LIQUID-CRYSTALLINE TEXTURE IN GLYCINE-MODIFIED DIACETYLENE LANGMUIR MONOLAYERS AT ROOM-TEMPERATURE

Direct visualization of the self-assembling and liquid crystalline texture formation in glycine-modified diacetylene (Gly-DA) Langmuir monolayers at room temperature is achieved using Brewster angle microscopy (BAM). The striped (smectic) texture appears directly after spreading the monolayer at the air-water interface. The spatial period of this texture has been estimated to be in the range 0.015-0.005 mm, which is in agreement with the range predicted theoretically for this phase. When pressure is applied, the width of the strips decreases and, finally, the striped texture disappears. Another texture appears in the pressure range 30-35 mN/m: the well-defined pseudo-focal-conic texture, which points to a disordered hexagonal columnar mesophase. In addition, direct visualization of the Gly-DA polymerization under UV radiation exposure via BAM is achieved. We observe focal-conic texture reminiscent of smectic C phase.