COLLOIDAL GOLD DISPERSIONS IN POLYMERIC MATRICES

We have studied the distributions of colloidal gold particles in poly(2-vinylpyridine) (PVP), at the surfaces of polystyrene (PS) and PVP, and at the interface between PS and PVP. Small (d = 20 nm) gold particles were deposited onto PS or PVP surfaces by adsorption from an aqueous colloidal gold suspension. The resultant gold distributions were characterized by transmission electron microscopy, Rutherford backscattering spectrometry, scanning force microscopy, and X-ray photoelectron spectroscopy. Contrary to the results obtained for PS surfaces, the particles adsorb strongly to poly(2-vinylpyridine) surfaces to form stable two-dimensional dispersions, even at temperatures at which the gold particles are quite mobile. The particles remain at the PVP surface during a high temperature treatment, consistent with our finding that the contact angle of PVP on an evaporated gold layer is finite (9 ± 1°). The gold particles are free to diffuse within a bulk PVP phase, where a quantitative measure of the gold particle dilfesion coefficient at 179°C is obtained. We also find that a certain fraction of the gold particles are trapped at the interface between PS and PVP, a result which we relate to the dynamics of polymer chains at the gold surfaces. The relationship between the behavior of the colloidal gold dispersions in polymer matrices and the fundamental process of segmental exchange at a polymer/solid surface is discussed. © 1993 Academic Press, Inc.