Polymer Brush Morphology-Directed Orientation and Arrangement of Gold Nanorod Arrays

Polymer brush–gold nanoparticle (AuNP) hybrids have attracted considerable attention because the structural flexibility of polymer brushes complements the geometry-dependent plasmonic properties of AuNPs. When AuNPs are brought into close proximity, coupling between their localized surface plasmon resonance (LSPR) modes alters their electronic and optical characteristics, enabling the design of tunable plasmonic materials. Among various hybrid systems, precise control over the plasmonic responses of anisotropic AuNPs such as gold nanorods (AuNRs) remains challenging due to their increased structural and orientation-dependent complexity. Integrating AuNRs with polymer brushes offers additional tunability arising from the anisotropic shape of the nanorods, including orientation- and arrangement-dependent optical behavior. In this study, we demonstrate plasmonic modulation of AuNRs through structural regulation of poly(styrenesulfonate) (PSS) brushes. Drastic yet reversible orientation changes of AuNRs were achieved by compressing the PSS brushes using poor solvents. Furthermore, distinct plasmonic responses were observed depending on the assembled structures of tilted AuNRs within the brushes, reflecting different morphological states of the brush matrix under external stimuli. The brush–nanorod hybrids, which enable controllable orientation and assembly of AuNRs, exhibit tunable optical properties and hold promise for applications in colorimetric, optoelectronic, and plasmonic devices.