New allyl-functional catalytic comonomers for sequential thiol-Michael and radical thiol-ene reactions
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Soft poly(thioether) thermosets have been synthesized by employing a two-step curing procedure based on click chemistry. The first stage of curing is a thiol-Michael addition between acrylates (or methacrylates) and thiols in excess, catalyzed by a set of novel tertiary amine catalyst comonomers with allyl functionality. Subsequently, the pendant allyl groups of the comonomer get incorporated into the polymer network by undergoing thiol-ene UV photopolymerization with the remaining thiols. The strong catalysis by the high concentration of tertiary amine groups facilitates quantitative conversions at the end of the first stage. All remaining functional groups are depleted after a short period of UV irradiation. Final materials are clear, transparent, and exhibit homogeneous network structures with alpha relaxation temperatures in the range 3–25¿°C. This sub-ambient relaxation temperature range suggests these materials may be suitable for coating applications where delicate substrates are involved such as plastic, wood and paper.
CitationKonuray, A., Fernandez-Francos, X., Ramis, X., Serra, M. À. New allyl-functional catalytic comonomers for sequential thiol-Michael and radical thiol-ene reactions. "Polymer", 28 Febrer 2018, vol. 138, p. 369-377.