Fabrication of Stimulus-Responsive Nanopatterned Polymer Brushes by Scanning-Probe Lithography

Stimulus-responsive, surface confined poly(N-isopropylacrylamide) (pNIPAAM) brush nanopatterns were prepared on gold-coated silicon substrates in a "grafting-from" approach that combines "nanoshaving", a scanning probe lithography method, with surface-initiated polymerization using atom transfer radical polymerization (ATRP). The reversible, stimulus-responsive conformational height change of these nanopatterned polymer brushes was demonstrated by inverse transition cycling in water, and water-methanol mixtures (1:1, v:v). Our findings are consistent with the behavior of laterally confined and covalently attached polymer chains, where chain mobility is restricted largely to the out-of-plane direction. Our nanofabrication approach is generic and can likely be extended to a wide range of vinyl monomers.