Synthesis of tetraallylated cystamine and the study of its performance as a curing agent for the epoxy/thiol-ene photopolymerization of biobased nopol epoxy resins

This article reports the synthesis of a bio-inspired curing agent, the tetraallyl cystamine (TAC) and the evaluation of its performance to photocure two epoxy resins derived from the terpenoid nopol, by using the epoxy/thiol-ene photopolymerization technique. The curing agent was prepared in two stages: a) reaction of the diallylamine with ethylene disulfide, through a mercaptoethylation reaction and b) oxidation of the obtained thiol to disulfide, using dimethylsulfoxide as an oxidizing agent. To the epoxy resins was added the curing agent TAC, pentaerythritol tetrakis (3-mercaptopropionate) and dimethoxyphenylacetophenone, to obtain cross-linked co-networks of the polyether-polythioether type. A trifunctional nopol epoxycycloaliphatic epoxy resin and an epoxycycloaliphatic-glycidyl nopol epoxy resin were evaluated, with the former displaying higher reactivity, higher modulus and higher thermal stability.