An initiating system with high efficiency for PEGDA photopolymerization at 532 nm

Nanogels based Polyethylene glycol diacrylate (PEGDA) attracted much attention due to their promising application in drug delivery and tissue engineering. Here, PEGDA photopolymerization at 532 nm with different initiating systems was investigated. Nanogels can be obtained using single 2′,4′,5′,7′-tetrabromofluorescein disodium salt (EY) as the photoinitiator. To increase the polymerization rate, EY, triethanolamine (TEOA), and diphenyl iodonium hexafluorophosphate (DPI) were investigated as a three-component initiating system. With that initiating system, the conversion of PEGDA double bond was higher than 90 % in 1 min at extremely low irradiation energy density (P= 0.95 mW/cm 2 ). However, the conversion of PEGDA double bond was only 51.5 % in 1 min at the same irradiation energy density when using EY and TEOA as two-component initiating system. Subsequently, the corresponding mechanism of the three-component (EY-TEOA-DPI) initiating system was illustrated. DPI might participate in two ways of photooxidation and reduction, which dramatically improved the polymerization rate. The EY-TEOA-DPI initiating system is promising to be applied in the preparation of multifunctional hydrogels.