Substituted cyanoacrylate-based dynamic covalent polymers with intrinsic antioxidation and UV-shielding via cascade thiol-ene addition and Knoevenagel condensation

Abstract

Ultraviolet irradiation and oxidation are the primary factors causing aging in living organisms and organic materials. This study presents a multifunctional chemical group, ​substituted cyanoacrylate (SCA) group, which exhibits ​strong ultraviolet absorption capability​, excellent antioxidant property. Concurrently, SCA groups undergo ​C=C bond metathesis reactions under thermal activation, endowing crosslinked networks with ​reprocess ability. ​Through synthesis of small-molecule model compound, the UV-absorption and antioxidant characteristics of substituted cyanoacrylate groups were experimentally confirmed. ​Based on a cascade reaction combining thiol-ene addition and Knoevenagel condensation, we synthesized linear polymers with C=C bonded backbones. This polymer exists as a viscous liquid at ambient temperature (M_n = 3,700 g/mol, T_g = -19°C), functioning as a ​polymeric UV-absorber/antioxidant. Furthermore, dynamic covalent polymer networks (DCPNs)​​ were prepared using the same reaction with tetrathiol monomers as cross-linkers. This SCA-based DCPN demonstrates ​high mechanical strength​ (tensile strength > 17 MPa, elongation at break > 175%), ​high optical transparency​ (>90% transmittance for red light), unique UV/oxidation resistance and reprocess ability. These properties establish the material as a sustainable protective coating suitable for demanding applications.