Controlling Structural Transformation of Polyelectrolyte Films for Spatially Encapsulating Functional Species.

Although many approaches have been developed to encapsulate functional species into polyelectrolyte films, few of them can effectively control the final distribution of these ones. Herein, a facile strategy is proposed to spatially control the encapsulation of guest species by locally regulating the structural transformation of polyelectrolyte films. Patterned porosity is created within a film by cross-linking it selectively and then immersing it in an acidic solution. These porous regions can exhibit significantly different properties from other regions, including the ability to wick solution, a greater retention of guest species, and the capability of structural transformation. After loading guest species, the porous structures can be eliminated at saturated humidity to encapsulate the guest species into the film, leading to their patterned distribution across the film. Based on this method, various guest species, ranging from fluorescent dyes to nanoparticles, can be locally encapsulated into polyelectrolyte film, forming distinct patterns of arbitrary shapes and sizes and thus paving the way for further applications.