Catalytic Systems for the Cross‐Linking of Organosilicon Polymers

Abstract

Silicones and silicone rubbers are omnipresent in household and industrial products such as lubricants,c oatings, sealants,i nsulators, medicald evices, etc. This plethora of applicationsa rises from their unparalleled properties including hydrophobicity,l ow surfacee nergy,c hemical inertness, extreme temperature stability,e lasticity,a nd biocompatibility.E vent hough silicones have been known for more than five decades, their chemistry is still far from fully understood. Industrially,t he vast majority of processesf or their synthesis, transformation, andu se are based on rather well established, alas outdated technologies, which are frequently empirical and poorly investigated. Thisr eview attempts to summarize the different approaches for the synthesis of silicone rubbers by vulcanizationorc uring of silicone polymers, the catalysts used, and the corresponding reaction mechanisms. Apart from the well-known methods (radical, hydrosilylation, and metal-based condensation), novel approaches such as organo-and bio-catalysis are also addressed.

Recent Advances in Rochow‐Müller Process Research: Driving to Molecular Catalysis and to A More Sustainable Silicone Industry

“…Before then, the only accessible process for the preparation of the required methylchlorosilanes was Kipping's organomagnesium procedure, which failed on the industrial scale owing to the challenges associated with the Grignard synthesis . On one hand, products were not selective and the components present in the final mixture were extremely difficult to separate . In addition, its commercialization was hampered by the lack of an industrially feasible procedure.…”

UV‐activated hydrosilylation of (Me‐Cp)Pt(Me)3: Enhanced photocatalytic activity, polymerization kinetics, and photolithography

“…Silicone polymers like silicone rubber and silicone resin have been widely used in various fields because of their outstanding properties. For better durability and reliability, they should be vulcanized to form a three‐dimensional crosslinked network via polycondensation at room temperature or hydrosilylation or peroxide reaction at high temperature . However, these curing methods have long been considered as a seriously time‐consuming and energy‐intensive process .…”

A new cross‐linked system of silicone rubber based on silicone‐polyurea block copolymer

“…Moreover, the following cross‐linked process was substantial important apart from the reinforcement. SR was generally cross‐linked to form network containing dangling chains by chemical reactions, such as silicon hydrogen addition reaction and free radical reaction . An unavoidable problem was that the poisoning and residue of the catalyst could affect the oxidation resistance and thermal stability of SR …”

“…Up to now, a variety of efforts had been done via different surface treatments to improve the interfacial compatibility, such as grafting of polymeric oligomers to the surface of nanofillers, the treatment with reactive modifications, and subsequent reactions (eg, esterification) on the surface. 5,6 Obviously, it is a laborious and key process that had great influence on SR. Moreover, the following cross-linked process was substantial important apart from the reinforcement.…”

“…SR was generally cross-linked to form network containing dangling chains by chemical reactions, such as silicon hydrogen addition reaction and free radical reaction. 5,6 An unavoidable problem was that the poisoning and residue of the catalyst could affect the oxidation resistance and thermal stability of SR. 7 Recently, progress in supramolecular chemistry provided a new approach to avoid the above key problems. The units capable of formation of hydrogen bonding, such as urethane, amides, and imides, [8][9][10][11] were introduced to -Si-O-Sichains.…”