Foulant Adsorption to Heterogeneous Surfaces with Zwitterionic Nanoscale Domains

Heterogeneous materials with alternating hydrophobic and hydrophilic domains have challenged the long-standing paradigm that surfaces with higher hydrophilicity are more effective at resisting foulant adsorption. This work probes the underlying mechanisms for the observed phenomenon by exploring the effect of domain size, domain contrast, and foulant properties on adsorption to heterogeneous surfaces. We fabricate chemically heterogeneous surfaces from random zwitterionic copolymers of varied composition that phase-segregate at low weight percent to yield equivalently sized hydrophilic domains. We systematically vary the hydrophobic domain size by changing the weight percent of the zwitterionic monomer and the domain contrast by changing the hydrophobic monomer. We investigate the adsorption of heterogeneous and homogeneous foulants to these surfaces, as well as to control surfaces of uniformly blended hydrophilic and hydrophobic polymers. We find that hydrophilicity is a poor predictor of protein and heterogeneous macromolecular adsorption to chemically heterogeneous surfaces. Instead, adsorption is primarily determined by the local interaction energy between the foulant and surface domains and is inhibited when the length scale of foulant anchoring sites is larger than the length scale of the surface domains. These observations do not hold for chemically homogeneous macromolecules, where the adsorption is strongly correlated with average interaction energy and surface hydrophilicity.