Filtreler
Filtreler
Bulunan: 157 Adet 0.002 sn
Koleksiyon [20]
Tam Metin [2]
Yayın Türü [4]
Yazar [20]
Yayın Yılı [20]
Konu Başlıkları [20]
Yayıncı [20]
Yayın Dili [2]
Dergi Adı [20]
Dispersion polymerization of styrene and methyl methacrylate initiated by macromonomeric azoinitiator

Yıldız, Ufuk | Hazer, Baki

Article | 1999 | Angewandte Makromolekulare Chemie265 , pp.16 - 19

The free radical dispersion polymerization of styrene (St) and methyl methacrylate (MMA) initiated by poly(oxyethylene) (PEO) macroazoinimer (MIM-400) in water/ethanol, was investigated at three different temperatures (50, 60 and 80°C) for seven polymerization times (3, 6, 9, 12, 24, 36 and 48 h). PSt-PEO and PMMA-PEO networks were obtained. In each case, polymer gel fractions depend on the polymerization temperature and polymerization time. With the same initial concentration of MIM-400, maximum gel fraction was found at 80 wt.-% with St copolymerization while 100 wt.-% in case of copolymerization with MMA at 80°C for 48 h. © Wiley . . .-VCH Verlag GmbH, 1999 Daha fazlası Daha az

Synthesis of polytetrahydrofuran macromonomeric peroxy initiators via cationic polymerization

Savaşkan, Sevil | Volga, Cüneyt | Hazer, Baki

Article | 1998 | Designed Monomers and Polymers1 ( 1 ) , pp.111 - 119

Polytetrahydrofuran macromonomeric initiators (poly-THF-inimer) were synthesized via cationic polymerization of THF, initiated by the combination of AgSbFe 6 and mono-, di-, or tetra-bromomethyl benzoyl peroxides, followed by termination with methacrylate anion. The macroinimers were characterized by 1 H-NMR and GPC techniques. Copolymerization of poly-THF-inimers with methyl methacrylate (MMA) gave crosslinked block copolymers. Sol-gel analysis and swelling measurements of the crosslinked product are also reported.

Synthesis of the new cation exchange resins having poly(styrene-caprolactone) units

Yılmaz-Savaşkan, Sevil | Özbayrak, Hulisi | Hazer, Baki

Article | 1997 | TURKISH JOURNAL OF CHEMISTRY21 ( 4 ) , pp.270 - 276

The crosslinked polystyrene-polycaprolactone, PS-PCL-, block copolymers were prepared by the copolymerization of styrene and poly(caprolacton dimethylmethacrylate) (PCL-DM). The molecular weights of polycaprolactone, PCL, PCL-DM were 1250 and 2000. The swelling in H2O or CHCl3 of the sulfonate and unsulfonated block copolymers were determined under comparable conditions and investigated. The capacities of the obtained ion exchange resins were 1.31 and 1.10 meq/g.

Reactions of anionic living polymers with bromomethyl-functionalized benzoyl peroxides

Hazer, Baki | Hirao, Akira | Volga, Cüneyt

Article | 1999 | Macromolecular Chemistry and Physics200 ( 1 ) , pp.71 - 76

In order to synthesize benzoyl peroxide functionalized polystyrene (PSt), polyisoprene (PI) and poly(methyl methacrylate) (PMMA), anionic living PSt, PI, and PMMA were allowed to react with an excess amount of 4-(bromomethyl)benzoyl tert-butyl peroxide (BMtB) or bis[3,5-bis(bromomethyl)benzoyl] peroxide (BDBP) in tetrahydrofuran (THF) at -78°C. The results indicate that coupling reactions leading to dimers are significant during the reaction. Dimer formation was avoided when the living polystyrene was modified to the alcoholate anion by reaction with ethylene oxide (EO). © Wiley-VCH Verlag GmbH, 1999.

Synthesis and characterization of poly(Ɛ-caprolactone-co-ethylene glycol) star-type amphiphilic copolymers by “click” chemistry and ring-opening polymerization.

