Browsing by Author "Goktas, Melahat"

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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 and Characterization of Poly(ε-Caprolactone) Thermo-Responsive Block Copolymers Via Raft and Rop Techniques
(Maik Nauka/interperiodica/springer, 2019) Goktas, Melahat; Olgun, Berivan
In this study, well-defined thermo-responsive block copolymers of poly(epsilon-caprolactone)-b-poly(N-isopropylacrylamide) with narrow molecular weight distribution were synthesized in one-step via reversible addition-fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP) methods using dual RAFT-ROP initiator which was obtained via the reaction of 3-chloro-1,2-propanediol with the potassium salt of ethyl xanthogenate. Thermo-responsive block copolymers were obtained in high yield and high molecular weight. The characterization of the products was accomplished by NMR and FTIR spectroscopy, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry. Furthermore, thermo-responsive properties of the copolymers were verified by UV, and fractional precipitation techniques.
One-Step Synthesis and Characterization of the Block-Graft Terpolymer Via Simultaneous Atom Transfer Radical Polymerization (Atrp) and Ring-Opening Polymerization (Rop) Techniques
(indian Acad Sciences, 2022) Goktas, Melahat; Aykac, Cengiz; Ozturk, Temel
In this study, we evaluated cooccurring ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) for simultaneous one-step synthesis of the block-graft terpolymer of E-caprolactone and methyl methacrylate using polyepichlorohydrin (PECH) macroinitiator. For this purpose, the block-graft terpolymer was synthesized by ROP of a lactone and ATRP of a vinyl monomer using the PECH macroinitiator, which is an initiator suitable for both ROP and ATRP in one step. Spectral and chromatographic analyzes prove that the strategy used is successful in the simultaneous one-step preparation of the block-graft terpolymer with controlled molecular weights and narrow distributions.
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 a Brush Type Graft Copolymer Via Raft and "click" Chemistry Methods
(Springer, 2023) Goktas, Melahat; Aykac, Cengiz; Ozturk, Temel
In this study, well-known poly(4-vinylbenzyl-g-ethylene glycol) [P(4-VB-g-EG)] brush type graft copolymer was synthesized by recycling additive/fragmentation chain transfer (RAFT) polymerization and a "click" chemistry method. In the first step, a RAFT agent (CTA) was synthesized for this purpose by the reaction of 2-(2-chloro ethoxy) ethanol and potassium ethyl xanthogenate salt. In the second step, poly(4-vinylbenzyl chloride) [P(4-VBC)] was synthesized by performing RAFT polymerization of 4-vinylbenzyl chloride using a RAFT initiator. In the third step, poly(4-vinylbenzyl-N-3) [P(4-VB-N-3)] was produced by a reaction that synthesized P(4-VBC)] and NaN3. In addition, PEG-propargyl (alkyne-terminated-PEG) was obtained by the reaction between polyethylene glycol (PEG-3000) and propargyl chloride. In the last step, poly(4-VB-g-EG) brush type graft copolymer was obtained by the reaction of PEG-propargyl and poly(4-VB-N-3) via the "click" chemistry method. The synthesized products were characterized utilizing various spectroscopic methods. The DSC result showed that the glass transition temperature value of the brush type graft copolymer was 30 & DEG;C, different from that of the homopolymer. The SEM analysis demonstrated that the surface morphology of the homopolymer and brush type graft copolymers differed. The fact that the brush type graft copolymer has two different decomposition temperatures such as 220 & DEG;C and 410 & DEG;C has been proven by TGA analysis.
