The Search for a Highly Efficient Long-Wavelength Photoinitiator by Increasing Aryl Conjugation: From Computational Design, Characterization, and Potential Application

摘要

Currently, dental composites are limited to layer-by-layer deposition due to depth curing limitations using blue light. In dental composites, monomers are polymerized by light with the presence of photoinitiators (PI). Free-radicals, which promote polymerizations of vinyl monomers, are formed when PIs are excited by irradiation (either UV or visible light). A widely used photoinitiating system in the dental industry consists of a combination of camphorquinone and ethyl 4-dimethylaminobenzoate. The drawback in the usage of this method is the yellow coloring and stability of these PIs. There is a current demand for a PI that initiates curing in the visible light with high efficiency. This demand is not only needed in the dental industry, but also in fields such as laser 3D printing and regenerative medicine. In this study, three new photoinitiators (2-Naphthacene (APO), 9-Anthracene (APO), and 9-Anthracene (BAPO) were synthesized, characterized, and evaluated for its potential application for visible light curing. UV-vis spectroscopy results show that increasing the aromaticity of the PI increases the wavelength of absorption as well as the molar extinction coefficient. However, IR kinetics and Real Time UV-vis spectroscopy results show that the efficiency of the radicals from the photoinitiators are drastically infringed based on the stabilization effect occurring on the radicals. These above mentioned PIs can help us understand the design of a PI with greater efficiency in the visible light curing. In addition, they may potentially replace the current initiating systems used in the dental industry as well as other photochemistry based fields.