Structural characterization of crystalline ternary inclusion compounds at the air-water interface

This thesis explores crystalline ternary inclusion Langmuir monolayers at the air-water interface in which the stabilizing host monolayer was based on the two-dimensional hydrogen-bonded network created by guanidinium ions (G) and the sulfonate (S) moieties of organosulfonate amphiphiles. Grazing-angle incidence X-ray diffraction of the crystalline monolayers revealed that the ability to sustain ternary host-guest monolayers with the GS network intact appears to require guests that are structurally homologous, in the strictest sense, with the organosulfonate substituents. Nonetheless, the observation of these inclusion compounds suggests an approach for the design and synthesis of functional monolayers in which non-amphiphilic molecules adorned with desired functionality could be anchored at the air-water interface through intercalation in host inclusion cavities with well-defined metrics. Such an approach offers the prospect of separating the function of the guest from the inherent structure of the host, avoiding the requirement of designing functional molecules that are also amphiphilic.; This thesis also describes an approach for the rational screening of Langmuir monolayers capable of selective nucleation of organic polymorphs. Polymorph selectivity has been demonstrated to be achieved through an epitaxial match of an overlayer on a properly chosen solid substrate. This approach may be extended to polymorph crystallization from an aqueous subphase beneath a Langmuir monolayer. For our purposes, the overlayer is equivalent to the Miller plane of a crystal polymorph nucleating from the aqueous subphase and the substrate is the bottom face of a crystalline monolayer.