Fabrication of Adhesive Polymer Films via Nanoimprint Lithography and Surface‐Initiated <scp>ATRP</scp> : Synergistic Effect of Vertically Aligned Pillars and Electrostatic Interactions

ABSTRACT Vertically aligned nanopillar structures offer unique opportunities for enhancing interfacial adhesion by combining surface morphology with chemical functionality. Herein, we report the fabrication of hierarchically structured polymer films bearing nanopillar arrays grafted with oppositely charged polymer brushes via surface‐initiated atom transfer radical polymerization (SI‐ATRP). A copolymer containing photo‐crosslinkable cinnamoyl groups and ATRP initiation sites was nanoimprinted on Si substrates to form nanopillar films, which were subsequently stabilized by photocrosslinking. Positively charged poly(2‐(methacryloyloxy)ethyl trimethylammonium chloride) (poly( MTAC )) and negatively charged poly(3‐sulfopropyl methacrylate potassium salt) (poly( SPMK )) were selectively grafted from the nanopillar surfaces using SI‐ATRP. When oppositely charged nanopillar films were brought into contact in the presence of a small amount of water, strong adhesion was achieved through electrostatic interactions between the grafted polymers. Lap shear tests revealed an adhesion strength of 120 ± 20 N cm −2 , which is more than an order of magnitude higher than that of similarly grafted smooth films, despite comparable surface charge densities. In contrast, ungrafted nanopillar films showed no adhesion. These results demonstrate that the synergistic combination of SI‐ATRP‐derived polyelectrolyte brushes and nanopillar surface architecture enables highly efficient adhesive interfaces, providing a versatile strategy for designing advanced functional adhesive materials.