Phase transitions of amphiphiles at the air-water interface under compression
Amphiphilic molecules (phospholipids, fatty acids) have hydrophilic heads and hydrophobic tails. At the air-water interface they form Langmuir monolayers. Compression reduces area per molecule A, driving phase transitions: gas → liquid-expanded (LE) → liquid-condensed (LC) → solid. The π-A isotherm is measured and the shape depends on temperature.