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Synthesis of PMMA-PTHF-PMMA and PMMA-PTHF-PST linear and star block copolymers

Macit, Hülya | Hazer, Baki

Article | 2004 | Journal of Applied Polymer Science93 ( 1 ) , pp.219 - 226

Combination of cationic, redox free radical, and thermal free radical polymerizations was performed to obtain linear and star polytetramethylene oxide (poly-THF)-polymethyl methacrylate (PMMA)/polystyrene (PSt) multiblock copolymers. Cationic polymerization of THF was initiated by the mixture of AgSbF6 and bis(4,4' bromo-methyl benzoyl) peroxide (BBP) or bis (3,5,3',5' dibromom-ethyl benzoyl) peroxide (BDBP) at 20°C to obtain linear and star poly-THF initiators with MW varying from 7,500 to 59,000 Da. Poly-THF samples with hydroxyl ends were used in the methyl methacrylate (MMA) polymerization in the presence of Ce(IV) salt at 40°C . . .to obtain poly(THF-b-MMA) block copolymers containing the peroxide group in the middle. Poly(MMA-b-THF) linear and star block copolymers having the peroxide group in the chain were used in the polymerization of methyl methacrylate (MMA) and styrene (St) at 80°C to obtain PMMA-b-PTHF-b-PMMA and PMMA-b-PTHF-PSt linear and star multiblock copolymers. Polymers obtained were characterizated by GPC, FT-IR, DSC, TGA, 1H-NMR, and 13C-NMR techniques and the fractional precipitation method. © 2004 Wiley Periodicals, Inc Daha fazlası Daha az

Synthesis and characterization of diblock, triblock, and multiblock copolymers containing Poly(3-hydroxy butyrate) units

Arslan, Hülya | Menteş, Ayfer | Hazer, Baki

Article | 2004 | Journal of Applied Polymer Science94 ( 4 ) , pp.1789 - 1796

A poly[(R,S)-3-hydroxybutyrate] macroinitiator (PHB-MI) was obtained through the condensation reaction of poly[(R,S)-3-hydroxybutyrate] (PHB) oligomers containing dihydroxyl end functionalities with 4,4'-azobis(4-cyanopentanoyl chloride). The PHB-MI obtained in this way had hydroxyl groups at two end of the polymer chain and an internal azo group. The synthesis of ABA-type PHB-b-PMMA block copolymers [where A is poly(methyl methacrylate) (PMMA) and B is PHB] via PHB-MI was accomplished in two steps. First, multiblock active copolymers with azo groups (PMMA-PHB-MI) were prepared through the redox free-radical polymerization of methyl . . . methacrylate (MMA) with a PHB-MI/Ce(IV) redox system in aqueous nitric acid at 40°C. Second, PMMA-PHB-MI was used in the thermal polymerization of MMA at 60°C to obtain PHB-b-PMMA. When styrene (S) was used instead of MMA in the second step, ABCBA-type PMMA-b-PHB-b-PS multiblock copolymers [where C is polystyrene (PS)] were obtained. In addition, the direct thermal polymerization of the monomers (MMA or S) via PHB-MI provided AB-type diblocks copolymers with MMA and BCB-type triblock copolymers with S. The macroinitiators and block copolymers were characterized with ultraviolet-visible spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, cryoscopic measurements, and thermogravimetric analysis. The increases in the intrinsic viscosity and fractional precipitation confirmed that a block copolymer had been obtained. © 2004 Wiley Periodicals, Inc Daha fazlası Daha az

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