pH-Dependent Switchable Permeability from Core–Shell Microcapsules

We recently reported cationic cyclopolymerization of o -vinylbenzaldehydes initiated by boron trifluoride to generate acid-sensitive poly( o -(α-alkyl)vinylbenzaldehyde). Herein we report preparation of core–shell microcapsules (μCs) using flow-focusing microfluidic techniques with shells composed of poly( o -(α-methyl)vinylbenzaldehyde) (PMVB) that release their payload in response to dilute aqueous acid solution. Release profiles of encapsulated fluorescein isothiocyanate-labeled dextran from μCs are controlled by varying the proton concentration and shell-wall thickness. SEM studies indicate that the system’s unique reversible release mechanism involves porosity changes in the shell wall due to microcrack formation.