Reinvigorating Photo-Activated R-Alkoxysilanes Containing 2-Nitrobenzyl Protecting Groups as Stable Precursors for Photo-Driven Si–O Bond Formation in Polymerization and Surface Modification

This study aimed to revitalize silicon-based sol-gel chemistry methodologies utilizing photoprotected R-alkoxysilanes to control the synthesis of unique silicon-based materials. We have investigated the synthesis, characterization, light-induced deprotection, and subsequent polymerization/surface functionalization through the use of 2-nitrobenzyloxy-based photoremovable protecting groups (PPGs) as alkoxy reactive groups on ethyl and phenyl (R _<i>x</i> -(alkoxy) _<i>y</i> silanes, with <i>x</i> = 0-3 and <i>y</i> = 1-3). The photochemical dynamics, relative efficiencies, and kinetics of the novel alkoxysilane-based PPGs were thoroughly investigated using UV light irradiation by NMR and UV/vis methods. We then explored the tin-catalyzed coupling of photodeprotected products (R _<i>x</i> -silanols) to form polymers/oligomers. We have found that photoenabled removal of PPGs and conversion to silanols from all silane systems studied is achieved. Furthermore, these deprotected species are polymerizable into siloxanes and effectively used as light-controlled surface modifiers with masking techniques of which proof-of-concept examples are given, enabling promising application as photolithographic reagents.