Preparation Of One Component Benzophenone Photoinitiators

Photopolymerization is a green technology because it's efficient,energy saving,economical,enabling and environmental friendly,so it is widely used.Photoinitiator is the key component of photocuring systems as polymerization begins with the active species(free radicals or cations)grew out of photoinitiator which absorbs light energy.However,photodissociation products of photoinitiators or co-initiators for type ?photoinitiators may migrate out of the cured layer,and these migrated molecules could do harm for performance of products,users,and the environment.For example,the type ? initiator and hydrogen donor need to be used cooperatively,the small molecular tertiary amine,which has adverse effects such as odor and potential toxicity,is frequently used as an efficent hydrogen donor.Currently,the common methods for reducing the migration of the initiator are to prepare macromolecular photoinitiators(increasing the molecular weight is effective to reduce the mobility of the molecule),one-component photoinitiators and the polymerizable photoinitiators(ensuring that they are covalently bonded to the networks of polymers).In order to avoid the use of small molecular amines without affecting the performance of initiators,a series photoinitiators with different amount of functional groups were prepared by introducing different types of amines into the benzophenone derivatives containing acrylate double bonds through Michael addition reaction,then systematicly studied their migration performance and initiating properties.In this paper,monofunctional,difunctional,and multi-functional benzophenones were prepared by reacting self made 4-(2-acryloyl-oxyl-ethoxyl)benzophenone with a variety of amines,and the structures of the products were determined by infrared spectroscopy and nuclear magnetic resonance spectroscopy;UV absorption spectroscopy showed UV absorption of the one-component initiators is basically the same as raw material and 4-(2-hydroxyl-ethoxyl)benzophenone;due to the introduction of tertiary amines in the structrues,the photodegradation rate of the one-component photoinitiators synthesized under the same ultraviolet light conditions here are obviously improved;in addition,through the acetonitrile extraction experiment,it can be seen that the amount of extractable residues of the initiators migrated from the cured films in acetonitrile can be significantly reduced,the UV absorption curves of different extraction times shows that the migration rate of the one-component photoinitiator in the cured films is significantly reduced.Finally,the polymerization kinetics measured by real-time infrared spectroscopy have shown that,in addition to the bifunctional initiator synthesized with benzylamine,for initiating the polymerization of the same monomer,the other initiators showed the higher conversion rate than 4-(2-acryloyl-oxyl-ethoxyl)benzophenone,4-(2-hydroxyl-ethoxyl)benzophenone and benzophenone,it is proved that the synthesized one-component photoinitiators have a better performance.