Synthesis And Characterization Of Hydroxy Ketone Photoinitiators

Photopolymerization is a kind of green technology which is increasingly concerned because of its unique advantages.Photoinitiator is an important component in the photopolymerization system,and 1173 is a representative of free radical photoinitiators.The initiation process of 1173 is rapid and efficient,so it has been widely used and the research on 1173 and its derivatives has not stopped.In this project,a series of photoinitiators with different substituents were designed and prepared,and their photochemical properties and the ability of photoinitiation were studied.The main research contents and conclusions are as follows.1.polymerizable photoinitiator was designed and prepared.There was no obvious photodegradation and the induction period of polymerization was prolonged.However,it could still initiate monomers.Two kinds of photoinitiators,which were substituted by carbamate group,were synthesized.Compared to 1173,photodegradation was obvious and the initiation rate of photoinitiators was slower.The other two photoinitiators whose photoactivity were similar to 1173,had ethoxy group substitution structure.2.The structure of the photoinitiator had a significant impact on the properties.The photochemical activity of photoinitiators of(methyl)acrylate group substitution structure,carbamate group substitution structure and ethoxy group substitution structure decreased in turn.The reason was that superconjugation of the substituents with the 1173 group changed the structural stability of the photoinitiators.3.Polymerizable photoinitiators were prepared into macrophoto initiators by thermal polymerization.The photoinitiation-groupe on the side chain of the polymer had better photoactivity and initiation ability than the small molecule polymerizable photoinitiator.4.The production rate of free radical of polymerizable photoinitiator with stable structure was very slow.The free radical generating at primary stage copolymerized the polymerizable photoinitiator with monomer.The photoinitiation-groupe on the macromolecular chain had a rapid cleavage rate.As a result,two initiation methods facilitated the reaction together.5.In addition to the free radical polymerization by cleavage,polymerable photoinitiator with hyperconjugated structure was likely to undergo energy transfer in the excited state and generate active sites to directly initiate polymerization.