Pore-formation through Controlling Noncovalent Interactions in Polyelectrolyte Film

Layer-by-layer assembly (LbL) polyelectrolyte film driven by electrostatic interaction is fabricated from alternate deposition, which has garnered broad interest all over the world in the fields of anti-bacteria, antifouling, separation, sensor, etc. The mobility of polymeric chains plays a vital role in the dynamic and structural control of polyelectrolyte film. Owing to the intrinsic sensitivity of electrostatic interaction for the external environment, the mobility of polymeric chains could be adjusted, and then their structures could be dynamically tuned. However, few studies have illuminated the specific role of polyanion or polycation in these procedures. Our proposal is based on a polyelectrolyte film with azobenzene (Azo) interaction, whose structure could be dynamically and reversibly controlled under the action of ultraviolet (UV) irradiation, acid treatment, and water plasticization. Herein, azobenzene were grafted onto poly(acrylic acid) (PAA) through amidation reaction. The poly(ethyleneimine)/PAA-Azo (PEI/PAA-Azo) film, which contained two kinds of noncovalent interactions, was fabricated by the LbL technique. Porous structures were constructed in PEI/PAA-Azo film after UV irradiation in a bath of the acid solution, while the film kept solid without UV irradiation after acid treatment. Patterned porous PEI/PAA-Azo film was obtained after regional UV irradiation and acid treatment. Thanks to the reversibility of azobenzene interaction and electrostatic interaction, the patterned porous structures were constructed reversibly. Furthermore, CdSe/ZnS quantum dots were spatially encapsulated into the film to develop a pattern that was visible in UV light but invisible in visible light. Through lubricate-infusion in porous regions, a patterned antifouling surface was fabricated, where patterned biofilm was cultured successfully. This study presented a feasible strategy for realizing the importance of polyanion mobility for the structure and dynamics of polyelectrolyte film, and it opened a broad window for the applications (such as information storage, information security, and bacterial bioengineering) of polyelectrolyte film.