Line Tension Induced Instability of Condensed Domains Formed in Adsorbed Monolayers at the Air−Water Interface

The morphological features and textures in condensed domains formed during first-order phase transition in adsorbed monolayers of 2-hydroxyethyl laurate have been studied at different temperatures. Domains in these monolayers are not observed at ≥26 °C, indicating that the critical temperature for the phase transition is near this value. Under equilibrium conditions, the shapes of the domains show a transition from circular to fingering pattern near 15 °C. The domains have more branching in their structures with a further increase in the temperature. Increased formation rate by a temperature jump causes fractal domains at ≥15 °C but does not change the domain shapes at lower temperatures. The fractal structures formed by a high growth rate undergo relaxation to their equilibrium shapes within 25 min. A continuous variation in the textures of the domains with temperature is observed. Similar to the shape transition, above 13 °C the domains show a transition from stripe texture to one of uniform molecular orientation. Below this temperature, the width of the stripes formed reduces with decreasing temperature. At 13 °C, the texture is either absent or present as a special fingering in the stripes.