Doctoral Degrees (Chemistry and Polymer Science)

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Browsing Doctoral Degrees (Chemistry and Polymer Science) by Author "Alkaabi, Khalifa"

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    The synthesis, chemical and physical characterisation of selected energetic binder systems
    (Stellenbosch : University of Stellenbosch, 2009-03) Alkaabi, Khalifa; Van Reenen, Albert; University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science.
    Due to numerous accidents involving munitions, recent interest has focused on the development and use of insensitive munitions (IM). Polymeric materials are used in insensitive munitions as binders or plasticizers. Most of the polymeric binders used are based on polycondensation reaction via using urethane linkages. The main aim of this study was the synthesis and characterization of selected energetic thermoplastic elastomers binder based on utilizing controlled free radical polymerization. This was achieved by using hydroxyl terminated poly (epichlorohydrin) (PECH-diol) and hydroxyl terminated glycidyl azide polymer (GAP-diol) as starting materials, and the subsequent synthesis of different macroinitiators. These macro-initiators were used to polymerize methyl methacrylate (MMA) to obtain thermoplastic elastomers. PECH-diol was prepared by cationic ring-opening polymerization (CROP) based on using borontrifluoride etherate (BF3-etherate) as catalyst and a low molecular weight diol as initiator. GAP-diol was synthesized by the reaction of PECH-diol with sodium azide in organic solvent.. Poly(epichlorohydrin-methyl methacrylate) (PECH-PMMA) and poly(glycidyl azidemethyl methacrylate) (GAP-PMMA) block copolymers were prepared by free radical polymerization of MMA monomer in presence of PECH and GAP macro-azoinitiator (MAI). The MAIs were prepared by the polycondensation reaction of hydroxyl terminated groups of elastomer with 4,4' azobis (4-cyanopentanoyl chloride) (ACPC). The phase behavior of blends of amorphous PMMA/PECH-diol and PMMA/GAP-diol was also investigated. Poly(epichlorohydrin-methyl methacrylate) (PECH-PMMA) and poly(glycidyl azidemethyl methacrylate) (GAP-PMMA) graft copolymers were synthesized by photopolymerization of MMA in presence of PECH and GAP with pendant N,Ndiethyldithiocarbamate groups as macro-photoiniferters. . Photopolymerization of MMA proceeded in a controlled fashion. A macro RAFT agent, based on the reaction of PECH with pendent dithiobenzoate was prepared. The macro-RAFT agent was used in the controlled thermal bulk polymerization of methyl methacrylate. Finally, living/controlled radical polymerization of MMA with four different photoiniferters, namely benzyl diethyl dithiocarbamate (BDC), 2-(N,N-diethyldithiocarbamyl) propionic acid (PDC), 2-(N,Ndiethyldithiocarbamyl) isobutyric acid (DTCA), and diethyl dithiocarbamateepichlorohydrin was achieved.