Öztürk, Temel | Kılıçlıoğlu, Ali | Savaş, Bedrettin | Hazer, Baki

Article | 2018 | Journal of Macromolecular Science, Part A: Pure and Applied Chemistry55 ( 8 ) , pp.588 - 594

The synthesis of poly(?-caprolactone-co-ethylene glycol) AAB star-type amphiphilic copolymers were carried out by use of a “click” chemistry reaction to block propargyl polyethylene glycol (propargyl-PEG) to terminally azide poly(?-caprolactone) (PCL-N3). For this purpose, propargyl-PEG was synthesized by the reaction of PEGs (3000 Da, 2000 Da, 1500 Da, and 1000 Da) and propargyl chloride. Terminally chloride poly(?-caprolactone) (PCL-Cl) was carried out by means of ring-opening polymerization (ROP) of ?-caprolactone (CL) and 3-chloro-1,2-propanediol. Synthesis of PCL-N3 was obtained by the chemical interaction of PCL-Cl and sodium . . .azide. By reacting propargyl-PEG and PCL-N3, the star-type amphiphilic copolymers were obtained. The characterization of products was accomplished by using multiple instruments including 1H-NMR, FT-IR, GPC, TGA, contact angles, and elemental analysis techniques. © 2018, © 2018 Taylor & Francis Group, LLC Daha fazlası Daha az

Synthesis of microbial elastomers based on soybean oil. Autoxidation kinetics, thermal and mechanical properties

Hazer, Baki | Hazer, Derya Burcu | Çoban, Burak

Article | 2010 | Journal of Polymer Research17 ( 4 ) , pp.567 - 577

Microbial bioelastomers prepared by the autoxidation of the unsaturated medium-long chain length copoly- 3-hydroxyalkanoate's (mlcl-PHAs) based on soybean oily acids (Sy) have been reported. Pseudomonas oleovorans were grown on a series of the mixture of octanoic acid (OA) and Sy with the weight ratio of 20:80, 28:72 and 50:50 in order to obtain unsaturated mlcl-copolyesters coded PHO-Sy-2080, PHO-Sy-2872, and PHO-Sy-5050, respectively. The microorganism was also grown on the mixture of Sy and 10-undecenoic acid (UA) with the weight ratio of 50:50 to obtain unsaturated copolyester coded PHU-Sy-5050. The PHAs obtained were characteri . . .zed by 1H NMR and GC-MS techniques. Double bond contents of the unsaturated PHAs obtained were varying between 0.8 to 20 mol %. Autoxidation of the unsaturated copolyesters were carried out on exposure to air at room temperature in order to obtain new biomaterials whose mechanical strength was improved. Autoxidation kinetics, shelf life, mechanical and thermal properties of these biomaterials were evaluated Daha fazlası Daha az

Novel Enzymatic Rhodium Modified Poly(styrene-g-oleic amide) Film Electrode for Hydrogen Peroxide Detection

Kılıç, Muhammet Samet | Korkut, Şeyda | Hazer, Baki

Article | 2017 | Electroanalysis29 ( 10 ) , pp.2377 - 2384

Newly synthesized poly(styrene-g-oleic amide) was coated onto a rhodium nanoparticle modified glassy carbon (GC) surface for the fabrication of horseradish peroxidase based biosensor used for hydrogen peroxide detection. The rhodium modifed electrode presented ten times higher signal than unmodified electrode even at low elecrtroactive enzyme quantity by enhancing the electron transfer rate at the applied potential of -0.65 V. The biosensor designed by under the optimized rhodium electrodeposition time exhibited a fast response less than 5 s, an excellent operational stability with a relative standard deviation of 0.6 % (n=6), an ac . . .curacy of 96 % and a large linear range between 50 µM and 120 mM for hydrogen peroxide. Detection limit and the sensitivity parameters were calculated to be 44 µM and 57 µA mM-1 cm-2, respectively by preserving its entire initial response up to the 15 days, while only 20 % of its initial response was lost at the end of one month. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei Daha fazlası Daha az

Effect of the composition of methanol-water mixtures on tacticity of poly(N-ethylacrylamide) gel

