Exploring functionalized benzophenones as low-migration photoinitiators for vinyl carbonate/thiol formulations

[Display omitted] •Polymerizable benzophenone derivatives feature high photo activity in Thiol-ene resins.•Alkyne modified benzophenones are immobilized in the polymeric network.•The migration behavior of polymerizable benzophenones is significantly reduced. In this contribution, benzophenone (BP) derivatives bearing vinyl carbonate, but-1-yn-4-yl ester, and propargyl ester groups were synthesized and evaluated as polymerizable photoinitiators (PI) in a thiol/vinyl carbonate formulation, with the aim to realize low-cytotoxic and highly photoreactive resins featuring low PI migration in the cured state. Compared to their performance in pure butanediol divinyl carbonate (BuVC), these PIs provide decent initiation performance in BuVC/thiol formulations, which can be attributed to the step growth based network formation facilitating a high mobility of the excited BP and subsequently formed radicals below the gel point. Most importantly, the but-1-yn-4-yl ester functionalized PI offers higher curing speed and almost similar double bond conversion as the reference PI bearing a non-polymerizable ethyl moiety, while the leachability of this BP derivative is significantly reduced. This makes this PI a promising candidate for the realization of low-migration thiol/ene resins.