Synthesis and applications of core functional hyperbranched polyglycerol

Zill, Andrew T.

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Description

Title

Synthesis and applications of core functional hyperbranched polyglycerol

Author(s)

Zill, Andrew T.

Issue Date

2011-08-26T15:34:16Z

Director of Research (if dissertation) or Advisor (if thesis)

Zimmerman, Steven C.

Doctoral Committee Chair(s)

Zimmerman, Steven C.

Committee Member(s)

• Braun, Paul V.
• White, M. Christina
• Kong, Hyun Joon

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Hyperbranched polyglycerol
• Photobleaching
• Click chemistry
• Molecular imprinting
• Metathesis
• Antifading Agents
• Fluorescence

Abstract

This dissertation details the synthesis of a new alkyne core functional hyperbranched polyglycerol and describes their use as potential monomolecular imprinting materials and increasing the photostability of fluorescent dyes. The first chapter describes two methods for the synthesis of the polymers and its formal [3+2] cycloaddition with organic azides in the presence of copper, commonly referred to as click chemistry. The two methods allow preparation of low molecular weight polymers, MW < 10,000 g/mol and high MW > 100,000 g/mol. The polymers and their derivatives are characterized by a variety of analytical techniques to establish the size, degree of branching, and initiator incorporation for both the low and high molecular weight material. A method for decreasing polydispersity, a common issue for hyperbranched polymers, is also described. This chapter includes two applications for these new polymers including attachment to the surface of a gold nanoparticle, and the synthesis of an acid sensitive unimolecular micelle. In the first application, the alkyne core is converted to an amine which allows the polymer to act as a ligand on the gold surface. Despite the presence of the amine, the particle’s remain neutral (zeta potential = -0.01) and are stable to salt induced precipitation. In the second application unimolecular micelles were tested for biocompatibility, and their ability to encapsulate and release a hydrophobic guest molecule. The second chapter describes the synthesis of branched star polymers or pseudodendrimers using an adenosine core in an effort to synthesize a water soluble organic nanoparticle capable of recognizing nucleic acid residues. A general route to highly cross-linked water soluble nanoparticles is presented which uses metathesis cross-linking and osmium catalyzed dihydroxylation. The nanoparticles could be hydrolyzed to remove the adenosine template. However, qualitative tests using equilibrium dialysis showed very low, nonspecific binding to nucleoside guests. The end of the chapter further studies the cross-linking process, and shows how the polymers stiffness changes with increasing cross-link density using 1H NMR T1 relaxation times. The third chapter describes two methods for the use of polyglycerol to increase the photostability of organic dyes. The first method uses the steric bulk of polyglycerol as a protective layer to prevent interaction of the dye with molecular oxygen or to increase the water solubility of stable but insoluble dyes. Polyglycerol modified with fluorescein at the core was shown to be up to 3 times more stable than free fluorescein in solution. The polymer conjugates were also less affected by iodide quenching. In both tests there was no difference between cross-linked and uncross-linked polymer. Polyglycerol was also used to alter the water solubility of the insoluble but stable perylene diimide dye. The second method uses polyglycerol not as a steric barrier, but as a scaffold to covalently link fluorescent dyes to antifading agents. The results show that the co-localization of the dye and antifading agents due to the covalent attachment to the polymer scaffold reduces photobleaching similarly to that observed for antifading agents in solution.

Graduation Semester

2011-08

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Copyright and License Information

Copyright 2011 Andrew T. Zill

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