The self-assembly of metallic nanoparticles into largescale ordered structures offers a promising avenue for the manufacturing of optical devices and photonic elements. Herein, we demonstrate that largescale, highly uniform thin films of polystyrene-grafted gold nanorods (PGNRs) can be fabricated within seconds by applying a simple flow-coating technique. Using autonomous small-angle x-ray (SAXS) measurements, we efficiently explore the processing parameter space on thin films cast with orthogonal surface energy and deposition velocity (v) gradients. Agreeing with theoretical predications, we find that film thickness scales as v<sup>-1</sup> or v<sup>2/3</sup> when processing in the evaporative regime or Landau-Levich regime, respectively. Additionally, we observe positional and orientational order dependent on coupling between surface energy, process methodology, and the architecture of the grafted polymer canopy. We show that globally oriented films possessing two-dimensional orientation parameters greater than 0.7 can be achieved through evaporation induced-assembly when processing in the evaporative regime on hydrophilic surfaces. Optical characterization was performed using a combination of variable angle spectroscopic ellipsometry and optical extinction measurements. Strong plasmonic coupling between the gold nanorods is revealed which can systematically be tuned between narrow and broadband extinction in the NIR by simply varying film morphology for a single PGNR sample. With fundamental understanding of structure-processing relationships, further tuning of the optical properties is demonstrated by systematically changing molecular weight of the polymer graft and nanorod shape.

Ordered assemblies of polymer-grafted gold nanorods and their optical properties

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.