Langmuir films of bent-core molecules at the air/water interface are transferred onto a solid surface by the inverse-Langmuir-Schaefer (ILS) technique. Previous work by the authors demonstrated that ILS films of a symmetric bent-core molecule can serve as effective planar alignment layers for a nematic bent-core liquid crystal cell, but the Langmuir films were unstable and formed multilayers at very low pressures. Here, films of bent-core molecules with one hydrophilic end connected to the bent core by a short aliphatic chain are tested as alignment layers. The hydrophilic group led to much more stable Langmuir films, and also to a molecular tilt at the surface which could be controlled by molecular area. This interpretation of the molecular behavior was supported by a combination of atomically accurate molecular dynamics simulations of up to 36 bent core molecules at a water surface and by the continuous variation of tilt induced by ILS films in a rod-like liquid crystal cell. The ILS films were then tested as alignment layers for a bent-core nematic: highly-compressed films induced perpendicular alignment, which provides a significant step towards their practical application.
Available on publisher's site at http://dx.doi.org/10.1039/c1sm05546a.
Iglesias, Wilder; Smith, Timothy J.; Basnet, Prem B.; Tschierske, Carsten; Lacks, Daniel J.; Jakli, Antal; Mann, Elizabeth K. (2011). Alignment by Langmuir/Schaefer Monolayers of Bent-Core Liquid Crystals. Soft Matter 7(19) 9043-9050. doi: 10.1039/c1sm05546a. Retrieved from https://oaks.kent.edu/cpippubs/333