Exploring the segregating and mineralization-inducing capacities of cationic hydrophilic polymers for preparation of robust, multifunctional mesoporous hybrid microcapsules.

A facile approach to preparing mesoporous hybrid microcapsules is developed by exploring the segregating and mineralization-inducing capacities of cationic hydrophilic polymer. The preparation process contains four steps: segregation of cationic hydrophilic polymer during template formation, cross-linking of the segregated polymer, biomimetic mineralization within cross-linked polymer network, and removal of template to simultaneously generate capsule lumen and mesopores on the capsule wall. Poly(allylamine hydrochloride) (PAH) is chosen as the model polymer, its hydrophilicity renders the segregating capacity and spontaneous enrichment in the near-surface region of CaCO3 microspheres; its biopolyamine-mimic structure renders the mineralization-inducing capacity to produce titania from the water-soluble titanium(IV) precursor. Meanwhile, CaCO3 microspheres serve the dual templating functions in the formation of hollow lumen and mesoporous wall. The thickness of capsule wall can be controlled by changing the polymer segregating and cross-linking conditions, while the pore size on the capsule wall can be tuned by changing the template synthesizing conditions. The robust hybrid microcapsules exhibit desirable efficiency in enzymatic catalysis, wastewater treatment and drug delivery. This approach may open facile, generic, and efficient pathway to designing and preparing a variety of hybrid microcapsules with high and tunable permeability, good stability and multiple functionalities for a broad range of applications.