Controlled Gold Nanorod Reorientation and Hexagonal Order in Micromolded Gold NanorodNIPAM Microgel Chain Arrays

A one-step soft lithography based pathway to manufacture aligned gold nanorodoly-(N-isopropylacrylamide) (GNRNIPAM) hybrid chains with hexagonal arrangement of the nanorods and with an anisotropic optical response is presented. After demonstration of an efficient synthesis protocol, yielding uniform composite microgels in high concentration, a micromolding procedure using wrinkled polydimethylsiloxane (PDMS) templates to fabricate aligned hybrid chains is introduced. It is found that the self-assembled GNRNIPAM microgels inside the PDMS wrinkle grooves can be transferred onto solid substrates, on which they exhibit a hexagonal order, as confirmed by small-angle X-ray scattering. Further, it is shown that the application of minimized PDMS wrinkle dimensions aligns GNRs inside the pNIPAM microgels, and that the optical response of such molded assemblies is anisotropic. Gold nanorodoly-(N-isopropylacrylamide) hybrid microgels are assembled into periodically aligned chains, exhibiting a hexagonal structure and anisotropic optical response. The manufacturing process involves a micromolding procedure providing ordered large-scale transfer of hybrid microgels onto solid substrates. A hexagonal arrangement was found from small-angle X-ray scattering. Mechanical confinement enables global control of gold nanorod orientation causing optical anisotropy.