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Browsing by Author "Ashby, Richard D."

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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.
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    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.