Responsive Surfaces Prepared from Triblock Copolymer Brushes

Atom-transfer radical polymerization (ATRP) is a "living" polymerization technique that allows facile synthesis of multi-block copolymers. Because polymerization sites have long lifetimes, one can isolate polymer chains, transfer them to a solution of a different monomer, and grow a second block from the terminus of the first block. Using our recently developed methods for room-temperature ATRP from a surface, we prepared the first triblock copolymer brushes. Judicious selection of blocks with regard to their hydrophobicity results in surfaces that phase segregate into patterns upon exposure to specific solvents as shown for methylene chloride (top image) and methanol (bottom image). The characteristic size of the domains are 45 nm, much smaller than the 110 nm reported for diblock brushes. Such patterns are potentially useful in preparing nanostructured devices.