Novel polystyrene sulfonate–silica microspheres as a carrier of a water soluble inorganic salt (KCl) for its sustained release, via a dual-release mechanism

Herein we describe a novel type of organic–inorganic composite solid microsphere, comprised of polystyrene sulfonate and silica (PSS–SiO2), which has been synthesised from polystyrene sulfonic acid and tetraethyl orthosilicate. The microsphere can (i) encapsulate a low molar mass (<100 Da) inorganic salt (KCl), and (ii) provide sustained release (>48 hours) of the salt from the microspheres to an aqueous environment, which has hitherto not been possible. We propose a novel dual-release mechanism of the salt from the microspheres, which leads to the sustained release, and therefore has potential applicability for the controlled and prolonged release of other actives.