Browsing by Author "Dincer, Sevil"

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Microwave-assisted green approach for graft copolymerization of l-lactic acid onto starch
(WILEY111 RIVER ST, HOBOKEN 07030-5774, NJ, 2016) Salimi, Kouroush; Topuzogullari, Murat; Dincer, Sevil; Aydin, Halil Murat; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dincer, Sevil
Poly l-lactic acid grafted starch (St-g-PLA) copolymers were directly synthesized under microwave irradiation by using sodium hydroxide (NaOH) and stannous 2-ethyl hexanoate acting as a catalyst, without the use of toxic solvents. The product were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (C-13 CP/MAS NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA-DTG). SEM analysis indicated that microwave heating had a considerable effect on the interfacial adhesion between PLA and starch. Thermogravimetric analysis (TGA-DTG) revealed that copolymers exhibited better thermal stability. Maximum PLA grafting was achieved with the following reaction conditions: 450W microwave power, monomer ratio of 1:5 and 0.4M of NaOH. This study demonstrates that it is possible to obtain St-g-PLA copolymers with better processing characteristics and smaller sizes via microwave-assisted synthesis. The applied procedure is an interesting green synthesis method for the production of biodegradable materials used in a diverse range of applications. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42937.
pH- and temperature-responsive amphiphilic diblock copolymers of 4-vinylpyridine and oligoethyleneglycol methacrylate synthesized by RAFT polymerization
(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2014) Topuzogullari, Murat; Bulmus, Volga; Dalgakiran, Eray; Dincer, Sevil; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü;
Diblock copolymers of 4-vinylpyridine (4VP) and oligoethyleneglycol methyl ether methacrylate (OEGMA) were synthesized for the first time using RAFT polymerization technique as potential drug delivery systems. Effects of the number of ethylene glycol units in OEGMA, chain length of hydrophobic P4VP block, pH, concentration and temperature on the solution behavior of the copolymers were investigated comprehensively. Copolymer chains formed micelles at pH values higher than 5 whereas unimeric polymers were observed to exist below pH 5, owing to the repulsion between positively charged P4VP blocks. The size of the micelles was dependent on the relative length of blocks, P4VP and POEGMA. Thermo-responsive properties of copolymers were investigated depending on the pH and length of P4VP block. The increase in the length of P4VP block decreased the LCST substantially at pH 7. At pH 3, LCST of copolymers shifted to higher temperatures due to the increased interaction of copolymers with water through positively charged P4VP block. (C) 2013 Elsevier Ltd. All rights reserved.
RAFT-mediated synthesis of poly(N-(2-hydroxypropyl)methacrylamide-b-4-vinylpyridine) by conventional and microwave heating
(SPRINGERONE NEW YORK PLAZA, SUITE 4600 , NEW YORK, NY 10004, UNITED STATES, 2013) Ozdemir, Zeynep; Topuzogullari, Murat; İsoglu, Ismail Alper; Dincer, Sevil; 0000-0003-4435-7776; 0000-0001-5085-5814; AGÜ, Yaşam ve Doğa Bilimleri Fakültesi, Biyomühendislik Bölümü; İsoglu, Ismail Alper; Dincer, Sevil
We report the synthesis of N-(2-hydroxypropyl)methacrylamide (HPMA) macroCTA and HPMA-b-4-Vinylpyridine block copolymers via reversible addition-fragmentation chain transfer (RAFT) reaction. Polymerization was carried out in dimethylformamide (DMF) at 70 C using 4-Cyano-4(thiobenzoylthio) pentanoic acid as chain transfer agent and AIBN as an initiator. Control over molecular weight and composition was achieved by altering the CTA, monomer and initiator feed ratio. The controlled living character of the polymerization was verified with pseudo-first-order kinetic plots, a linear increase of the molecular weight with conversion, and low polydispersities (PDIs B 1.2). Effect of microwave heating on the homo- and copolymer formation was investigated and the rates were significantly higher than those observed under conventional heating conditions. These polymerization reactions were in controlled fashion resulting in polymers with low PDIs, too. These polymers have a great potential to be used in developing delivery vehicles and conjugates for further drug or gene delivery applications