Depolymerization protocol for linear, branched, and crosslinked end-of-life silicones with boron trifluoride diethyl etherate as the depolymerization reagent

A robust depolymerization route for polysiloxanes

A versatile, robust, and stable tetrabutylammonium difluorotriphenylsilicate (TBAT) catalyst has been deployed for efficient depolymerization of silicones. This catalyst is soluble in a variety of organic solvents and is stable up to 170 °C, enabling a wide range of reaction conditions under which F--catalysed siloxane bond cleavage can be initiated. This effort offers significant advancement overcoming the traditional limitations of silicone depolymerization, such as high catalyst loading, storage and handling, and few viable reaction media.

Chemical Recycling of High-Molecular-Weight Organosilicon Compounds in Supercritical Fluids

The main known patterns of thermal and/or catalytic destruction of high-molecular-weight organosilicon compounds are considered from the viewpoint of the prospects for processing their wastes. The advantages of using supercritical fluids in plastic recycling are outlined. They are related to a high diffusion rate, efficient extraction of degradation products, the dependence of solvent properties on pressure and temperature, etc. A promising area for further research is described concerning the application of supercritical fluids for processing the wastes of organosilicon macromolecular compounds.

Synthesis and Reactivity of the First Isolated Hydrogen-Bridged Silanol-Silanolate Anions

We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization.

Facile Approach to Recycling Highly Cross-Linked Thermoset Silicone Resins under Ambient Conditions

Silicone resins are traditional thermoset polymers with an inorganic backbone, affording chemical inertness and high thermal stability, which also makes them inherently difficult to recycle by traditional methods. Here, we demonstrate that catalytic amounts of fluoride ion at room temperature solubilize highly cross-linked silicone resins initially cured up to 250 °C. After solubilization equilibria are achieved, solvent is removed to reform the polymer network. Coatings on aluminum substrates and monoliths of virgin and recycled silicone resins were evaluated for hydrophobicity, wear resistance, substrate adhesion, and thermal stability. Silicones recycled under optimized conditions retained nearly 100% wear resistance, thermal stability, and adhesion properties. In some instances, the recycled coatings offer properties superior to the initial materials.