Filtreler
Hyperbranched homo and thermoresponsive graft copolymers by using ATRP-macromonomer initiators

Allı, Sema | Allı, Abdulkadir | Hazer, Baki

Article | 2012 | Journal of Applied Polymer Science124 ( 1 ) , pp.536 - 548

Macromonomer initiators behave as macro cross-linkers, macro initiators, and macromonomers to obtain branched and cross-linked block/graft copolymers. A series of new macromonomer initiators for atom transfer radical polymerization (MIM-ATRP) based on polyethylene glycol (M n = 495D, 2203D, and 4203D) (PEG) were synthesized by the reaction of the hydroxyl end of mono-methacryloyl polyethylene glycol with 2-bromo propanoyl chloride, leading to methacryloyl polyethylene glycol 2-bromo propanoyl ester. Poly (ethylene glycol) functionalized with methacrylate at one end was reacted with 2-bromopropionyl chloride to form a macromonomeric . . .initiator for ATRP. ATRP was found to be a more controllable polymerization method than conventional free radical polymerization in view of fewer cross-linked polymers and highly branched polymers produced from macromonomer initiators as well. In another scenario, ATRP of N-isopropylacrylamide (NIPAM) was initiated by MIM-ATRP to obtain PEG-b-PNIPAM branched block/graft copolymers. Thermal analysis, FTIR, 1H NMR, TEM, and SEM techniques were used in the characterization of the products. They had a thermo-responsive character and exhibited volume phase transition at â 36°C. A plasticizer effect of PEG in graft copolymers was also observed, indicating a lower glass transition temperature than that of pure PNIPAM. Homo and copolymerization kinetics were also evaluated. © 2011 Wiley Periodicals, Inc Daha fazlası Daha az

One-step synthesis of block-graft copolymers via simultaneous reversible-addition fragmentation chain transfer and ring-opening polymerization using a novel macroinitiator

Öztürk, Temel | Atalar, Mehmet Nuri | Göktaş, Melahat | Hazer, Baki

Article | 2013 | Journal of Polymer Science, Part A: Polymer Chemistry51 ( 12 ) , pp.2651 - 2659

One-step synthesis of block-graft copolymers by reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerization (ROP) by using a novel initiator was reported. Block-graft copolymers were synthesized in one-step by simultaneous RAFT polymerization of n-butylmethacrylate (nBMA) and ROP of ?-caprolacton (CL) in the presence of a novel macroinitiator (RAFT-ROP agent). For this purpose, first epichlorohydrin (EPCH) was polymerized by using H2SO4 via cationic ring-opening mechanism. And then a novel RAFT-ROP agent was synthesized by the reaction of potassium ethyl xanthogenate and polyepichlorohydrin (poly-EPCH). B . . .y using the RAFT-ROP agent, poly[CL-b-EPCH-b-CL-(g-nBMA)] block-graft copolymers were synthesized. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the one-step polymerization reaction were evaluated. The block lengths of the block-graft copolymers were calculated by using 1H-nuclear magnetic resonance (1H NMR) spectrum. The block length could be adjusted by varying the monomer and initiator concentrations. The characterization of the products was achieved using 1H NMR, Fourier-transform infrared spectroscopy, gel-permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, elemental analysis, and fractional precipitation (?) techniques. © 2013 Wiley Periodicals, Inc Daha fazlası Daha az

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