Synthesis and Characterization of Block Copolymer: Thermal and Morphological Properties of Sio2-Filled Block Copolymer Nanocomposites
(Springer, 2023) Goktas, Melahat; Aykac, Cengiz; Akinay, Yuksel
With the development of nanotechnology, the production and use of the nanocomposites has been increased. Polymer nanocomposites are among the most widely used nanocomposites. In this study, block copolymer and block copolymer-based polymer nanocomposites were synthesized and evaluated. For this purpose; firstly, poly(beta-butyrolactone)-b-poly(methyl methacrylate) [P(BL-b-MMA)] block copolymers were prepared simultaneously in one-pot by recycling additive/fragmentation chain transfer (RAFT) and ring-opening (ROP) polymerizations using a novel bifunctional RAFT-ROP agent which synthesized by chemical reaction with 3-bromo-1-propanol and potassium ethyl xanthate. Secondly, for the preparation of polymer nanocomposite, SiO2 nanoparticles were added to the prepared block copolymer with a rate of 3 wt% both during the polymerization stage and after the polymerization stage. The synthesized RAFT-ROP agent, block copolymer, and polymer nanocomposites were characterized using spectroscopic methods. The effect of copolymerization reaction conditions on molecular weight and molecular weight distribution (dispersity) was investigated. In one-pot copolymerization processes, relatively high weight copolymers were obtained by changing the copolymerization conditions due to the active centers in the copolymerization environment. The thermal characterization showed that the glass transition temperature of the block copolymer decreases with the addition of SiO2 during the polymerization stage and increases with the addition of SiO2 after the polymerization stage. SEM surface morphologies showed that block copolymer and polymer nanocomposites morphology is different from each other. The difference can be explained by the good dispersion of the block copolymer and SiO2 nanoparticles within each other.
Synthesis and Characterization of Graft Copolymer Hydrogel by "grafting From" Atom Transfer Radical Polymerization Using Brominated Macro Monomeric Initiator and Investigation of Hydrogel Properties
(Springer, 2024) Goktas, Melahat; Aslan, Umran
In this study, poly(e-caprolactone-g-2-hydroxy ethyl methacrylate) [P(CL-g-HEMA)] graft copolymer hydrogels were successfully synthesized through multi-step reactions. For this purpose, firstly, hydroxyl-terminated poly(e-caprolactone) (PCL-OH) was obtained by ring-opening polymerization (ROP) method of e-caprolactone using 3-chlor-1,2-propanediol initiator, which is suitable for ring-opening polymerization method. Then, from the reaction of synthesized PCL-OH and 3-bromopropionyl chloride, a new brominated poly(e-caprolactone) (PCL-Br) was synthesized for use as a functionalized atom transfer radical polymerization (ATRP) initiator. Poly(e-caprolactone-g-2-hydroxy ethyl methacrylate) [P(CL-g-HEMA)] graft copolymer hydrogels were synthesized by "grafting from" atom transfer radical polymerization (ATRP) of 2-hydroxy ethyl methacrylate (HEMA) presence the new synthesized functionalized ATRP initiator (PCL-Br) and hydrogel properties were investigated. The synthesized functionalized initiators and graft copolymer hydrogel were characterized by spectroscopic methods such as 1H-NMR, FT-IR, TGA, DSC and SEM. The observation of two different decomposition temperatures, respectively, from the TGA analysis results may support the formation of the biblock graft copolymer. A glass transition temperature (Tg) of the graft copolymer hydrogel was found by DSC, and this value is between the Tg values of the homopolymers forming the graft copolymer hydrogel. Water swelling values of graft copolymer hydrogels were measured and calculated every 24 h in pure water with pH = 7 at from + 4 to 65 degrees C. Considering the weight of dry graft copolymer hydrogels, it was seen that water was absorbed at most at + 4 degrees C. As the temperature increased, the water absorption or swelling of the hydrogel decreased.
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 and Characterization of Temperature-Responsive Block Copolymers Using Macromonomeric Initiator
(Springer international Publishing Ag, 2020) Goktas, Melahat
Temperature-responsive block copolymers, poly(2-(dimethyl amino)ethyl methacrylate)-b-poly(N-isopropylacrylamide) [PDMAEMA-b-PNIPAM], have been prepared by a combination of the redox polymerization and the reversible addition-fragmentation chain transfer (RAFT) polymerization. For this purpose, poly-N-isopropylacrylamide (PNIPAM-Cl) was acquired by redox polymerization of N-isopropylacrylamide (NIPAM) using 2-(2-chloroethoxy)ethanol and Ce(NH4)(2)(NO3)(6) was used as a catalyst. Poly(DMAEMA-b-NIPAM) temperature-responsive copolymers were prepared via RAFT of 2-(dimethyl amino)ethyl methacrylate) (DMAEMA) in the presence of macromonomeric initiator (macro-CTA) which was obtained via the reaction of PNIPAM-Cl with the potassium salt of ethyl xanthogenate. The synthesized temperature-responsive block copolymer was characterized using multi-instruments and methods such as nuclear magnetic resonance spectroscopy, F(f)ourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, differential scanning calorimetry, scanning electron microscope and UV-Vis.
