Filtreler
Filtreler
Bulunan: 156 Adet 0.006 sn
Koleksiyon [20]
Tam Metin [2]
Yayın Türü [7]
Yazar [19]
Yayın Yılı [20]
Konu Başlıkları [20]
Yayıncı [20]
Yayın Dili [2]
Dergi Adı [20]
Araştırmacılar
Yayınlar
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

Makale | 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

Free radical crosslinking copolymerization. Gelation behavior of macromonomeric azoinitiators versus macrocrosslinkers

Yıldız, Ufuk | Hazer, Baki

Makale | 1998 | Macromolecular Chemistry and Physics199 ( 2 ) , pp.163 - 168

In order to evaluate the gelation behavior of macromonomeric azoinitiators (MIMs), the free radical polymerization of MIM and macrocrosslinkers (MCRs) have been compared. MIMs were synthesized by the reaction between 4,4'-dicyano-4,4'-azovaleryl chloride and poly(ethylene glycol)s PEG-400, -1000, -1500, -2000 and 4-vinylbenzyl chloride. MCRs were obtained by vinylation of both hydroxyl ends of PEG samples with 4-vinylbenzyl chloride. Bulk copolymerization of styrene with MIMs or MCRs in the concentration range between 2.91 and 31.50 wt.-% at 70°C for 3 h gave PSt-PEG networks. The gelation behavior of MIM was remarkably different fr . . .om that of MCR. In each case, gel fractions and swelling ratios of the gels depend on the molecular weights of the PEG sequences. Critical minimum concentrations for the onset of gelation were determined as 5, 8, 10 and 10 wt.-% for MIMs containing PEG units with molecular weight 400, 1000, 1500 and 2000, and 6, 12, 18 and 19 wt.-% for MCRs containing PEG units with the same molecular weights as above. Below those concentrations no network is formed. The critical minimum values for the onset of gelation were also obtained from homo- and copolymerization of partially vinylized MIMs with styrene 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

Makale | 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

Simple production experiment of poly (3-hydroxy butyrate) for science laboratories and its importance for science process skills of prospective teachers

Koray, Özlem | Köksal, Mustafa Serdar | Hazer, Baki

Makale | 2010 | ENERGY EDUCATION SCIENCE AND TECHNOLOGY PART B-SOCIAL AND EDUCATIONAL STUDIES2 ( 01.Feb ) , pp.39 - 54

Poly (3-hydroxybutyrate), PHB, is a biocompatible and biodegradable polymer accumulated in microorganism cells as a reserve material. PHB production in biotechnology laboratories has been carried out by using expensive instruments such as autoclave, a large thermostatted shaker, a freeze dryer, and an automatic refrigerated centrifuge. A very simple method of PHB production with Alcaligenes eutrophus for use in science teaching freshman laboratory is reported in this article. The study was conducted with 6 prospective elementary teachers. An ordinary glass 1 L jar, a 4L pressure cooker and thermostate for aquariums were used in ferm . . .entation process of the bacterium in nutrient solution containing table sugar as a substrate. In conclusion, the thermal and characterization data confirmed the PHB structure. Science Process Skills are investigated in this study. Qaulitative method was used to acquire data and analyze the science process skills experienced by the students in the experiment. The article discusses on development of some science process skills during the experimental process and gives suggestions for future use and research Daha fazlası Daha az

Synthesis and characterization of poly(methyl methacrylate-block-ethylene glycol-block-methyl methacrylate) block copolymers by reversible addition-fragmentation chain transfer polymerization

Öztürk, Temel | Göktaş, Melahat | Hazer, Baki

Makale | 2011 | Journal of Macromolecular Science, Part A: Pure and Applied Chemistry48 ( 1 ) , pp.65 - 72

Synthesis of poly(methyl methacrylate-block-ethylene glycol-block-methyl methacrylate) triblock copolymers by reversible addition-fragmentation chain transfer (RAFT) by using a novel dual macro initiator (RAFT-agent) is reported. RAFT-agent is obtained from potassium salt of the ethyl xanthegonate and the terminally brominated poly(ethylene glycol) (Br-PEG-Br) which is synthesized by the reaction of poly(ethylene glycol) [PEG] with Mn= 3000 Dalton and 3-bromopropionyl chloride. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the polymerization reaction are evaluate . . .d. The characterization of the products is achieved using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), gel-permeation chromatography (GPC), thermogravimetric analysis (TGA), and fractional precipitation () techniques. Molecular weights of the polymers obtained from GPC agreed with the theoretical values. RAFT polymerization is used to control the polymerization of MMA over a broad range of molecular weights. Copyright © Taylor & Francis Group, LLC Daha fazlası Daha az

Synthesis and characterization of novel comb-type amphiphilic graft copolymers containing polypropylene and polyethylene glycol

Balcı, Murat | Allı, Abdulkadir | Hazer, Baki | Güven, Olgun | Cavicchi, Kevin | Çakmak, Mükerrem

Makale | 2010 | Polymer Bulletin64 ( 7 ) , pp.691 - 705

Polymerization of methyl methacrylate and its copolymerization with epsilon-caprolactone catalyzed by isobutylalumoxane catalyst

Wu, Bin | Lenz, Robert W. | Hazer, Baki

Makale | 1999 | MACROMOLECULES32 ( 20 ) , pp.6856 - 6859

WOS: 000083003300061

Increased diversification of polyhydroxyalkanoates by modification reactions for industrial and medical applications

