Date of Thesis

8-13-2015

Thesis Type

Masters Thesis (Bucknell Access Only)

Degree Type

Master of Science

First Advisor

Eric Tillman

Abstract

Recent interest in cyclic polymers has been motivated by potential advantages of these architectures for application in drug delivery vehicles and artificial photosynthesis. Polymers formed by reversible deactivation radical polymerization (RDRP) with a variety of vinyl monomers can produce controlled, monomodal dispersity samples with post polymerization functionality. The main focus of this work deals with atom transfer radical polymerization (ATRP) and radical trap assisted atom transfer radical coupling (RTA-ATRC) to synthesize cyclic polymers by a unimolecular homodifunctional approach to ring closure. Cyclic and dicyclic poly(methyl methacrylate) (PMMA) were prepared by nitrosobenzene (Nbz) RTA-ATRC under high dilution and pseudo-high dilute conditions with N,N,N¿,N¿¿,N¿¿-pentamethyldiethylenetriamine (PMDETA) ligand. Cyclic poly(methyl acrylate) (PMA) and cyclic diblock poly(methyl acrylate)-block-polystyrene (PMA-b-PS) were synthesized by 2-methyl-2-nitrosopropane (MNP) RTA-ATRC also by the same method to favor intramolecular coupling with the variation of tris[2-(dimethylamino)ethyl]amine (Me6TREN) ligand to optimize cyclization. Initial characterization was based on hydrodynamic volume shifts of linear to cyclic species in gel permeation chromatography (GPC) elution times. Characterization of both linear and cyclic analogs was also done by ESI MS and DSC. Thermolysis of the C-O bond in the alkoxyamine caused reversion back to linear polymers, as observed by GPC, providing further evidence of the cyclic formation and the proposed mechanism. Separate bimolecular homodifunctional approaches for cyclization of PMMA are introduced, with cyclization by RTA-ATRC or copper assisted azide-alkyne cycloaddition (CuAAC) being the ultimate goal. Orthogonality of CuAAC and ATRC was also studied using low coupling temperatures and C-Cl terminated polymers. Lastly, stereoregularity of copolymers formed by RDRP, composed of alternating electron deficient and electron rich styrenic monomers, was partially induced by pi-pi stacking, as confirmed by 13C NMR.

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