The use of biophenols to develop bioantioxidants is devoted to sustainable development, reducing energy and environmental issues. In order to step closer to practical application, bioantioxidant effectiveness is as important as renewability. A novel intramolecular synergism strategy aiming at high-efficiency oxidative inhibition is proposed by combining biobased phenol and arylamine in one molecule. Mannich condensation of hydrogenated cardanol (HC) with arylamines and paraformaldehyde led to the formation of three phenol-arylamine antioxidants (BAs). BAs were characterized by HRMS, FT-IR, NMR, and thermogravimetic (TG) analysis. Free radical scavenging activity of BAs was assessed using a DPPH (1,1-diphenyl-2-picrylhydrazyl) method, and was found to be much higher than that of commercial antioxidants. BAs were evaluated as antioxidant and thermal-oxidative stabilizer in polyol in terms of pressure differential scanning calorimetry (PDSC), rotary bomb oxidation tests (RBOT), and TGA. In a comparison to commercial antioxidants, BA1 demonstrated superior antioxidant properties and thermal-oxidation stability, which mostly benefit from intramolecular synergism.

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