Two-dimensional domain shape transitions in photosensitive monolayer assemblies

Bubble-stripe shape transitions of gaseous domains are observed in Langmuir monolayers of porphyrin/arachidic acid and porphyrin/spiropyran mixtures using fluorescence microscopy. Characteristics of the transition such as critical bubble size are found to be controllable by subphase pH or UV/visible irradiation. These features are discussed in terms of a balance between dipolar repulsions and line tension in the monolayer.