Photochemical Sciences Ph.D. Dissertations

Development and Characterization of Photo-Initiated and Responsive Hybrid Organosilicon Materials

Date of Award

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Advisor

Joseph Furgal (Committee Chair)

Second Advisor

Pavel Anzenbacher (Committee Member)

Third Advisor

Alexey Zayak (Committee Member)

Fourth Advisor

Sri Kolla (Other)

Abstract

The development of hybrid organosilicon materials as both rapid curing coatings and photo-responsive sponges has been conducted utilizing silsesquioxane (SQ) based chemistries for the robustness they provide in the final materials. Additional research was conducted on the formation of sulfur-based SQ analogs. Chapter I will provide background about the synthesis of silsesquioxanes, their properties, and the favorability for three-dimensional material formation using these molecules. Additional information will include challenges and histories of siloxane based protective coatings and the use of both photo-radical and photo-acid-generating initiators in them, along with a brief explanation of photo-switches, specifically azobenzene and its derivatives and their use in sol-gels. Chapter II will discuss protective coatings for monuments and the specific needs associated with these materials. A history of the types of materials used and their faults will detail the desire for new materials aimed at this application. The development of a coating with three distinct curing methods (including photo-radical and photo-acid generating processes) which forms a protective layer with a mixture of partially formed polisilsesquioxane and oligosilsesquioxane structures as the backbone of the network. Findings and properties of the resulting coating formulations, modifiability, and alternative functionalities will be discussed in detail. Chapter III will discuss the use of photo-switches as crosslinkers in silicon-based networks. Previous work utilized Q-type silsesquioxanes (Q8M8H) and 4,4’-diallyloxyazobenzene (DAA) to develop photodynamic sponges. The modification process of these sponge materials, through both in-situ and post-polymerization functionalization, will be described. The effects on solvent preference resulting from the modifications will describe “sponge” uptake and swell-ability in various environmental pollutants. Chapter IV discusses the synthesis, characterization, and overall performance of an analog Q8M8H sponge system using 4,4’-divinylazobenzne (DVA), in place of 4,4’-diallyloxyazobenzene. Analysis of the resulting changes in swelling efficiency and solvent preference will be provided. Chapter V will describe the investigation into new species of organosilicon compounds. This chapter will detail early work on synthesizing novel silicon-sulfur silsesquioxane analogs, including the methods, challenges, and findings in this underdeveloped field. Chapter VI will provide an overview of the results, findings, and lessons learned through the research above.

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