EFFECT OF CHAIN CONFORMATION ON THE TILT BEHAVIOR IN LANGMUIR MONOLAYERS

Monolayers of amphiphilic molecules at the air-water interface exhibit a phase transition from a state in which the molecules are normal to the interface to one in which they are tilted. Molecular-dynamics simu lations have been used to investigate the relation between chain confo rmation and tilt transition, and the effect of temperature thereupon. Results show that a decrease in temperature induces an increase in til t angle and conformational order. Monolayers at 275 and 300 K undergo a clear tilt transition at approximately 0.20 mm2/molecule. At high de nsity, the tilt behaviour at equilibrium and during relaxation is coup led to the formation of gauche defects.