Mesoporous Block Copolymer Nanorods by Swelling-Induced Morphology Reconstruction

Engineering the topography of thin block copolymer (BCP) films by surface reconstruction associated with selective swelling of one of the blocks has been investigated intensively. Here we show that swelling-induced structural transitions in nanorods consisting of amphiphilic BCPs involve pronounced reshaping of the nonswollen glassy domains in the course of the transition from the equilibrium morphology of the molten BCP in cylindrical confinement to that of the BCP dissolved in the swelling agent. The reconstruction process can be quenched to retain intermediate nonequilibrium morphologies. The collapse of the swollen chains upon drying yields polymeric nanorods exhibiting complex nanoscopic architectures characterized by a variety of mesopore structures and surface topographies, including channels along the nanorods, bunches of partially interconnected strands, and strings of spheres. The complex BCP nanorods thus obtained can be used as soft templates for the rational arrangement of metal nanoparticles.