SynopsisWe report that aliphatic primary and secondary amines completely solubilize crosslinked silicone resins and rubber compositions at room temperature. The solubilization is attributed to nucleophilic cleavage of Si-0 bonds by amines, which apparently occurs selectively at crosslinking sites. The selectivity may reflect the presence of three oxygen atoma at such sites, which are expected to enhance the electrophilicity of silicon. On evaporation of amine, crosslinks are apparently regenerated as evidenced by solubility characteristics as well as f i l m properties of the reclaimed silicones. In addition to their theoretical interest, these results are potentially important from the standpoint of commercial applications as well, including the possible reclaiming of silicone-constituted furniture molds and the coating of heat-sensitive materials.During the course of studies on the application of solubility parameter methods for swelling cured we have found that aliphatic primary and secondary amines completely solubilize crosslinked siloxane polymers at room temperature. A major objective of this research was the development of solvent-based methods for facilitating the recovery of spores from plastic and rubbery materials utilized in spacecraft components. This goal was conveniently accomplished in high yields in the case of representative silicones by treatment with amines followed by plate counting methods (these results will be submitted elsewhere). Nevertheless, the unexpected finding of complete solubilization of cured silicones by amines prompted further studies on the nature of this interaction. The results are reported herein which indicate that amines react selectively at Si-0 crosslinking sites by nucleophilic substitution, as illustrated in eq. (1). Furthermore, the reversibility of this reaction is evidenced by the reformation of crosslinked sites on evaporation of amine. In addition to their theoretical interest, these results are potentially important from a technological standpoint as well, including the possible applications of reclaiming silicone-constituted furniture molds and coating of heat-sensitive materials.Initial studies were conducted with Dow Corning DC 840 silicone resin, which possesses a phenyl methyl polysiloxane backbone. The prepolymer also contains silanol (Si-OH) sites which are converted into Si-0-Si crosslinkages during curing. After curing at 24OOC for 1 hr, 50-mg samples (as cubes approximately 3 mm on a side) were suspended in 2 ml m i n e solvent
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