Polymer Coatings Comprised Entirely of Soft and Semipermeable Microcapsules

Abstract

We report the fabrication and characterization of surface coatings that consist entirely of networks of hollow and semipermeable polymeric microcapsules. These assemblies incorporate many useful functions of individual microcapsules into coatings with unique compartmentalized structures. Iterative immersion of substrates into suspensions of microparticles coated with polymer multilayers presenting either (i) amine or (ii) amine-reactive azlactone functionality resulted in the reactive/covalent layer-by-layer assembly of coatings of colloidal particles. Removal of particle cores yielded compartmentalized coatings consisting of semipermeable hollow capsules that were physically stable in aqueous media and upon drying and rehydration. Confocal microscopy and scanning electron microscopy (SEM) revealed these assemblies to have disordered structures with some apparent hints of stratification resulting from the iterative assembly process. Residual azlactone groups in the capsule walls enabled tailoring of interfacial properties and controlled release behaviors by treatment with hydrophobic or hydrophilic amines. Fabrication of hollow-capsule assemblies on sacrificial substrates permitted triggered delamination and subsequent transfer of these coatings to secondary surfaces. The coatings reported here are mixtures of two different kinds of hollow reactive capsules. This iterative approach could also be used to design coatings comprising many different types of capsules with different properties (e.g., different types of encapsulated cargo or degrees of permeability). The structures and properties of these hollow-capsule coatings could thus prove useful in many applied contexts ranging from catalysis and controlled release to the development of soft material coatings with tunable interfacial or mechanical properties.

A decade of developing applications exploiting the properties of polyelectrolyte multilayer capsules

“…Potential applications in catalysis and controlled release have been carried out. 433 Excellent mechanical strength of the wall of microcapsules ensures possible protection for vulnerable objects such as probiotic bacteria. Microencapsulation is recognized as one effective way to enhance probiotic bacteria survival.…”