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 laura te have been studied at different temperatures. Domains in these monolayers are not observed at greater than or equal to 26 degreesC, 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 c ircular to fingering pattern near 15 degreesC. The domains have more branch ing in their structures with a further increase in the temperature. Increas ed formation rate by a temperature jump causes fractal domains at greater t han or equal to 15 degreesC but does not change the domain shapes at lower temperatures. The fractal structures formed by a high growth rate undergo r elaxation to their equilibrium shapes within 25 min. A continuous variation in the textures of the domains with temperature is observed. Similar to th e shape transition, above 13 degreesC the domains show a transition from st ripe texture to one of uniform molecular orientation. Below this temperatur e, the width of the stripes formed reduces with decreasing temperature. At 13 degreesC, the texture is either absent or present as a special fingering in the stripes.