Synthesis and Characterization of Temperature-Responsive Block Copolymers Using Macromonomeric Initiator (Vol 74, Pg 2297, 2020)
(Springer international Publishing Ag, 2020) Goktas, Melahat
Synthesis and Characterization of Various Block Copolymers Using Pmma-Br Macroinitiator
(Springer international Publishing Ag, 2019) Goktas, Melahat
In this study, block copolymers poly(methyl methacrylate-b-styrene) and poly(methyl methacrylate-b-acrylamide) were synthesized in two steps using a combination of the redox polymerization method and the atom transfer radical polymerization (ATRP) method. For this purpose, polymethyl methacrylate (PMMA-Br macroinitiator) was synthesized by redox polymerization of methyl methacrylate (MMA) and 3-bromo-1-propanol. Ce(NH4)(2)(NO3)(6) was used as a catalyst for the redox polymerization. The syntheses of poly(MMA-b-S) and poly(MMA-b-AAm) block copolymers were carried out by means of ATRP of PMMA-Br macroinitiator, styrene (S), and acrylamide (AAm) at 110 degrees C. The block length of the block copolymers was adjusted by changing various parameters such as monomer and initiator concentrations. The characterization of the products was achieved using multi-instruments and methods such as nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, and fractional precipitation [solvent (THF-mL)/nonsolvent (petroleum ether-mL)] techniques.
Synthesis of Block-Brush Terpolymer Via One-Step Raft-Rop and Grafting To "click" Chemistry Methods
(Springer, 2025) Goktas, Melahat; Aykac, Cengiz
In this contribution, well-defined poly(epsilon-caprolactone-b-4-vinylbenzyl-g-ethyleneglycol) [poly(epsilon-CL-b-VB-g-EG)] block-brush terpolymer was prepared via reversible addition/fragmentation chain transfer (RAFT), ring-opening polymerization (ROP) and grafting to "click" chemistry methods. For this purpose, in the first part, a RAFT agent was obtained by the reaction of 3-chloro-1-propanol and ethylxanthic acid potassium salt for the one-step RAFT-ROP polymerization. In the second part, the poly(epsilon-caprolactone-b-4-vinyl benzyl chloride) [poly(epsilon-CL-b-VBC)] block copolymer was prepared by RAFT polymerization of 4-vinyl benzyl chloride, and ROP of epsilon-caprolactone in the presence of RAFT agent in the one-step. In the third part, the poly(epsilon-caprolactone-b-4-vinyl benzyl-N3) (azide-terminated) was obtained from reaction of the poly(epsilon-CL-b-VBC) block copolymer and NaN3. Finally, the poly(epsilon-CL-b-VB-g-EG) block-brush terpolymer was prepared from the reaction PEG-propargyl, which obtained by the reaction of polyethylene glycol (PEG-3000) with propargyl chloride, and poly(epsilon-CL-b-VB-N3) via the grafting to "click" chemistry method. The structure of the final products was characterized by methods such as GPC, 1H-NMR, FT-IR, DSC, and SEM.
Synthesis of Poly(Methyl Methacrylate)-B Block Copolymer by Redox Polymerization and Atom Transfer Radical Polymerization
(Gadjah Mada Univ, dept Chemistry, 2018) Goktas, Melahat; Deng, Guodong
Poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) [PMMA-b-PNIPAM] block copolymers were obtained by a combination of redox polymerization and atom transfer radical polymerization (ATRP) methods in two steps. For this purpose, PMMA macroinitator (ATRP-macroinitiator) was synthesized by redox polymerization of methyl methacrylate and 3-bromo-1-propanol using Ce(NH4)(2)(NO3)(6) as a catalyst. The synthesis of PMMA-b-PNIPAM block copolymers was carried out by means of ATRP of ATRP-macroinitiator and NIPAM at 60 degrees C. The block copolymers were obtained in high yield and high molecular weight. The characterization of products was accomplished by using multi instruments and methods such as nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, and thermogravimetric analysis.
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.