Synthesis and Evaluation of Vinyl-Substituted Aminosilane Oligomers as Preceramic Coatings for Corrosion Protection

With interest in exploring their effectiveness for corrosion protection, vinyl-substituted aminosilane oligomers were prepared from a variety of precursors through both traditional aminolysis and modern dehydrocoupling strategies. The addition of vinylphenyldichlorosilane to ethylenediamine resulted in substitution to yield the corresponding silane diamine copolymer; however, this product was not found to produce a uniform coating when it was applied to copper. In a complementary methodology, (^Ph2PPrADI)Co was used as a catalyst for the dehydrocoupling of vinyltris(dimethylsiloxy)silane with either ethylenediamine or 1,6-hexanediamine to generate siloxane diamine oligomers that featured near quantitative Si-H amination. While the product derived from ethylenediamine was found to afford a coating with a single-coat thickness of 38 μm, it was not effective at preventing copper surface corrosion upon exposure to 1.0 M HCl. In contrast, the (^Ph2PPrADI)Co-mediated dehydrocoupling of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasilazane to vinyltris(dimethylsiloxy)silane or trimethylsilyl-terminated poly(methylhydrosiloxane-<i>co</i>-dimethylsiloxane) afforded polysiloxazane oils that offered thermally robust and acid-resistant coatings upon curing.