Microemulsions Encapsulated Nicotine as Plant-Derived Antibacterial and Antifoulant for Epoxy Coatings

Antifouling coatings incorporated with the antifoulants offer a more economical choice than the self-polish and low-surface-energy antifouling coatings, because of their complexing resin modifications and relatively high costs. Traditional antifouling agents, such as organotin compounds and cuprous oxide, have been restricted or partially prohibited due to their environmental toxicity. In contrast, some plant extracts exhibit promising antifouling properties and have attracted attention as an environmentally friendly antifoulant in various liquid coatings. Nicotine, a natural and biodegradable plant alkaloid from tobacco, has been demonstrated to effectively inhibit marine biofouling and cell proliferation. However, the direct introduction of nicotine to the base coatings may cause rapid and burst release. This study develops a stable oil-in-water (o/w) sustained-release microemulsion encapsulating nicotine by an “egg-box” cross-linking method with sodium alginate and metal ions. In this microemulsion, nicotine exists both in the alginate “egg-box” structure by physical encapsulation and in the ionic binding state with alginate chains. The prepared microemulsion exhibits good stability and compatibility with epoxy coatings, as well as promising antibacterial, antialgal, and antifouling performances attributed to the sustained release of nicotine. This study finds a new approach to nicotine in the field of fine chemicals but not the traditional scope of cigarettes.