Biswas, Chandra Sekhar | Sulu, Elvan | Hazer, Baki

Article | 2015 | Journal of Applied Polymer Science132 ( 12 ) , pp.2377 - 2384

Two series of macroporous poly(N-ethylacrylamide) (PNEAM) gels are synthesized in different composition of methanol-water mixtures (xm=0, 0.06, 0.13, 0.21, 0.31, and 0.43; where xm=mole fraction of methanol) in presence as well as in the absence of 0.1M Y(OTf)3 Lewis acid as additive. The gels synthesized in the absence of Lewis acid are atactic and in the presence of the same are isotactic. Synthesis of the corresponding linear PNEAM homopolymers shows that, the isotacticity (meso dyad, %) of the resulted polymers increases for the gels prepared in the presence of Lewis acid (LA) and remains constant for the gel prepared in the abs . . .ence of LA, respectively, with the increase in the concentration of the synthesis solvent methanol. SEM micrographs reveal that, the hydrogels synthesized in the presence of LA are more porous than the gels prepared in the absence of LA. Swelling ratio of all the hydrogels decreases with the increase in the temperature and LA gels show higher swelling ratio values than non LA gels (NLA). Deswelling rate of the hydrogels prepared in methanol-water mixture in presence of LA is faster than the hydrogels prepared in absence of LA. Moreover, reswelling rate increases with increase in the isotacticity of the PNEAM segment in the gel. All these results have been explained on the basis of the formation of highly porous hydrogels with higher isotactic PNEAM chain segment in the presence of LA in methanol-water mixtures. © 2014 Wiley Periodicals, Inc Daha fazlası Daha az

Poly(N-isopropylacrylamide) thermoresponsive cross-linked conjugates containing polymeric soybean oil and/or polypropylene glycol

Allı, Abdulkadir | Hazer, Baki

Article | 2008 | European Polymer Journal44 ( 6 ) , pp.1701 - 1713

Synthesis, characterization and solution properties of a new series of the PNIPAM-soybean oil and/or polypropylene glycol, PPG, conjugates (conjugates also referred to as co-networks) have been described. For this purpose free radical polymerization of NIPAM monomer was initiated by macroinitiators based on PSB and/or PPG in order to obtain PSB-g-PNIPAM, PPG-g-PNIPAM and PSB-g-PPG-g-PNIPAM cross-linked graft copolymers. The autooxidation of soybean oil under air at room temperature rendered waxy soluble polymeric soybean oil peroxide associated with cross-linked parts. The soluble polymeric oil macro-peroxide isolated from the cross . . .-linked part was used to initiate the free radical polymerization of NIPAM to give PSB-g-PNIPAM cross-linked copolymer. To obtain PPG-macromonomeric initiator, PPG-MIM, PPG-bis amino propyl ether with Mn 400 (or 2000) Dalton was reacted with 4,4'-azo bis cyanopentanoyl chloride and methacryloyl chloride, respectively. PPG-MIM also initiated the free radical polymerization of NIPAM at 80 °C to yield PPG-g-PNIPAM cross-linked thermoresponsive product. In order to obtain PSB-g-PPG-g-PNIPAM cross-linked triblock copolymer, NIPAM was polymerized by using the mixture of two macroinitiators, PSB and PPG-MIM. PSB contents in the graft copolymers were calculated via elemental analysis of nitrogen in graft copolymers. Thermal analysis, SEM, FTIR and 1H NMR techniques were used in the characterization of the products. The effect of polymeric soybean oil, PSB, and/or PPG on the thermal response rate of poly(N-isopropylacrylamide, PNIPAM, cross-linked-graft copolymers swollen in water has been investigated by means of swelling-deswelling and drug release behaviors against to temperature change. Lower critical solution temperatures (LCST) of the cross-linked PNIPAM conjugates (conjugates also referred to as co-networks) were determined from the curves of swelling degrees versus solution temperatures. The response temperature of the hydrophobically modified PNIPAM conjugates was reduced to 27 °C, 23 °C and 27 °C for PSB-g-PNIPAM, PPG-g-PNIPAM and PSB-g-PPG-g-PNIPAM, respectively. We have found that the graft copolymers were not pH-responsive. In addition, higher pH ranges cause the hydrolysis of the PSB ester linkages, quickly and makes the cross-linked graft copolymers soluble. The fastest shrinking of the gels was observed by loosing water between 65% and 98% at 50 °C. Methyl orange (MO), was used as a model drug, loaded into cross-linked graft copolymers to examine and compare the effects of controlled release at lower and higher temperatures of lower critical solution temperature (LCST). © 2008 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Power improvement of enzymatic fuel cells used for sustainable energy generation