Hazer, Baki | Steinbüchel, Alexander

Makale | 2007 | Applied Microbiology and Biotechnology74 ( 1 ) , pp.1 - 12

A wide range of diverse polyhydroxyalkanoates, PHAs, is currently available due to the low substrate specificity of PHA synthases and subsequent modifications by chemical reactions. These polymers are promising materials for a number of different applications due to their biocompatibility and biodegradability. This review summarizes the large variability of PHAs regarding chemical structure and material properties that can be currently produced. In the first part, in vivo and in vitro biosynthesis processes for production of a large variety of different PHAs will be summarized with regard to obtaining saturated and unsaturated copol . . .yesters and side chain functionalized polyesters, including brominated, hydroxylated, methyl-branched polyesters, and phenyl derivatives of polyesters. In the second part, established chemical modifications of PHAs will be summarized as that by means of grafting reactions and graft/block copolymerizations, as well as by chlorination, cross-linking, epoxidation, hydroxylation, and carboxylation, reactions yield further functionalized PHAs. © 2006 Springer-Verlag Daha fazlası Daha az

Novel pH responsive biodegradable heterograft copolymers

Oruç, Olgu | Hazer, Baki | Öztürk, Temel

Bildiri | 2014 | ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY247 , pp.1 - 12

247th National Spring Meeting of the American-Chemical-Society (ACS) -- MAR 16-20, 2014 -- Dallas, TX WOS: 000348457604700

Synthesis and characterization of the novel thermoresponsive conjugates based on Poly(3-hydroxy alkanoates)

Toraman, Tuğba | Hazer, Baki

Makale | 2014 | Journal of Polymers and the Environment22 ( 2 ) , pp.159 - 166

Novel thermoresponsive polymer conjugates based on microbial polyesters and poly-N-isopropyl acryl amide, PNIPAM, have been reported. The unsaturated poly-3-hydroxy alkanoates, poly (3-hydroxy undecenoate), PHU, and 1:1 mixture of 10-undecenoic acid and soy oil acids, PHU-Sy, were brominated by using bromine in the dark, at room temperature. Brominated PHAs were transformed to macro reversible addition-fragmentation chain transfer (RAFT) agents via the substitution reaction with potassium ethyl xanthate. RAFT polymerization of N-isopropyl acryl amide, NIPAM, was initiated by the PHA-derivative containing xanthate pendant groups in o . . .rder to obtain brush type PHA-g-PNIPAM thermo responsive amphiphilic graft copolymers. The water uptake of the PHU-g-PNIPAM and PHU-Sy-g-PNIPAM amphiphilic graft copolymers changed from 50 % to completely soluble in water. Structural and thermal characterization of the novel conjugates were carried out by using 1H NMR, GPC, DSC and TGA techniques. Graphical Abstract: [Figure not available: see fulltext.] © 2014 Springer Science+Business Media New York Daha fazlası Daha az

Synthesis of PNIPAM-PEG Double hydrophilic polymers using oleic acid macro peroxide initiator

Hazer, Baki | Ayyıldız, Elif | Bahadır, Faruk

Makale | 2017 | JOURNAL OF THE AMERICAN OIL CHEMISTS SOCIETY94 ( 9 ) , pp.1141 - 1151

This work refers to the synthesis of a new double hydrophilic thermo-responsive polymer using fatty acid macroperoxide initiator, N-isopropyl acryl amide (NIPAM) and polyethylene glycol with two primary amine ends (PEGNH2). For this purpose, oleic acid was spread out onto a petri dish and exposed to air oxygen at room temperature for 2 months. The obtained fatty acid macro-peroxide initiator was used in the free radical polymerization of NIPAM in the presence of PEGNH2. Poly oleic acid-g-PNIPAM-g-PEG graft copolymers were successfully obtained. Lower critical solution temperature (LCST) of the graft copolymer was determined by using . . . UV-Vis spectrometry with a sensible heating unit. Morphology of the fractured surface of the double hydrophilic polymers was visualized by using SEM micrographs. Graft copolymers with LCST close to body temperature were obtained by changing PEG inclusion. Structural characterization, thermal analysis and size exclusion chromatography measurements of the obtained products were done Daha fazlası Daha az

Covalent immobilization of lipase onto amine functionalized polypropylene membrane and its application in green apple flavor (ethyl valerate) synthesis

Bayramoğlu, Gülay | Hazer, Baki | Altıntaş, Begüm | Arıca, M. Yakup

Makale | 2011 | Process Biochemistry46 ( 1 ) , pp.372 - 378

In this study, a functionalized hydrophobic polypropylene chloride membrane (PPC) was prepared by the amination of chlorinated polypropylene with hexamethylene diamine (APP). The PPC and APP membranes were characterized using SEM, FTIR and contact angle studies. The aminated polypropylene (APP) membrane was used for covalent immobilization of Candida rugosa lipase via glutaraldehyde coupling. The retained activity of the immobilized lipase was 76%. Kinetic analysis shows that the dependence of lipolytic activity of both free and immobilized lipase on tributyrin substrate concentration can be described by Michaelis-Menten model. The . . .estimated apparent Km values for the free and immobilized lipase were 2.9 and 8.4 mM, respectively. The Vmax values of free and immobilized enzymes were calculated as 926 and 741 U/mg enzyme, respectively. Optimal temperature was 5 °C higher for immobilized enzyme than that of the free enzyme. Thermal and storage stabilities were found to be increased upon immobilization. Finally, the immobilized lipase was used for the production of green apple flavor (i.e., ethyl valerate) in hexane medium. © 2010 Elsevier Ltd. All rights reserved Daha fazlası Daha az


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