Highly reactive novel biobased cycloaliphatic epoxy resins derived from nopol and a study of their cationic photopolymerization

In this work three biobased epoxy monomers derived from nopol were successfully prepared. Different strategies were employed to synthesize the monomers, such as alkylation of nopol with epichlorohydrin, nucleophilic aromatic substitution using the alkoxide of nopol and cyanuric chloride, and acetalization of nopol with 3-cyclohexene 1-carboxyaldehyde. All unsaturated intermediates were subsequently epoxidized using dimethyl dioxirane as the oxidizing agent. The kinetics of photopolymerization demonstrated that the three synthesized epoxy monomers exhibited high reactivity due to the highly strained epoxy group situated in the already highly strained bicyclic structure of nopol. The glass transition temperatures determined by Differential Scanning Calorimetry (DSC) were 66 °C and 60 °C for the trifunctional monomers 2, 4, 6-tris (2-(7, 7-dimethyl-3-oxatricyclo [4.1.1.0 2,4 ] octan-2-yl) ethoxy)- 1, 3, 5-triazine ( N2 ) and 2,2′-(((7-oxabicyclo [4.1.0] heptan-3-yl methylene) bis (oxy)) bis (ethane-2,1-diyl)) bis (7, 7-dimethyl-3-oxatricyclo [4.1.1.0 2,4 ] octane) ( N3 ) respectively, and of 12 °C for bifunctional monomer 7, 7-dimethyl-2- (2-(oxiran-2-yl-methoxy) ethyl)-3-oxatricyclo [4.1.1.0 2,4 ] octane ( N1 ). The aromatic triazine epoxy monomer N2 displayed the highest thermal stability in comparison with the other two monomers, with an onset of degradation of 302 °C as determined by the Thermogravimetric Analysis (TGA).