Low migration type I photoinitiators for biocompatible thiol-ene formulations

Abstract

In this contribution, polymerizable hydroxyalkyl phenone (PI-4) and monoacylphosphine oxide (PI-9) based photoinitiators (PIs) bearing alkyne groups were synthesized with the aim to realize low PI migration together with a high photoactivity in biocompatible vinyl carbonate/thiol resins. Although, photo-DSC measurements showed that the initiation performance of PI-4 in the present formulation is lower than the photoactivity of the reference PI Irgacure 2959 (I2959), it turned out that its migration is significantly reduced compared to I2959. This fact is explained by the copolymerization of the alkyne functionality via a thiol/yne reaction as revealed by real-time FT-IR measurements, leading to a covalent immobilization of this PI in the polymeric network. Most importantly, the alkyne functionalized monoacylphosphine oxide based PI provides almost similar initiation activity as its reference PI Irgacure TPO-L (TPO-L) while exhibiting 40% lower migration than the non-functionalized TPO-L. These findings make PI-4 and PI-9 promising candidates for their application in biocompatible vinyl carbonate/thiol formulations, in which low migration of the PI is desired.