Pros and cons of coating layered double hydroxide nanoparticles with polyacrylate

Preventing the aggregation of layered double hydroxide nanoparticles (LDH-NP) and producing additional functionality are two important objectives for their applications as drug nanocarriers, among others. Adsorption of polyelectrolytes like polyacrylate (PA) is a promising approach to produce protective, functional coatings, but the effect of factors such as chain length, as well as the pros and cons of this strategy, have not been described. In this work, these aspects were studied using LDH-NP intercalated with chloride and benzoate as interlayer probes. The interaction between LDH-NP and PA, as well as the effect in the aggregation of the former, was studied as a function of the molecular weight (MW = 1.2, 8.0 and 450 kDa) and the PA concentration. High MW were more effective for preventing LDH-NP aggregation as well as for minimizing the PA intercalation between the layers, Thus, the 8.0 kDa PA allowed obtaining benzoate intercalated LDH-NP with a particle size around 200 nm that maintained 40% of the exchange sites occupied by benzoate anions. PA coating not only hindered aggregation and changed the particle charge, but also provided new functionality, such as a protective layer towards proton diffusion and, consequently, dissolution of LDH-NP. PA coating is then an effective tool for LDH-NP stabilization and customization, if interlayer anion loss is controlled.