Biobased Coatings Based on Eugenol Derivatives.

We have fabricated plant-based coating materials using urushiol analogues that were synthesized via a simple three-step route from eugenol (4-allyl-2-methoxyphenol), an allyl-substituted guaiacol. To mimic the chemical structure of urushiol, the allyl chain of eugenol was substituted with alkyl thiols by a thiol-ene reaction. The guaiacol backbone was modified to a catechol backbone through a silylation/desilylation reaction. Uniform thin films were obtained on various substrates by spin-coating a solution of the urushiol analogues and iron(II) acetate. The physical and chemical properties of these films were comparable to those of urushiol thin films, and the adhesion, mechanical strength, and antioxidant properties were superior. The hydrophobicity and Young's modulus of the film increased with the increase in the alkyl chain length. Because various functional units can be introduced to the catechol backbone, our method could be used to fabricate environmentally sustainable, multifunctional, high-performance coatings from eugenol.