Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface

Abstract

Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface Abstract: Calamitic (rod-shaped) and discotic (disc-shaped) thermotropic liquid crystalline (LC) compounds were spread at the air-water interface, and their ability to form monolayers was studied. The calamitic LCs investigated were found to form monolayers which behave analogously to conventional amphiphiles such as fatty acids. The spreading of the discotic LCs produced monolayers as well, but with a behaviour different from classical amphiphiles. The areas occupied per molecule are too small to allow the contact of all hydrophilic groups with the water surface and the packing of all hydrophobic chains. Various molecular arrangements of the discotics at the water surface to fit the spreading data are discussed. U n i v e r s i t ä t P o t s d a m

Spectral properties of naphthalimide dyes mixed with 4-heptyl-4′-cyanobiphenyl (7CB) in Langmuir-Blodgett films

“…In some cases, behind the col− lapse point a broad plateau region is observed, however, with the different surface pressure value, while in the others, the pressure rises monotonically with a decrease in the available area. However, the shapes of all p−A isotherms obtained for dyes 1−12 were similar to those which can be found in litera− ture for other compounds [1][2][3]11,[14][15][16][17][18]. No significant dif− ferences in the isotherms runs during compression and expan− sion processes were observed meaning that the monolayers formed were stable.…”

A Structural Study of Amphiphilic PAMAM (Poly(amido amine)) Dendrimers in Langmuir and Langmuir–Blodgett Films

“…Hence, structural studies of Langmuir and L-B films are always important and useful in the surface chemistry (1)(2)(3)(4)(5)(6)(7)(8). Face-on and edge-on models (3)(4)(5) are most commonly used to describe the orientation of those molecules in Langmuir and Langmuir-Blodgett films. The studies on the factors regulating the molecular orientation in Langmuir and L-B films have become an important research topic for the edge-on model.…”

Unexpected Square Symmetry Seen by Atomic Force Microscopy in Bilayer Films of Disk-Like Molecules

“…and LB films (5,6). The electronic conduc-Although most research in this area has tivity of doped bulk discotic mesophases is, concentrated on LB films of amphiphilic highly anisotropic, with most of the conduc-SCIENCE VOL.…”

“…Surface pressure versus molecular area (11-A) measurements of Langmuir films of discogenic molecules (4,6) indicate that discotic mesogens can adopt two possible types of packing at the air-water interface. Large, flexible cores with long substituents and highly polar anchor groups can drive molecules to sit with the cores parallel ("face-on") to the interface.…”