New Chemical Tools for the Design of Stimuli-Responsive Supramolecular Assemblies and Functional Polymers

Stimuli-responsive functional polymers and supramolecular assemblies are widely used in materials science and bio-applications, such as self-healing materials, drug delivery, tissue engineering, and controlled catalysis. Covalent and noncovalent bond interactions play essential roles on the stimuli-responsiveness. Fundamental studies on the molecular bases and principles behind these interactions are crucial for manipulating corresponding responsiveness and designing materials with optimal properties. In this dissertation, new chemical tools are introduced to investigate both the covalent and noncovalent alterations, and their impacts on supramolecular assemblies and functional polymers. In the first half of this dissertation, the monomer and excimer fluorescence of 7-diethylaminocoumarin has been utilized to investigate the dynamics of amphiphiles in temperature-responsive assemblies and protein concentration dependent supramolecular dissociations. Noncovalent alterations from temperature changes and protein binding were reflected in the variations of monomer and excimer fluorescence signals. Structure-property correlations uncovered the mechanisms and principles to manipulate corresponding responses. In the second half of this dissertation, new chemistries based on covalent bond alterations have been developed to design functional polymers and assemblies. The “HAM” reaction developed in the dissertation is the first multicomponent reaction exhibiting thermally activated dynamic covalent chemistry behaviors. The chemical joint generated could either be dynamic or degradable in response to different chemical environments. The binding of spiropyran and phenylboronic acid has been explored to trigger the ring-opening isomerization of spiropryan, which potentially generates delocalized lipophilic cations and exhibits ROS responsive dissociation. This chemical transformation has been attempted for the potential application in mitochondria targeting