Comparative release rates from controlled release polymer coatings—comparisons between models and experiment

Controlled release devices and coatings are used heavily in widely varying applications. Here, we focus on applications to antifouling coatings by adding an active agent to polymeric coatings. Quantitative models were developed for four distinctively different methods of dispersing the active agent in the coating. The predicted release rates from these models were contrasted to reveal the inherent differences in the time-dependent release rate profiles achievable from these types of coatings. The majority of these four coatings (monolithic, dispersed particle and reservoir membrane) release the active agent with greatly varying rates over their effective lifetimes, while a microcapsule-based coating has the potential to produce relatively constant rates of release. While the models are potentially of great value, they require a number of parameters, particularly the diffusion coefficient of the active agent through the polymer, to be quantified. We demonstrate how such parameters can be quantified through release rate measurements from simple experimental coatings.