Reactivity of Polysilazanes Allows Catalyst‐Free Curing of Silicones

Abstract

Silicones are typically cured at room temperature by means of metal catalyst such as tin or platinum. When networks are formed, the catalyst becomes unrecoverable, which is of economic as well as environmental concern. Very few methods for producing metal catalyst-free room-temperature-vulcanized (RTV) silicones exist and require conditions unavailable in industrial settings. Through the study of organic polysilazane (PSz) reactivity with simple alcohols by nuclear magnetic resonance, an unexpected fragmentation preference is discovered for breaking the Si-N bond rather than the Si-H; thereby, casting a new light on the fragmentation mechanism of PSzs. Utilizing the PSz fragmentation as a silyl ether coupling agent for multifunctional carbinol silicones, a method of producing catalyst-free RTV silicone networks at ambient conditions is presented. These silicone networks are proven chemically similar to a standard condensation-cured silicone and stoichiometric variations of PSz content demonstrate adjustable network properties.

Bioinspired High-Performance Silicone Elastomers by Catalyst-Free Dopamine Cross-Linking

“…In recent years, several green cross-linking systems have been reported (azidoalkyl cycloaddition, boron ester, Diels–Alder, etc.). Amino-functionalized polydimethylsiloxanes have attracted considerable interest from researchers due to their strong reactivity , and the availability of polymers of different molecular weights and functionalities for commercial use. − It allows catalyst-free cross-linking with a variety of cross-linkers, such as Aza-Michael reactions, − ureas from reaction with isocyanates, , and imine bonding through reaction with aldehydes . However, even though these reactions are already catalyst-free cross-linking systems, the adhesion properties of the prepared elastomers are relatively poor.…”

Photo‐Activity of Silacyclopropenes and their Application in Metal‐Free Curing of Silicones

“…All this emphasizes the necessity for novel metal‐free crosslinking methods. Alternative curing via autoxidation, [7,8] silacyclopropanes, [9] thiol‐enes, [10] polysilazanes, [11] or cyclic disulfides [12] has been introduced over the past years. While autoxidative curing can use readily available hydride‐terminated silicones, it is restricted to temperatures above 220 °C [8] .…”