1,2,4,5-Tetrazines are generally built into polymers in order to modify the optical or electronic properties of the materials. In this talk, I will describe our use of tetrazines as <i>monomers</i> in cycloaddition copolymerizations with diethynylbenzene and as a <i>reactive modifier and blowing agent</i> for converting polydienes into foams. In both cases we take advantage of the tetrazine reacting as a diene in cycloaddition reactions. Tetrazines react with alkynes by a [4+2] cycloaddition followed by a cheletropic elimination of dinitrogen to afford pyridazines. Pyridazines can undergo a second set of cycloaddition/retro cycloaddition reactions with an alkyne to afford a benzene ring. Reacting a tetrazine with diethynyl benzene gives rise to disubstituted poly(biphenylenes). Alternatively, tetrazines react with alkenes with loss of dinitrogen to give a dihydropyridazine that can either oxidize to a pyridazine, or undergo rearrangement. When tetrazines are added to neat, liquid polydienes, the cycloaddition increases the glass transition temperature of the polymer while the nitrogen gas acts as a blowing agent that foams the polymer. Depending on the tetrazine:polydiene stoichiometry, the nature of the substituents on the tetrazine and whether or not the polydiene has hydroxy end groups, the product can be an elastomeric, thermoplastic or thermoset foam.

New materials using tetrazines as monomers, or polymer modifiers and blowing agents

251st National Meeting (2016)

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