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Sequence-Controlled Polymerization Through a Metal-Free Multicomponent Click Reaction
Abstract
Multicomponent reactions have been utilized to access unique molecular architectures while simultaneously being atom and step economical. This strategy has been employed in developing sequence-controlled polymers but is seldom used for conjugated polymers. Controlling the sequence of conjugated polymers can allow for the fine tuning of their optical and electronic properties. The work reported herein is the development of a multicomponent polymerization (MCP) utilizing nitrile oxide alkyne cycloaddition (NOAC) in tandem with imine condensation. A model system was first developed to optimize the conditions of the cascade with simple molecules including a primary nitroalkane, aldehyde, isocyanate, and alkyne prior to its implementation into an MCP. A sterically hindered tertiary base was found to be necessary to promote the desired NOAC reaction while an additive such as a Lewis acid or cyclic secondary amine was found to facilitate the imine condensation. Conditions promoting the reaction cascade were identified and optimized to deliver the final product of the model system in 38% yield. While these conditions were less efficient with other substrates, an exploration of the substrate scope was initiated. Finally, using these conditions in a polymerization generated oligomeric materials with a low molar mass (1.8 kg/mol) and the complexity of the spectroscopical data has thus far prevented the full characterization of the synthesized macromolecules. This study sets the stage for an attractive strategy to synthesize a unique class of conjugated polymers containing isoxazole and imine linkages and to investigate the relationship between the sequence of repeating subunits and the optical and electronic properties of the polymer.
Subject
Sequence-Controlled PolymerConjugated Polymer
Multicomponent Reaction
Multicomponent Polymerization
Click Chemistry
Atom Economy
Step Economy
Citation
Holter, Alexander R (2022). Sequence-Controlled Polymerization Through a Metal-Free Multicomponent Click Reaction. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198474.