Do crowded phospholipid monolayers remain fluid?

Abstract Phase separation in mixed lipid layers is used here to mimic crowding at interfaces, providing insights into the dynamics of (and within) phospholipid monolayers. The interface is fully fluid at temperatures above the liquid-condensed (LC) phase melting point for the range of accessible interfacial pressures. Upon cooling, temperature-induced phase separation occurs. We moreover control the solid-like LC phase fraction by tuning the lipid composition between dipalmitoyl-phosphatidylchol