Reversible pH‐Dependent Properties of Multilayer Microcapsules Made of Weak Polyelectrolytes

Abstract Summary: We investigated microcapsules composed of the weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) assembled on calcium carbonate cores. These capsules are stable in the pH range from 2.5 to 11.5, undergoing reversible swelling in the pH interval from 2.7 to 2.6. Capsule swelling occurs at a protonation degree above 90%. The pH‐dependent size variation of PAH/PMA capsules is blocked after crosslinking of the polyelectrolyte layers. Schematic of the swelling and de‐swelling of the capsules with changing pH. image Schematic of the swelling and de‐swelling of the capsules with changing pH.