Bis(4‐methoxybenzoyl)diethylgermane: A Highly Efficient Photoinitiator for the Polymerization of Vinylcyclopropanes

Abstract

Bis(4‐methoxybenzoyl)diethylgermane (BMDG) is used for the photopolymerization of six 1,1‐disubstituted 2‐vinylcyclopropanes (VCPs). A significantly higher photopolymerization reactivity compared to the conventional camphorquinone (CQ)/amine or CQ/amine/iodonium salt photoinitiator systems is observed. Furthermore, the influence of the electron‐withdrawing substituents on the monomer reactivity is investigated. 1‐Ethoxycarbonyl‐1‐ethylcarbamoyl‐2‐vinylcyclopropane 5 and 1‐ethoxycarbonyl‐2‐vinylcyclopropanecarboxylic acid 2 are found to be the most reactive monomers. 1,1‐Disubstituted VCP‐based dental composites containing BMDG are formulated. Those materials exhibit good mechanical properties as well as a low polymerization shrinkage. image