Self-healing thermally cued thiol–ene vitrimers utilizing bio-based tetraallylated cystamine and hexaallylated L-cystine

Bio-based vitrimers have attracted considerable attention owing to their potential contributions to carbon neutrality and resource efficiency. Herein, we report the synthesis and properties of thiol–ene network films prepared by the thermal curing of tetraallylated cystamine (A4CTA), tetrallylated 1,6-diaminohexane (A4DAH) and hexaallylated L-cystine (A6CST) with disulfide-containing polyether dithiol (LP-12) and pentaerythritol-based tetrathiol (S4P) at an allyl:thiol ratio of 1:1 in the presence of di-tert-butyl peroxide. Fourier-transform infrared spectroscopy revealed that the thiol–ene reaction proceeded almost completely. The degrees of swelling of the cured films decreased with decreasing feed LP-12/S4P ratio. The A4CTA- and A6CST-cured films with higher LP-12/S4P ratios exhibited lower glass transition temperatures, tensile strengths and tensile moduli, and could be healed at lower temperatures. The A4CTA-based cured films exhibited higher healing efficiencies (ησs) than the A4DAH- and A6CST-based ones at the same LP-12/S4P ratio. The A4CTA-based film with the highest LP-12/S4P ratio exhibited the highest ησs (60% at room temperature and 81% at 100 °C for 24 h) and could be self-healed at least three times by treating at 100 °C for 24 h. These findings demonstrate that the molecular design of allylated amines and thiol components significantly affects the thermal and self-healing properties of bio-based vitrimers.