Browsing by Author "Hazer, Baki"

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Free Radical Polymerization of Dimethyl Amino Ethyl Methacrylate Initiated by Poly(3-Hydroxybutyrate Macroazo Initiator: Thermal and Physicochemical Characterization
(Springer, 2023) Hazer, Baki; Modjinou, Tina; Langlois, Valerie; Goktas, Melahat; Tasci, Fulya; Ashby, Richard D.; Zhang, Baozhong
A novel macro intermediate based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was synthesized for use in the copolymerization with dimethyl amino ethyl methacrylate (DMAEMA). Methyl amino ethanol was reacted with PHBHHx to prepare a dihydroxy terminated polyester. The hydroxyl ends of the obtained PHBHHx derivatives were capped with 4,4'-azobis cyanopentanoic acid to obtain the PHBHHx macroazo initiator (PHBHHx-AI) for free radical copolymerization of DMAEMA at 70(o)C. A steady increase in DMAEMA units in the synthesized block copolymer as a function of time was observed. The overall rate constants for the free radical polymerization of DMAEMA initiated by PHBHHx-AI was k = 2.33 x 10(- 4) Lmol(-1)s(-1). Block copolymers were characterized using the (1) H NMR, FTIR, DSC and TGA techniques.
One-Step Synthesis of Triarm Block Copolymers by Simultaneous Atom Transfer Radical and Ring-Opening Polymerization
(Springer, 2016) Ozturk, Temel; Yavuz, Mahmut; Goktas, Melahat; Hazer, Baki
One-step synthesis of poly(MMA-b-CL) triarm block copolymers was carried out by atom transfer radical polymerization of methyl methacrylate (MMA) and ring-opening polymerization of epsilon-caprolactone (CL) using 3-chloro-1,2-propanediol trifunctional initiator. The triarm block copolymers comprising one poly-MMA arm and two poly-CL arms were synthesized by changing some polymerization conditions such as monomer/initiator concentration, polymerization time. The effect of the reactions conditions on the polydispersity and molecular weights was also investigated. The block lengths of the block copolymers were calculated by using H-1-nuclear magnetic resonance (H-1-NMR) spectrum. It was observed that the block length could be altered by varying the monomer and initiator concentrations. The characterization of the products was achieved by using H-1-NMR, Fourier-transform infrared spectroscopy, gel-permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and fractional precipitation techniques.
Synthesis and Characterization of Graft Copolymers Based on Polyepichlorohydrin Via Reversible Addition-Fragmentation Chain Transfer Polymerization
(Taylor & Francis inc, 2016) Ozturk, Temel; Kaygin, Oguz; Goktas, Melahat; Hazer, Baki
In this study, synthesis of poly(epichlorohydrin-g-methyl methacrylate) graft copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization was reported. For this purpose, epichlorohydrin was polymerized by using HNO3 via cationic ring-opening mechanism. A RAFT macroinitiator (macro-RAFT agent) was obtained by the reaction of potassium ethyl xanthogenate and polyepichlorohydrin. The graft copolymers were synthesized using macro-RAFT agent as initiator and methyl methacrylate as monomer. The synthesis of graft copolymers was conducted by changing the time of polymerization and the amount of monomer-initiator concentration that affect the RAFT polymerization. The effects of these parameters on polymerization were evaluated via various analyses. The characterization of the products was determined using H-1-nuclear magnetic resonance (H-1-NMR), Fourier-transform infrared spectroscopy, gel-permeation chromatography, thermogravimetric analysis, elemental analysis, and fractional precipitation techniques. The block lengths of the graft copolymers were calculated by using H-1-NMR spectrum. It was observed that the block length could be altered by varying the monomer and initiator concentrations.
Synthesis of Poly(styrene)-G Acid) Graft Copolymers Via Reversible Addition/Fragmentation Transfer (Raft) Polymerization Using a Poly Oleic Acid Macro-Raft Agent
(Springer, 2024) Goktas, Melahat; Aykac, Cengiz; Hazer, Baki; Ashby, Richard D.
In this study, a new polymeric oleic acid-derived macro addition/fragmentation transfer agent was utilized to produce a poly(styrene)-g-poly(oleic acid) graft copolymer. The double bond of oleic acid was initially saturated with bromine and the condensation polymerization between the carboxylic acid and the bromide resulted in polyoleic acid with pendant bromide groups. Xanthate groups were exchanged with the bromide groups to obtain the poly(oleic acid) macro RAFT agent (Pole-Xa). Poly(styrene)-g-poly(oleic acid) (PS-g-Pole) graft copolymers were synthesized via reversible addition fragmentation transfer (RAFT) polymerization of styrene and the reaction was evaluated in view of the polymerization kinetics. The effects of polymerization temperature and reaction time on graft copolymer yield, conversion and molecular weight were investigated. In the RAFT polymerization of styrene, the rate constant (k) was found to be 1.83 x 10(-3) L/mol/dk and 7.27 x 10(-4) L/mol/dk for the polymerization temperatures of 80 and 90 degrees C, respectively. The structural characteristics and thermal properties of the obtained products were characterized using FT-IR, H-1-NMR, GPC, TGA, DSC and SEM-EDX.