Metastable-state Photoacids and the Related Photo-Responsive Polymers
Metastable-state photoacid is a type of photo-sensitive compounds that can release large amount of protons reversibly upon visible-light irradiation. Since being developed by our group in 2011, metastable-state photoacid has been utilized to develop many applications that involve controlling proton transfer processes. Since proton transfer process is one of the most common processes in nature, metastable-state photoacid is a powerful tool to control various processes with light. A introduction of metastable state photoacid is described in Chapter 1. In Chapter 2, metastable-state photoacids with different substituents were designed to study the relationship between their structures and physicochemical properties. In Chapter 3, a novel fragrant releasing material was developed. Fragrant molecules were linked onto a polymer by acid-sensitive covalent bonds. In the presence of a metastable-state photoacid, release of the fragrant molecules could be activated by visible light and stopped by turning off the light. This fast switching of release was achieved by a new metastable-state photoacid with fast reverse reaction. In Chapter 4, a polymer nanoparticle which can be dissolved in the solution upon visible light irradiation was developed. The nanomaterial was constructed by ionic bond crosslinking between an acrylic acid polymer and polyvinylpyridine. Reversible dissolution and reformation of the polymer nanoparticle was achieved by protonation and deprotonation of the crosslinker with a metastable-state photoacid under light and in the dark respectively. In Chapter 5, a polymer film whose mechanical strength changed under visible light was developed. The visible light irradiation could either weaken or strengthen the mechanical strength of the polymer film depending on whether an external force was applied to the material when it was irradiated. In Chapter 6, novel photobases were designed by similar strategies as metastable-state photoacids. Photobase PB7 showed promising photobasicity, which will guide us to develop photobase with better performance.