Synthesis, Characterization, and Thermal Properties of Fluoropyridyl-Functionalized Siloxanes of Diverse Polymeric Architectures
Kevin A. Stewart, Dylan Shuster, Maria Leising, Isaac Coolidge, Erica Lee, Charles Stevens, Andrew J. Peloquin, Daniel A. Kure, Abby R. Jennings, Scott T. Iacono
Abstract
High-temperature linear fluoropyridyl silicone-based oils and network elastomers were prepared via hydrosilylation with multifunctional perfluoropyridine (PFP)-based monomers possessing terminally reactive alkenes. Monomers with varying degrees of functionalization were prepared in a scalable manner and in high purity via the facile, regio-selective, nucleophilic aromatic substitution (SNAr) of PFP in good isolated yields. These multi-reactive monomers were polymerized via Pt-catalyzed hydrosilylation with hydride-terminated polydimethylsiloxanes (H-PDMSs) possessing varying degrees of polymerization and cross-linked with the highly functionalized octadimethylhydrosilyl cubic siloxane. These resulting polymers of varying architecture possessed exceptional thermal stability with no onset of degradation up to 430 °C and char yields as high as 62%, under inert pyrolysis conditions when modified with cubic siloxane. Furthermore, by nature of the aliphatic or aromatic content, programmable glass transition temperatures were achieved from these elastomeric materials. Finally, the linear 3,5,6-fluoropyridine PDMS systems demonstrated the ability to undergo regio-controlled post-functionalization via SNAr with 4-bromophenol, allowing access to silicone oils with potentially tailorable properties for desired applications.