Self-Assembly of Trimesic Acid at the Liquid−Solid Interfacea Study of Solvent-Induced Polymorphism

• Published in: Langmuir 2005-05, Vol.21 (11), p.4984-4988
• Main Authors: Lackinger, Markus, Griessl, Stefan, Heckl, Wolfgang M, Hietschold, Michael, Flynn, George W
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Surface physical chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la0467640

A scanning tunneling microscope operated under ambient conditions was utilized to study the self-assembly of trimesic acid (TMA) at the liquid−solid interface. On a graphite substrate, two different open, loosely packed, two-dimensional hydrogen-bond networks were found. Both structures exhibit a periodic arrangement of ∼1.0 nm wide cavities, which can be used for the co-adsorption of another species (guest) within the cells of this host system. These two polymorphs (“chickenwire” and “flower” structures) differ in their molecular packing density and hydrogen-bonding schemes. Using a homologous series of alkanoic acids as solvents, ranging from butyric to nonanoic, selective self-assembly of either the “flower” or “chickenwire” forms was achieved on a graphite surface. Solubility of TMA in these acid solvents was found to decrease with increasing chain length, and the longer-chain solvents favored formation of the chickenwire polymorph structure on the surface.