In this review, we focus on the role of surface heterogeneity in polymer adsorption and discuss novel experiments that clarify the impact of topographical and chemical heterogeneity on adsorption of flexible polymers and globular proteins. The comparison of the experimental results with existing theoretical predictions provides valuable insights into the adsorption process and guides future development of theory and experiments. Furthermore, these results provide a starting point for more sophisticated design and control of polymer adsorption at the nanoscale and in engineering of surfaces to achieve specific tasks.

The importance of polymer and protein adsorption stems from its critical role in a host of industrial applications such as adhesion, biocompatibility, colloidal stabilization, and chromatography. Scientifically, the interfacial behavior of globular proteins and long, flexible macromolecules and the accompanying balance of enthalpic and entropic effects from surface-segment interactions provide a system replete with interesting static and dynamic phenomena. Consequently, adsorption of polymers and biopolymers at a solid-liquid interface has been the subject of intense investigation over the last decade.

Despite the advances in characterization and theoretical understanding of near-equilibrium properties of adsorbed polymer layers, several aspects of the adsorption process remain elusive.1-31, 2, 3 Among these elusive aspects is the effect of nanometer scale compositional and topographical heterogeneity of surfaces (Fig. 1a) on the process of adsorption and the structural properties of the adsorbed layer. Because adsorption frequently occurs on real surfaces such as minerals, pigments, colloidal particles, and biological membranes that are inherently heterogeneous, understanding the impact of surface heterogeneity is an essential prerequisite to controlling the adsorption process. Fig. 1. Schematic of (a) a heterogeneous surface and (b) evolution of the surface excess (Γ).