Photo-click Chemistry

: Fabrication of Photo-thermoresponsive Materials for Advanced Applications

Abstract

This thesis explores two interconnected projects aimed at advancing soft materials through the application of the light-induced strain-promoted alkyne-azide cycloaddition (hvSPAAC) to enhance the materials’ physical and chemical properties. The hvSPAAC reaction involves the photo-unmasking of cyclopropenone-masked dibenzocyclooctyne (hvDIBO) groups with 365 nm light to produce strained alkynes that cyclize with azides to form triazoles.
The first project discusses the development of a photo-strengthening hydrogel system that leverages the hvSPAAC reaction for spatio-temporal crosslinking of the hydrogel. This reaction provides rapid and highly selective control over crosslinking density, significantly enhancing the material's viscoelasticity and allowing for the design of spatio-temporal patterns of mechanical properties. Although different chemistries for the spatio-temporal localization of molecules and gradients of chemical signals within soft materials are available, the achievement of spatio-temporal patterns of mechanical properties and their characterization remain considerable challenges. Herein, the photo-strengthening hydrogel system was demonstrated by fabricating a bilayered actuator with UV-induced bending and by encoding mechanical information for digital information storage. Microindentation analysis was essential for the characterization of the soft material system. This methodology opens a route to the fabrication of soft materials with patterned mechanical properties and addresses important emerging challenges not only in soft robotics and information storage, but also in tissue engineering and biotechnology.
The second project in this work explores how photo-click chemistry can contribute to the design and bottom-up synthesis of photo-thermoresponsive gold colloidosome protocells—self-assembled micro-compartmentalized systems mimicking living cells—endowed with advanced chemically programmed, bio-inspired functions. Colloidosomes offer advantages over other protocell models due to their robust and tuneable physical-chemical properties. Significant progress was made by synthesizing polymer-coated gold nanoparticles (AuNPs) that form functional colloidosomes. These colloidosomes show promise for photothermal applications and can modulate their permeability and mechanical properties with UV light. The aim of this work is to establish a foundation for creating inorganic protocellular materials (PCMs).
In summary, this thesis highlights advancements in hydrogels with photo-click chemistry and the development of photo-thermoresponsive gold colloidosomes. The research demonstrates the effectiveness of microindentation in soft material characterization and opens new possibilities for applications in soft robotics, biomimetic chemistry, and information storage.

Date of Award	10 Dec 2024
Original language	English
Awarding Institution	University of Bristol
Sponsors	University of Western Ontario
Supervisor	Sebastien Rochat (Supervisor), Mark Workentin (Supervisor) & Pierangelo Gobbo (Supervisor)