Synthesis of pH-Responsive Polymer Sponge Coatings and Freestanding Films via Vapor-Phase Deposition

Porous polymer materials are desired for a variety of applications such as catalysis, filtration, sensing, optics, and biological engineering. In this work, we present a modified initiated chemical vapor deposition (iCVD) process to synthesize spongelike stimuli-responsive poly(methacrylic acid) (PMAA) polymer coatings and freestanding films characterized by micron-sized pores, pore interconnectivity, and varying heights. The carboxylic acid functional group in the PMAA sponge allows for pH-responsive behavior ideal for biomedical applications and separations. Thermal annealing was used to control the dissolution of sponge coatings in different pH environments. Ethylene glycol diacrylate was introduced during the fabrication process to form freestanding sponges with pH-responsive swelling behavior, and glycidyl methacrylate was introduced during the fabrication process to increase the durability of sponge coatings. Hierarchical structures with a bottom sponge layer and a top pillared layer were fabricated in situ by varying processing conditions. The sponge structures were coated with a fluorinated polymer to fabricate superhydrophobic structures with self-cleaning properties. Our fabrication process offers an all-dry one-pot method to synthesize polymer sponges with different functionalities for a range of applications in drug delivery, sensor, and separation applications.