Design, synthesis and polymerization of highly branched pseudodendrimers through tandem reactions and kinetics measurements of pseudodendrimeric polymerization

dc.contributor.advisorJohnson, Dave M.
dc.contributor.authorWang, Junyan
dc.contributor.committeeMemberHan, Hyunsoo
dc.contributor.committeeMemberTiekink, Edward R. T.
dc.contributor.committeeMemberZhao, Cong-Gui
dc.date.accessioned2024-03-08T17:34:22Z
dc.date.available2024-03-08T17:34:22Z
dc.date.issued2008
dc.descriptionThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.
dc.description.abstractDendritic polymers exhibit some unique properties which clearly distinguish them from other polymers. Their fascinating structural features have made them one of the best candidates for nanotechnology applications. The synthesis of dendrimers involves multi-step procedures including protective group technology. This results in high cost and accessibility only in small quantities. Hyperbranched polymers can be prepared in one-pot polymerization of ABn monomers, however, a competitive reaction between the formations of linear chains and branching occurs, and consequently the structure is imperfect and the control over layers or generations vanishes. Pseudodendrimers are intermediate polymers between hyperbranched polymers and dendrimers. Similar to dendrimers, they are also fully branched structures. But they are not perfectly symmetric, like hyperbranched polymers. Pseudodendrimers may serve as potential replacements for dendrimers. We have developed a single-reaction synthesis of pseudodendrimers. The overall goals of this project are to optimize the synthesis of pseudodendrimers, measure the kinetics of pseudodendrimer polymerization, show that pseudodendrimers have similar properties to dendrimers. The careful design of an ABB' monomer leads to higher branching by virtue of a tandem reaction that increases the reactivity of linear units during polymerization. Our work has shown that 6-amino-3-bromophthalide leads to a highly branched polymer via bromohydrin decomposition during polymerization, giving polymers of Mn of 3000 and a polydispersity index of 1.03. Our findings indicate a degree of branching of 0.84, suggesting the polymerization is a single-reaction synthesis of a pseudodendrimer. Polymerization of analogous polymers confirms our proposed intermediate. The kinetics of the model reactions show that the reaction is first order in benzylamine. We determined that the energy of activation (E a) for the first addition reaction is 8.9 kcal mol-1 and Ea for the second addition reaction is 6.6 kcal mol-1. These data imply that dimer formation step is the rate limiting step of the two-to-one addition reaction. The reaction rate of linear units (product are dendritic units), kt, is about 30 times faster than the reaction rate of terminal units (product are linear units), kd. These differences of reactivity satisfy our designed requirements for the 3-bromophthalide-based ABB' monomer, will lead to enhanced DB, and consequently form pseudodendrimers on polymerization.
dc.description.departmentChemistry
dc.format.extent204 pages
dc.format.mimetypeapplication/pdf
dc.identifier.isbn9780549917960
dc.identifier.urihttps://hdl.handle.net/20.500.12588/6045
dc.languageen
dc.subjectEnhanced Degree of Branching
dc.subjectHyperbranched Polymer
dc.subjectPseudodendrimer
dc.subjectPseudodendrimeric Kinetics
dc.subjectTandem Reactivity
dc.subject.classificationPolymer chemistry
dc.subject.classificationOrganic chemistry
dc.subject.lcshDendrimers
dc.subject.lcshPolymerization
dc.subject.lcshNanotechnology
dc.titleDesign, synthesis and polymerization of highly branched pseudodendrimers through tandem reactions and kinetics measurements of pseudodendrimeric polymerization
dc.typeThesis
dc.type.dcmiText
dcterms.accessRightspq_closed
thesis.degree.departmentChemistry
thesis.degree.grantorUniversity of Texas at San Antonio
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy

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