Controlling thread assemblies of pharmaceutical compounds in liquid crystal phase by using functionalized nanotopography

The ability to control the organization of molecules in different aggregates is important for the fundamental understanding of polymorphism and for engineering desired pharmaceutical properties of drug molecules such as bioavailability, stability, and non-toxicity. Here, we describe the control of the molecular assembly of two hydrated molecules in liquid crystal phases (so-called chromonic liquid crystals) uniformly over long distances. The two molecules include an antiallergy drug, disodium cromoglycate (5DSCG), and a dye molecule, Sunset Yellow (SY dye). The surfaces consist of self-assembled monolayers (SAMs) of functionalized alkanethiols supported on gold films that were prepared by deposition of gold onto glass slides at an incident angle oblique from the surface normal of the glass slides. Hydrated molecular threads of 5DSCG and SY dye aligned parallel to the surface of the SAMs and uniformly over the large surface area. The azimuthal direction of the uniform alignment was either parallel or perpendicular to the direction of gold deposition depending on whether the total number of skeletal atoms (non-hydrogen), p, is odd or even in the SAMs composed of a variety of functional groups, including methyl, hydroxyl, or tri(ethylene glycol). When two SAMs differing in one methylene unit (-CH₂-) in the aliphatic chains (for example, HS(CH₂)₁₁(OCH₂CH₂)₃OH and HS(CH₂)₁₂(OCH₂CH₂)₃OH) were supported on each gold film of the optical cell, the odd-even effect creates a twisted assembly of the molecular hydrates between the surfaces. Considering the high percentage of water in the hydrate studied (∼70 to 88 wt %), this surface approach has the potential to provide a powerful way to influence the molecular arrangement in general for other solvates or hydrates.