Self-assembly of functional host-guest structures at interfaces

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Intellectual Merit:Surface functionalization the ability to alter the chemical or biological properties of a solid substrate is now an important component in a number of technical fields, including chemical separations, sensing, catalysis, and bioengineering. The simplest means of adding functionality to a surface is the physical adsorption of functional molecules with little or no control over the thickness of the resulting film or the final orientation and position of the functional groups with respect to the surface. In contrast, Langmuir-Blodgett (LB) film deposition allows precise control over film thickness and also provides for consistent orientation and positioning of the functional groups. Self-assembled monolayers (SAMs) also result in the creation of a densely packed monolayer film with the added benefit of stronger interactions between the monolayer and the solid substrate. The disadvantage to both of these techniques is that they require the synthesis of molecules with the desired functional group at one end and either a hydrophilic headgroup (LB film) or reactive group (SAM) at the other end. This á−ù synthesis is time consuming and limits the number of functional surfaces that can be created. These methods can be simplified and improved by borrowing concepts from 3-D crystal engineering, specifically those of host guest inclusion compounds. The PI has demonstrated the creation of ternary host-guest monolayers at the air water interface based on hydrogen bonding between alkanesulfonate amphiphiles and guanidinium ?spacer? counter-ions which form cavities into which a variety of alkyl substituted functional guest molecules can be inserted. These host-guest monolayers can be transferred to solid substrates via LB deposition in order to form functionalized surfaces. The proposed work has the capacity to transform current methods of surface functionalization by opening up a large library of functionalized surfaces that can be formed using a common host monolayer system into which can be inserted a multitude of alkyl substituted guest molecules.The nano-related project is broken down into three sections: 1) characterization of host-guest LB films based on guanidinium sulfonate host monolayers, including film stability, and the kinetics of insertion and exchange of commercially available homologous guest molecules; 2) synthesis and characterization of host-guest LB films based on sterically hindered amphiphiles amphiphiles possessing an integral ?spacer? moiety; and 3) synthesis and characterization of analogous sterically hindered host-guest SAM films that are strongly bound to the solid substrate, providing greater stability and allowing the functionalization of non-planar substrates such as 3D scaffolds and nanoparticles.Broader Impacts:The nano-related project has the potential to benefit society by enabling the production of materials and devices with tailored surface functionality, with applications in sensing,biocompatibility, separations, and catalysis. This research will also advance discovery, while promoting teaching and learning at the high school, undergraduate, and graduate levels by providing: (1) research opportunities for undergraduate students, including underrepresented minorities and women during both the regular academic year and in a summer research program and their participation in outreach programs to encourage high school students, particularly women, to pursue careers in engineering; (2) coordinated recruitment of graduate students from under-represented groups with Virginia Tech?s Office of Graduate Student Recruiting into an interdisciplinary research program and their participation in outreach programs such as C-Tech2and opportunity to mentor undergraduate researchers, and (3) the inclusion of knowledge and examples drawn from this work in my elective Self-Assembly course and our undergraduate Unit Operations laboratory course. The results of this research will be widely disseminated to the scientific and lay communities in peer-reviewed journals, in presentations at multi-disciplinary conferences, in undergraduate symposia, and in course web pages.