Synthesis And Character Of Low Migration Benzophenone Photoinitiator

As a green technology in the 21 st century,photopolymerization has been developing rapidly and was widely used in many fields,such as coatings,inks and adhesives,as well as in some high-tech fields like optoelectronics,laser imaging,stereolithography and nanotechnology.Photoinitiator is the key component for photopolymerization,which initiates the monomers and controls the curing speed and degree of initiating system.In this research,three specials of low migration photoinitiators were synthesized by two-step reaction based on traditional type II photoinitiator 4-(2-hydroxyethoxy)benzophenone(4-BP):the photopo ly mer izable photoinitiator named HEMA-IPDI-BP,the one-component photoinitiator named 4-BPAcPA,and the macromolecular photoinitiator named PPI 1 and PPI 2.Migration behavior of photoinitiators were studied by UV-Vis absorption spectra.The initiating efficiency of photoinitiators under different light intensity,photoinitiator concentration and monomers were investigated by real-time infrared spectroscopy(RT-IR).All the research could be concluded as follows.(1)The polymerizable photoinitiator HEMA-IPDI-BP was synthesized and characterized.The UV absorption spectra was similar as that of 4-BP while the photolysis rate was faster than 4-BP.In the photolysis experiments,the absorbance of 4-BP and HEMA-IPDI-BP was finally decreased 14.93%and 47.22%under same irradiation.Moreover,The extraction amount of films cured by 4-BP and HEMA-IPDI-BP was 60.43%and 39.52%than that of 4-BP,after immersed in acetonitrile solution for 5 days.Under the same conditions,the initiating efficiency of HEMA-IPDI-BP is higher than that of 4-BP.(2)The one-component bifunctional photoinitiator 4-BPAcPA was synthesized and characterized.The molar extinction coefficient of photoinitiator 4-BPAcPA was higher than that of 4-BP.Because there are hydrogen donors in the molecular structure,the photolysis rate is much faster than that of 4-BP.The final conversion of HDDA initiated by 4-BPAcPA was 84.99%,higher than 83.23%of BP/EDAB.The extraction amount of film cured by 4-BPAcPA was 37.23%and 24.34%than that of 4-BP and BP,after immersed in acetonitrile solution for 5 days.(3)Two macromolecular photoinitiators PPI 1 and PPI 2 which molecular weights was 4994 and 6675 respectively were synthesized and characterized.The UV absorption spectra was similar to that of 4-BP.The molar extinction coefficient of photoinitiator PPI 1 and PPI 2 was higher than 4-BP.The absorbance of 4-BP,PPI-1 and PPI-2 decreased by 15.85%,42.44%and 42.29%of the respective initial absorbances under 30 minutes of irradiation.Without the addition of EDAB,compared to 4-BPAC,PPI 1 and PPI 2,as the molecular weight(functionality)of photoinitiator increased,the polymerization rate increased and the final double bond conversion rate of HDDA increased.The final conversion of HDDA initiated by PPI 2 was 84.81%,higher than 83.23%of BP/EDAB.The extraction amount of film cured by PPI 2 was 39.96%and 24.61%than that of 4-BP and BP,after immersed in CH2Cl2 solution for 5 days.