Synthesis and polymerization of vinylcyclopropanes

Vinylcyclopropanes are important synthetic intermediates in organic chemist ry and are mostly synthesized by the simultaneous introduction of the cyclo propane and the vinyl unit, e.g., by the reaction of trans-1,4-dihalobutene s with beta-dicarbonyl compounds or the addition of carbenes to dienes. The polymerization of vinylcyclopropane itself results in vinyl polymers with predominantly 1,2-structural units. The radical polymerization of substitut ed vinylcyclopropanes results in polymers with mainly IJ-ring-opened units, whereby radical stabilizing substituents or electron-withdrawing groups in crease the radical polymerizability and the ring-opening ability. The vinyl cyclopropanes undergo a radical copolymerization with other vinyl monomers, such as methacrylates, and, in comparison to the polymerization of these l inear vinyl monomers, the vinylcyclopropanes show a significantly lower vol ume shrinkage during ring-opening polymerization. Hybrid vinylcyclopropanes are polymerized step-by-step under formation of reactive polymers or polym er networks. Multifunctional cross-linking vinylcyclopropanes can be used a s new low-shrinking matrix monomers for photopolymerizable materials. In ad dition, the sol-gel process of trialkoxysilyl-functionalized vinylcycloprop anes affords low shrinking organic-inorganic nanocomposites.