling between side-chain acetylene functionalities and 2,3,4,5,6-pentafluorobenzyl azide yielded fluorinated amphiphilic block copolymers. The obtained polymers were structurally characterized by 1H-NMR, 19F-NMR, FT-IR, and GPC. Their thermal characterizations were performed using DSC and TGA.

Effect of hexagonal boron nitride on poly(vinyl phosphonic acid) composite polymer electrolytes for fuel cells

In this work, hexagonal boron nitride nanoparticles were used as inorganic fillers, which increase the mechanical and thermal stabilities as well as the proton conductivity of the proton conducting composite membranes prepared by blending of poly(vinyl phosphonic acid) and hexagonal boron nitride. Thermo gravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to 200°C. Scanning electron microscopy analysis indicated the homogeneous distribution of boron nitride nanoparticles in the polymer matrix. The crystallinity of the membranes was characterized by using X-ray Diffraction. X-ray patterns support semi-crystalline nature of the composite materials.