The effect of polyethylene glycoldiacrylate complexation on type II photoinitiator and promotion for visible light initiation system

In this work, we discussed the complexation effect between polyethylene glycoldiacrylate (PEGDA) and novel type II photoinitiator 2,6-bis(furan-2-ylmethylidene) cyclohexan-1-one(BFC). Due to this complexation effect, the initiating system BFC/PEGDA has broader ground state light absorption in visible light region than BFC has and could be initiated more efficiently by LED 405nm lamp (visible light source). Moreover, BFC/PEGDA exhibits higher initiating efficiency than BFC/ethyl-4-(dimethylamino) benzoate (EDAB) in initiating monomer such as hexamethylene diacrylate (HDDA). To investigate this unusual phenomenon, steady state photolyisis experiments of BFC, BFC/EDAB and BFC/PEGDA, H-1-NMR, time dependent density functional theory (TD-DFT) calculations were carried out. The results showed BFC exhibited weak photostability and photo bleached. The intramolecular motion of BFC induced few BFC performing hydrogen transfer interaction with coinitiator EDAB to produce radicals for polymerization. However, complex BFC/PEGDA has good photostability and this effect restricts the intramolecular motion of BFC which prevented BFC from being bleached and induced more BFC performing hydrogen transfer interaction with PEGDA to produce radicals for polymerization. According to H-1-NMR spectra of BFC in different radiation time and TD-DFT calculations of BFC's isomers, it demonstrated BFC performed intramolecular motion which was mainly caused by the furan rings rotating towards carbonyl on BFC. This strategy of promoting photoinitiator's absorption in the visible light region and its initiating efficiency just through mixing the two compounds together might provide potential application for visible light photoinitiating system.