The 1,3-bis(dicyanomethylidene)indane skeleton as a (photo) initiator in thermal ring opening polymerization at RT and radical or cationic photopolymerization

Abstract

1,3-Bis(dicyanomethylidene)indane is presented as a new initiator for ring opening polymerization of epoxides at RT. This compound behaves as a strong acid (AH) with an associated basic form (A⁻) that does not inhibit the propagation of the cationic polymerization. Remarkably, A⁻ is characterized by a strong visible light absorption and can also photosensitize iodonium salt decomposition. A new iodonium salt based on A⁻ as a counter-anion is proposed. This latter compound exhibits unusual properties: (i) excellent absorption in the 300–700 nm wavelength range and (ii) a free radical initiating ability for λ > 300 nm. The chemical mechanisms are investigated by ESR, fluorescence and steady state photolysis experiments.