Mesoscopic, two -dimensional self -assembly: Molecule -mimetic chemistry

This thesis describes the study of mesoscopic, two-dimensional self-assembly of poly(dimethylsiloxane) (PDMS) objects at the fluid-fluid (perfluorodecalin(PDF)-water) interface. The work uses the concepts that form the basis of molecular self-assembly---shape-, size-, and sequence-selective recognition between different objects with complementary surfaces, attraction between hydrophobic regions, ligand/receptor interactions, hierarchical interactions, DNA/DNA interactions, and templated self-assembly---in a new way. Lateral capillary interactions can hold mm-sized objects in contacts that are sufficiently strong to withstand modest shear. The hydrophobic faces have large, positive menisci (the maximum height of the menisci is approximately the height of the faces for the objects we have used); these faces are strongly attracted to one another. The hydrophilic faces have small, negative menisci (the maximum height of the menisci is < 40 % of the height of the faces); these faces are weakly attracted to one another. Faces having positive menisci are repelled by faces having negative menisci. The work uses molecular chemistry at surfaces to control menisci and hence interactions: the work has a strong chemical component, but extends from molecular interactions to interactions at surfaces and between materials and then to meso-scale objects. The work points to a new way of fabricating and assembling small, non-molecular components using self-assembly and provides a macroscopic experimental model for molecular recognition that matches some aspects of the abstract lattice models used in statistical mechanical treatments of molecular phenomena.;Chapter 1 describes the system that used "receptors" and "ligands", fabricated as complementary shapes by joining small hexagonal PDMS plates and suspended at a PDF water interface. Receptors showed excellent selectivity for ligands based on complementarity of shape and juxtaposed hydrophobic surfaces.;Chapter 2 demonstrates the operation of a hierarchy of capillary interactions between concave and convex faces of different shapes in the two-dimensional self-assembly of hexagonal PDMS plates at a PDF-water interface.;Chapter 3 describes an analog model for sequence-specific recognition, using mm-sized objects (analogs of the bases of DNA, or AnBs) floating at the interface between PFD and water, and interacting through capillary forces.;Chapter 4 demonstrates templated self-assembly---based on capillary forces---of mm-scale PDMS plates suspended at the PFD-water interface. The system described abstracts the concept of "templating" from molecular templating, and uses it to design mm-scale aggregates that self-assemble in ordered structures.;Appendices I--XII include papers in print and in preparation.