s-Tetrazines are well known as click reagents for the modification of biomolecules and polymers that operate through a sequence of [4+2] cycloaddition to electron rich carbon-carbon double bonds and retro-[4+2] cycloaddition reactions with loss of nitrogen gas. The result is the installation of a dihydropyridazine group that can bear a variety of substituents. Recently, we discovered that some tetrazines were soluble and reactive with liquid polybutadienes allowing for facile cycloaddition modification. The s-tetrazine modification of polybutadiene adds sufficient mass to convert the liquid precursor into a solid polymer, foams the solidifying polymer with the evolved nitrogen gas, and provides a unique mechanism for crosslinking the polymeric foams. Here we present our results with the parent s-tetrazine’s (R = H) modification, foaming and crosslinking of polybutadiene and our model studies that were used to determine that crosslinking reaction likely proceeds through the oligomerization of the imine groups in the newly formed dihydropyridazine groups. Foams could be formed with as little as 2% tetrazine. Crosslinking also occurred at relatively low conversions of the double bonds, making this method a new potential, low temperature route to vulcanization of elastomers.

Foaming and crosslinking of polybutadiene with s-tetrazine

2019 Spring National Meeting

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