A Novel Optical Absorption Method to Monitor Polymer Infiltration Inside a Bicontinuous, Nanoporous Gold Scaffold

Polymer nanocomposites (PNC) have received much attention due to their wide ranging applications from tires to membranes. Creating PNCs with high loading remains a challenge because discrete nanoparticles tend to aggregate. In this work, we create high loading PNCs by fabricating polymer infiltrated nanoporous gold (PING). Ultraviolet-visible (UV-Vis) spectroscopy is used to monitor polymer infiltration in nanoporous gold (NPG). In this study, poly(2-vinylpyridine) (P2VP) is infiltrated into NPG that has a bicontinuous structure with ca. 50 vol% porosity and 75 nm pore diameter. Upon heating above its glass transition temperature, P2VP infiltrates inside the NPG, resulting in a plasmon resonance peak wavelength shift and absorption intensity increase. Simulations using discrete dipole approximation are employed to validate the accuracy and efficacy of UV-Vis spectroscopy in examining the PING formation. Infiltration time scales with molecular weight as M1.4, in agreement with previous spectroscopic ellipsometry findings. These studies provide a new fundamental understanding of polymer melt infiltration under confining conditions as well as guidelines for fabricating PNCs with loadings above 50 vol%.