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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Synthesis of Arborescent Amphiphilic Copolymers

Alzahrany, Yahya 01 January 2013 (has links)
Living anionic polymerization techniques were applied to the synthesis of arborescent (dendritic) well-defined graft polymers having core-shell morphologies, with a hydrophobic core and a hydrophilic shell. Cycles of polystyrene substrate acetylation and anionic grafting yielded successive generations of arborescent polystyrenes. The anionic polymerization of styrene with sec-butyllithium provided polystyryllithium serving as side chains. These were coupled with a linear acetylated polystyrene substrate to obtain a generation zero (G0) arborescent polymer. An analogous G0 hydroxyl-functionalized polystyrene substrate with hydroxyl end groups was also obtained by a variation of the same technique, using a bifunctional organolithium initiator containing a hydroxyl functionality protected by a silyl ether group to generate the polystyrene side chains. These were coupled with the linear acetylated polystyrene substrate and subjected to a deprotection reaction to give the G0 polymer functionalized with hydroxyl groups at the chain ends. A similar procedure was used to generate a hydroxyl-functionalized arborescent G1 polymer from the corresponding G0 acetylated polystyrene substrate. The growth of polyglycidol chain segments was attempted from the hydroxyl-functionalized cores, to form a hydrophilic shell around the hydrophobic cores, but led to extensive degradation. A click reaction was also developed to synthesize the amphiphilic copolymers and was much more successful. In this case alkyne-functionalized arborescent polystyrene substrates, obtained by a modification of the hydroxyl-functionalized arborescent polystyrenes, were coupled with azide-functionalized polyglycidol side chains.
2

Synthesis of Arborescent Amphiphilic Copolymers

Alzahrany, Yahya 01 January 2013 (has links)
Living anionic polymerization techniques were applied to the synthesis of arborescent (dendritic) well-defined graft polymers having core-shell morphologies, with a hydrophobic core and a hydrophilic shell. Cycles of polystyrene substrate acetylation and anionic grafting yielded successive generations of arborescent polystyrenes. The anionic polymerization of styrene with sec-butyllithium provided polystyryllithium serving as side chains. These were coupled with a linear acetylated polystyrene substrate to obtain a generation zero (G0) arborescent polymer. An analogous G0 hydroxyl-functionalized polystyrene substrate with hydroxyl end groups was also obtained by a variation of the same technique, using a bifunctional organolithium initiator containing a hydroxyl functionality protected by a silyl ether group to generate the polystyrene side chains. These were coupled with the linear acetylated polystyrene substrate and subjected to a deprotection reaction to give the G0 polymer functionalized with hydroxyl groups at the chain ends. A similar procedure was used to generate a hydroxyl-functionalized arborescent G1 polymer from the corresponding G0 acetylated polystyrene substrate. The growth of polyglycidol chain segments was attempted from the hydroxyl-functionalized cores, to form a hydrophilic shell around the hydrophobic cores, but led to extensive degradation. A click reaction was also developed to synthesize the amphiphilic copolymers and was much more successful. In this case alkyne-functionalized arborescent polystyrene substrates, obtained by a modification of the hydroxyl-functionalized arborescent polystyrenes, were coupled with azide-functionalized polyglycidol side chains.

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