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A reorientation phenomenon that takes place inside confined smectic-C (SmC) domains in a phase-segregated Langmuir film is reported. The process involves a sign reversal of the splay texture following the transient displacement of the central defect.

In a photoresponsive Langmuir monolayer comprised of smectic-C-like domains of mesogenic trans-azobenzene derivative embedded within an isotropic matrix of its cis isomer counterpart, several structurally differing circular droplets were irradiated with linearly polarized light. This report describes the structural rearrangements that occurred in these droplets upon illumination followed by Brewster angle microscopy analysis. Starting from initial well-characterized and symmetric states, final photoaligned situations were reached in which the azimuth angles of the rod-shaped elongated molecules were found to be perpendicular to the electric component of the excitation light. The dynamical aspects of the photoalignments, including their transient patterns, are captured by a theoretical model that couples a relaxational principle incorporating long-range elastic forces with a kinetic formalism presenting an anisotropic rate law. [ABSTRACT FROM AUTHOR]

An experimental phenomenon of collective light-induced reoriental processes at the air or water interface is described. The way in which a cycle of weak on/off linearly polarized illumination can totally reverse the radially symmetric pattern of orientations of stretched amphiphilic molecules assembled in condensed smectic-C-like droplets in a Langmuir monolayer is demonstrated.

The article focuses on a study related to photoswitchable orientational patterns of confined domains in monolayers. Soft materials prepared from supramolecular or self-assembling strategies provide researchers with a diversity of potential technological benefits. Leaving aside obvious implications for the design of sensors and devices, model cooperative molecular systems may provide the means to unveil how noncovalent interactions in complex chemical systems can lead to the emergence of adaptive and collective responses to external stimuli.