Layered double hydroxides as a nanocontainer for encapsulating marine natural product antifoulant: Intercalation and tunable controlled release of cinnamate

Natural product antifoulant-inorganic clay composites such as cinnamate anion-intercalated Mg–Al-layered double hydroxides (CM-LDHs) with tunable particle size and high crystallinity are synthesized by acid–salt treatment combined with ion exchange. Structural analyses indicate that cinnamate anions are successfully intercalated into the LDH interlayer and form a distinct bilayer arrangement with cinnamate anions close to perpendicular to the hydroxyl layers. Kinetic simulation for the release data indicates that ion exchange is responsible for the release process, and the release mechanism of cinnamate anions from the LDH matrix in 3.5% NaCl solution can be tailored by adjusting the particle size. For CM-LDHs with particle sizes less than 2 μm, diffusion through the particle is implicated as the rate-limiting step; by contrast, for CM-LDHs with particle sizes larger than 3 μm, release satisfactorily followed a first-order equation. This hybrid material shows potential for application in active antifouling coatings for marine equipment.