Molecular dynamics simulation of phase transitions in model lung surfactant monolayers

► Molecular dynamics simulation of liquid-condensed-liquid-expanded phase transitions. ► Liquid-condensed phase forms via nucleation and growth. ► Disordering transition occurs by melting originating at defects. ► SP-B1-25 aggregates in the liquid-expanded phase and nucleates disorder in the monolayer. ► Cholesterol displays a preference for the interface between the ordered and disordered phases.