Relationship between the ability to control liquid crystal alignment and wetting properties of calix[4]resorcinarene monolayers

Abstract

This paper describes the correlation between the ability to control nematic liquid crystal (LC) alignment and wetting properties of mixed monolayers formed by coadsorption of two O-octacarboxymethylated calix[4]resorcinarenes (CRA-CMs) with either perfluorooctyl-or octylazobenzene units. Photoirradiation of CRA-CM monolayers induces reversible photoisomerization reaction of the surface azobenzenes, which causes changes in LC alignment and wettability of the monolayers. The photogenerated LC alignments are considerably influenced by the surface compositions of the mixed monolayers. When LC cells fabricated with substrate plates modified with single-component monolayers of CRA-CM with p-octylazobenzenes are subjected to oblique irradiation with non-polarized UV light, the orientation of LC molecules is changed from homeotropic to homogeneous alignments tilting toward the direction of light propagation. In contrast, singlecomponent and mixed monolayers of CRA-CM with p-perfluorooctylazobenzenes cause homeotropic alignments and tilted alignments with high pretilt angles, respectively. The level of photoisomerization and surface free energy of the CRA-CM monolayers are not a sufficient condition to cause the contrasting alignment behaviors. We conclude that the molecular-level morphology and/or fluidity of the monolayer surfaces of CRA-CMs, which is deduced from the contact angle hysteresis of anisotropic liquids for the surfaces, is the most significant factor to induce the LC alignment alterations observed.

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

“…It has been known that the high pretilt angles of LC molecules required to produce homeotropic alignment are related to the low surface energy values of the alignment layer and/ or the steric repulsions between the LC molecules and the alignment layers. 36,[49][50][51][52][53][54][55][56] Therefore, polyimides having long alkyl side groups have been widely used to align LCs perpendicular to the surface of the alignment layer, because the long alkyl groups can produce low surface energy layers due to their steric effect. 51,56 We also found that the LC alignment behavior on the polystyrene derivatives in this study could be ascribed to the surface energy values.…”

Fabrication of New Liquid Crystal Device Using Layer-by-Layer Thin Film Process

“…These results indicated the creation of uniform homeotropic LC alignment on the LBL thin film electrode; the number of BLs did not disturb the vertical alignment of the nematic LCs in the device. In addition, typical conoscopic images of the VA LCDs are shown in the insets of Figure 5 [34,35]. The conoscopic images showed a distinct Maltese cross, which indicates the vertical alignment of the LC molecules.…”

Synthesis and Conformational Properties of Partially Alkylated Methylene‐Bridged Resorc[4]arenes – Study of the “Flip‐Flop” Inversion

“…Thus, we can find resorcinarenes as parts of carceplexes, hemicarceplexes, [9][10][11] dendrimers, [12][13][14] and other supramolecular entities. [15][16] The binding properties of resorcinarenes can be significantly influenced by their stereochemistry. In theory, resorcinarenes can exist in several isomeric forms named crown (cone), boat (pinched cone), chair (flattened partial cone), diamond (1,2-alternate) and saddle (1,3-alternate) (Figure 1).…”