Hydrogen-bonded polymer nanocomposites containing discrete layers of gold nanoparticles

The ability to finely control the spatial location and relative concentration of a nanofiller within a polymer nanocomposite is desirable, especially when faced with fillers that are susceptible to aggregation. In the case of gold nanoparticles (AuNPs), spatial organization is of interest as it offers a means to harness optical and electrical properties, but well-defined placement of AuNPs within a polymer matrix is generally challenging because of phase separation. Here, we demonstrate for the first time the spray-assisted layer-by-layer assembly (LbL) of hydrogen-bonding polymer nanocomposites of poly(ethylene oxide) (PEO) and poly(methacrylic acid) (PMAA) containing discrete regions of AuNPs vertically positioned throughout the film structure. Analysis of the internal structure using cross-sectional transmission electron microscopy (TEM) imaging shows that the AuNP regions are clearly separated by "empty" regions of polymer with no drift or aggregation of the Au NPs during or after fabrication. A UV-vis spectroscopy study of the stimuli-responsive properties of the spray-assisted LbL nanocomposites shows the release of AuNPs as induced by elevating the environmental pH above the critical pH at which the PEO and PMAA hydrogen bonds are disrupted. We anticipate that this work enables the spatial organization of other nanofillers in stimuli-responsive hydrogen-bonding nanocomposites by spray-assisted LbL assembly.