Rosen, Brad Matthew

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  • Publication
    Advances in Supramolecular and Macromolecular Chemistry Through the Development of New Synthetic Methodologies
    (2009-11-17) Rosen, Brad Matthew
    Development of complex supramolecular and macromolecular systems is driven by the development of new enabling synthetic methodologies. The demands placed upon specific chemical transformations are amplified for dendritic systems prepared via iterative synthesis. Three synthetic methods, Ni-catalyzed neopentylglycolborylation, Single-Electron Transfer Living Radical Polymerization, and “Thio-Bromo Click” Chemistry are elaborated and utilized in the synthesis of new covalent and supramolecular dendrimers and dendritic macromolecules. Sequential nickel catalyzed neopentylglycolborylation and cross-coupling of aryl halides is pioneered and harnessed as a tool for the synthesis of a new class of self-assembling dendron, biphenylpropyl ether dendrons. Through the synthesis of generational libraries of biphenylpropyl ether dendrons, new modes of self-assembly are discovered, including the first example of self-organizable vesicular spheres, which represent the largest reported spherical supramolecular dendrimers with MW of 1.7 x 106 g/mol. More importantly, comparison of all libraries of self-assembling dendrons with that of the biphenylpropyl ether dendrons, reveal predictability in their self-assembly and allow for the construction of a ‘nano-periodic’ table of dendrons. This predictability, while useful for rational design of new self-assembled systems, limits the likelihood of discovering new modes of self-assembly via library synthesis using existing design strategies. A new design strategy, the “Deconstruction Approach”, where a dendritic topology is systematically stripped of its branches, is developed and applied to biphenylpropyl ether dendrons. This first library of “Deconstructed” biphenylpropyl ether dendrons demonstrates the power of the strategy to uncover a multitude of new architectures hidden in previously unexplored dendron topologies. In addition to self-assembling dendrons, dendritic macromolecules possess their own unique synthetic challenges derived from the merging of organic iterative synthesis and polymerization. The mechanism of a new robust polymerization technique, Single-Electron Transfer Living Radical Polymerization (SET-LRP) is elaborated. “Thio-Bromo Click” chemistry is developed as a new tool for the construction of poly(thio-propionoate (PTP) dendrimers. Through the combination of SET-LRP “Thio-Bromo Click” chemistry, an expeditious three-step “Branch and Grow” strategy for the synthesis of dendritic macromolecules is possible.