Bio-based thiol-ene photo-cured resins derived from resveratrol and eugenol with excellent mechanical, flame retardant and dielectric properties

Thiol-ene photocurable resins have demonstrated significant potential for applications in flexible electronic packaging owing to their tunable mechanical properties, low polymerization energy requirements, and excellent dielectric characteristics. However, most of these resins are flammable with lots of fire hazards. To address this issue, we employed resveratrol, rich in aromatic ring structures and hydroxyl functional groups, to synthesize a biomass-derived monomer with carbon-carbon double bonds, namely RST. In addition, eugenol was used to react with hexachlorocyclotriphosphazene (HCCTP), yielding a reactive bio-based flame retardant additive (HECTP). It was cross-linked with pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) containing four thiol groups to prepare RST/4SH/HECTP resins. The results showed that the addition of HECTP remarkably enhanced the char formation ability and self-extinguishing performance. In particular, the total heat release (THR) declined from 19.2 kJ/g for RST/4SH to 13.6 kJ/g for RST/4SH/HECTP10 % with a reduction of 29.2 %. The loading of HECTP also enhanced the tensile strength and storage modulus of RST/4SH due to the improved crosslinking density of RST/4SH/HECTP resins. Moreover, the dielectric constant of RST/4SH was significantly reduced with the addition of HECTP. For RST/4SH/HECTP10 %, there was a dielectric constant of 1.78 that was lower than most reported results, highlighting its potential for electronic packaging materials.