Silane diamine copolymers: efficient synthesis, solvent absorption capacity, and limitations as coatings

Abstract

Although silane diamine copolymers have captured the attention of the catalysis community, the optimization of their synthesis and end uses have yet to be explored. In this study, a well-defined Earth-abundant metal catalyst, [(^2,6-iPr₂PhBDI)Mn(μ-H)]₂, has been found to couple organosilanes to diamines to prepare networks that feature varied silane substitution and diamine chain lengths. By performing dehydrocoupling in the absence of solvent with 0.01 mol% catalyst loading, substrate utilisation turnover frequencies of up to 300 s⁻¹ have been achieved at early reaction times, the highest Si–N dehydrocoupling activity to be observed on a per catalyst basis. These networks have been employed as absorbents for common organic solvents, a property that had not been studied for this class of materials. By incorporating a long-chain hydrophobic linker, one network has been found to absorb 7.7× its original mass in THF and recycling has been demonstrated upon solvent removal. Controlling the degree of dehydrocoupling also offered an opportunity to deposit coatings from freshly-prepared silane diamine polymer solutions and monitor their integrity upon curing in air. While uniform and persistent coatings have been obtained from 1,6-diaminohexane derived polymers, the need to prepare dilute solutions that have a short shelf-life and the tackiness associated with extended dry times have been identified as potential limitations.