Aza-Michael silicone cure is accelerated by β-hydroxyalkyl esters

The aza-Michael reaction is proving to be a practical, catalyst free method by which a variety of polymers, including silicones, can be cured. However, its adoption may be compromised by slow cure rates; for many applications is it not practical to accelerate cure by heating. OH groups on the amine, acrylate partner or solvent are known to lead to accelerated rates of aza-Michael reactions. The impact of the location of OH groups on reaction partners is demonstrated using both small molecules and small molecules plus telechelic silicones. While all OH groups are shown to increase reaction rates, a special enhancement is provided by beta-hydroxyalkyl acrylate esters, which have significantly higher rates of reaction than simple acrylates per se, and yet higher reactivities in hydroxylic media. Using this motif, in the absence of solvents, silicone elastomer cure based on the beta-hydroxyalkyl acrylate motif is facile and complete in less than 30 min at room temperature.