Photochemical Sciences Ph.D. Dissertations

Synthesis, Characterization, and Application of Photocaged R-Alkoxysilanes and Siloxane Polymers

Date of Award

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Joseph Furgal (Committee Chair)

Second Advisor

Ellen Gorsevski (Other)

Third Advisor

Jayaraman Sivaguru (Committee Member)

Fourth Advisor

Alexander Tarnovsky (Committee Member)

Abstract

R-alkoxysilanes are the monomer workhorses of silicon-based sol-gel chemistry and are used as the building blocks for materials from silicas to silicones. However, since their inception, the sol-gel and siloxanes communities have struggled with uncontrolled hydrolysis, premature condensation, and overall polymerization and functionalization control. This dissertation focuses on the development of new silicon sol-gel chemistry methodologies which utilize photocaged R-alkoxysilanes and siloxane polymers to aid in synthetic control towards distinct silicon-based materials. We started our investigation with the synthesis and characterization of 2-nitrobenzyloxy photocage systems from ethyl and phenyl derivatives of Rx-(alkoxy)silanes, with x=0-3 and y=1-4, end group photocaged polydimethylsiloxanes, as well as photocaged polyhedral oligomeric silicon-based cage systems. Furthermore, we have also developed Rx-(alkoxy)silanes, with x=0-3 and y=1-4 that contain the 3-dimethylaminobenzyloxy photocage as a more stable alternative to the 2-nitrobenzyloxy based compounds. We have explored the photochemical responses for photo removal including kinetics, efficiency, stability, and tin catalyzed coupling of products to induce polymerization and surface functionalization. We have found that sufficient removal of the photocage groups was achieved, giving a new avenue to generate silicon-based materials. For this dissertation, Chapter 1 describes the background photochemical and silicon-based chemistries needed to understand these processes and their challenges. Chapter 2 details the extensive work on Rx-(alkoxy)silanes containing 2-nitrobenzyloxy groups and their performance in photochemical processes. Chapter 3 defines the work on 2-nitrobenzyloxy polymeric/oligomeric versions of silicon-based materials. Chapter 4 gives an overview of our preliminary work on 3-dimethylaminobenzyloxy photocaged Rx-(alkoxy)silanes. Finally, Chapter 5 gives conclusions and connections for this research to science and application.

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