Bio-based polymer networks by thiol–ene photopolymerizations of allyl-etherified eugenol derivatives

• New bio-based polymer networks were prepared from allyl-etherified eugenol derivatives.
• This is the first example of thiol–ene photopolymerization of eugenol derivatives.
• Progress of the reaction was analyzed by FT-IR spectroscopy in detail.
• Relation between structure and properties of the cured resins was clearly elucidated.

Allyl-etherified eugenol (AEG) was synthesized by the reaction of eugenol and allyl bromide in the presence of sodium hydroxide. 1,3-Diallyl-4-allyloxy-5-methoxybenzene (DAEG) was also synthesized by a similar allyl-etherification reaction of 2,4-diallyl-6-methoxyphenol (rAEG) which was produced by the Claisen rearrangement of AEG. Thiol–ene photopolymerization of AEG or DAEG with pentaerythritol-based primary tetrathiol (pS4P), pentaerythritol-based secondary tetrathiol (S4P) or isocyanurate-based secondary trithiol (S3I) at allyl/SH 1/1 produced photo-cured resins (AEG-pS4P, AEG-S4P, AEG-S3I, DAEG-pS4P, DAEG-S4P or DAEG-S3I). Glass transition temperature of every photo-cured resin was in the range from 4 to 9 °C. AEG-pS4P and DAEG-pS4P displayed higher 5% weight loss temperatures (378.3 and 367.9 °C, respectively) than the other cured resins (351–344 °C). DAEG-pS4P, AEG-pS4P and AEG-S3I displayed the highest tensile modulus (32.9 MPa), strength (0.98 MPa) and elongation at break (58.7%) among all the photo-cured films, respectively.

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