Morphology and Properties of Microcapsules with Different Core Releases

The morphology, mechanical properties, and permeability of hydrogen-bonded layer-by-layer (LbL) microcapsule shells assembled on cubic CdCO3 cores have been studied in comparison with traditional shells assembled on spherical SiO2 cores. We observed that the morphology of LbL shells is dramatically affected by the different release processes with highly porous and softened LbL shells as a result of the intense CO2 gas formation and ion release during the removal of cubic CdCO3 cores. A substantial increase in porosity is reflected in a dramatic change in the mesh size of LbL shells, from 2 nm for spherical capsules to above 35 nm for cubic capsules. Shells also possess enhanced permeability with a many fold increase in diffusion coefficient for dextran molecules and enhanced softening with the elastic modulus dropping by almost an order of magnitude for cubic capsules. These dramatic changes in shell morphology, porosity, permeability, and stiffness, observed in this study for the first time, are all important for the intelligent projection of controlled loading and unloading behavior of microcontainers with different shapes and composition, a component usually overlooked in current studies.