Preparation and properties of phosphorous-nitrogen containing UV-curable polymeric coatings based on thiol-ene click reaction

Thiol-ene click reaction is an efficient method for the rapid production of films with desirable properties. Compared with common UV-curing techniques, it largely eliminates the problem of oxygen inhibition and is of inherent low internal stress. In this work, two phosphorous-containing diene monomers and one nitrogen-containing trithiol monomer were designed and synthesized. The UV-curing reaction kinetics of the different ene groups (allyl ether, acrylate, and methacrylate) with the thiol group were studied using real-time FTIR. The competition between the thiol-ene free radical polymerization and homopolymerization of the CC double bond were evaluated and tuned by varying the ratio of the ene and thiol functionalities. Highly cross-linked coating with excellent hardness, adhesion and flexibility are obtained as a result of the high efficiency of thiol-ene click reaction and its inherent low internal stress, as well as the incorporation of hetero-atoms P and N to the polymer back bone. The incorporation of phosphorous and nitrogen to the system also improved the flame retardancy of the film due to a positive phosphorous-nitrogen synergistic action.