Korkut, Şeyda | Kılıç, Muhammet Samet

Article | 2016 | Environmental Progress and Sustainable Energy35 ( 3 ) , pp.859 - 866

Poly(3-thiopheneacetic acid-co-3-methylthiophene) conductive polymer was electrosynthesized with ferrocene and used for an enzymatic fuel cell including glucose oxidase and bilirubin oxidase enzymes. The system was operated in a single-compartment and membrane-less cell by using glucose as fuel. Detailed optimization ensured to achieve considerable power output to generate sustainable energy from municipal wastewater as a renewable fuel source. Maximum power density of 1 µW/cm2was generated at a cell voltage of +0.56 V in 100 mM, pH 7.4 phosphate buffer with the addition of 10 mM synthetic glucose. The working electrodes could harve . . .st glucose readily found in the municipal wastewater of Zonguldak City in Turkey by generating a power density of 4 µW/cm2for the municipal wastewater sample. In this way, the organic pollutants in wastewater could be evaluated by converting them into the electrical energy using an enzymatic fuel cell for the first time. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 859–866, 2016. © 2015 American Institute of Chemical Engineers Environ Pro Daha fazlası Daha az

Chemical modification of chlorinated microbial polyesters

Arkın, Ali Hakan | Hazer, Baki

Article | 2002 | Biomacromolecules3 ( 6 ) , pp.1327 - 1335

Chlorination of microbial polyesters poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyoctanoate) (PHO) was carried out by passing chlorine gas through their solutions. The chlorine contents in chlorinated PHB (PHB-Cl) and chlorinated PHO (PHO-Cl) were between 5.45 and 23.81 wt % and 28.09 and 39.09 wt %, respectively. Molecular weights of the chlorinated samples were in the range of between one-half to one-fourth of the original values because of hydrolysis during the chlorination process. Thermal properties of the PHO-Cl were dramatically changed with an increase in its glass transition (Tg = 2 °C) and the melting transition (Tm). T . . .he Tg of PHB-Cl varied from -20 to 10 °C, and its Tm decreased to 148 °C. The chlorinated poly(3-hydroxyalkanoate)s (PHA-Cl) were converted to their corresponding quaternary ammonium salts (PHA-N+R3), sodium sulfate salts (PHA-S), and phenyl derivatives (PHA-Ph). Cross-linked polymers were also formed by a Friedel-Crafts reaction between benzene and PHA-Cl. The modified PHO derivatives were characterized by 1H NMR and 13C NMR spectrometry, Fourier transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry techniques Daha fazlası Daha az

Silver nanoparticle incorporation effect on mechanical and ther at properties of denture base acrylic resins

Köroğlu, Ayşegül | Şahin, Onur | Kürkçüoğlu, Işın | Dede, Doğu Ömür | Özdemir, Tonguc | Hazer, Baki

Article | 2016 | JOURNAL OF APPLIED ORAL SCIENCE24 ( 6 ) , pp.590 - 596

Objective: The aim of the present study was to evaluate the mechanical and thermal characteristics of two denture base acrylic resins containing silver nanoparticles (AgNPs). Material and Methods: Two different acrylic denture base resins (heat-polymerized and microwave polymerized) containing 0.3, 0.8 and 1.6 wt% AgNPs were evaluated for flexural strength, elastic modulus and impact strength. The glass transition temperature (Tg) and relative heat capacity (Cp) of the samples were determined from the Differential Scanning Calorimetry (DSC) results. For statistical analysis, two-way ANOVA and Tukey-HSD tests were performed. Results: . . . Addition of 0.8% and 1.6% AgNPs in microwave polymerized resin significantly decreased the transverse strength and elastic modulus. In terms of impact strength, the addition of AgNPs has no effect on both resin groups. Glass transition temperature (Tg) was decreased with the addition of AgNPs for both denture base resins. Conclusions: The incorporation of AgNPs, generally used for antimicrobial efficiency, affected the transverse strength of the denture base acrylic resins depending on the concentration of nanoparticles. Tg was decreased with the addition of AgNPs for both denture base resins Daha fazlası Daha az

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