Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Chemistry
Supervisor
Workentin, Mark S.
2nd Supervisor
Rochat, Sebastien
Affiliation
The University of Bristol, UK
Co-Supervisor
3rd Supervisor
Gobbo, Pierangelo
Affiliation
University of Trieste, ITA
Co-Supervisor
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.
Summary for Lay Audience
This thesis looks at two related projects aimed at improving the physical and chemical properties of synthetic, soft materials using a chemical reaction triggered by light. This reaction also provides the user with increased control over the materials’ chemical structure based on the amount and duration of light used as a stimulus.
The first project focuses on making hydrogels (gel-like materials) that can physically strengthen by applying the light-sensitive reaction. This reaction helps to easily create intricate patterns of strengthened areas in hydrogels and to adjust the material’s properties with high precision. For example, by changing the properties of a bilayered hydrogel with UV light, reproducible motion of the material can be remotely induced. The light-triggered chemical reaction also allows the user to store mechanical information into soft materials. The stored information can then be extracted from the material with a specialized machine, called a microindenter, that analyzes the stiffness differences across the material’s surface. The large quantity of data collected by the microindenter can then be processed with a custom software developed by our research group to quickly and easily obtain maps of the material’s mechanical properties. This new technique can be useful for applications in creating soft robots, storing digital information, and even creating artificial tissues.
The second project is about creating tiny, cell-like structures using gold nanoparticles. Gold nanoparticles were chosen as the building blocks for these artificial cell mimics because of their known photothermal (using light to generate heat) properties. These cell mimics, called colloidosomes, can be designed to change their physical properties in response to light irradiation, as this triggers a temperature increase around the material and a subsequent alteration in its temperature-responsive structure. The same light-triggered chemical reaction from the previous project can also be applied to this system to further enhance the colloidosomes for various applications. These metal-based colloidosomes have potential uses in photothermal applications and can be adjusted to mimic the functions of biological cells. Overall, this thesis shows how light-sensitive chemistry can enhance soft materials and create advanced, cell-like structures with new functionalities and applications.
Recommended Citation
Park, Jun Hyeong, "Photo-click Chemistry: Fabrication of Photo-thermoresponsive Materials for Advanced Applications" (2024). Electronic Thesis and Dissertation Repository. 10541.
https://ir.lib.uwo.ca/etd/10541
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