Pore-selective modification of the honeycomb-patterned porous polystyrene film with poly(N-isopropylacrylamide) and application for thermo-responsive smart material

Porous honeycomb-patterned (HCP) polystyrene (PS) film was pore-selectively functionalized by carboxylic acid group and modified by thermo-responsive poly (N-isopropylacrylamide) (PNIPAAm) to extend the application of HCP polymer films. The carboxylic acid functionalized film was obtained by a reactive breath figure method by casting a formylated PS (PS-CHO) solution under aqueous humid conditions containing oxone, which oxidized aldehyde into carboxyl acid at the interface of a water droplet/polymer solution accompanying an interfacial reaction. The fabricated film was reacted with amine-terminated poly (N-isopropylacrylamide) in aqueous solution for the pore-selective PNIPAAm modified HCP film. Temperature-dependent pore-surface morphology and wettability of the film were observed by scanning electron microscopy and contact angle measurement analysis after immersing into the water at below and above the lower critical solution temperature of PNIPAAm. The increase of temperature induced the pore-surfaces of the film to a higher rugged surface morphology and more hydrophobicity. The temperature-dependent capture ability of Ag nanoparticles in the pore-selective PNIPAAm modified HCP film was studied by immersing the film in aqueous solution containing Ag nanoparticles at 25 °C and 40 °C, which resulted in a higher capturing at higher temperature.