Interfacial design with polydiacetylene monolayers.

Recent advances in self-assembly chemistry have expanded the utility of polymeric systems for applications such as studying small molecule partitioning and sensor design, which often require a high degree of control over the structure of organic interfaces. In particular, the use of photopolymerizable diacetylene monomers with self-assembling moieties enables the fabrication of robust polymers within a single molecular layer, with nanometer-scale control of the polymer physical structure. The formation of these unique polymer films is accomplished by the spontaneous assembly of alkyl precursors containing conjugated diacetylene groups on gold surfaces. The resultant well-defined monomer assembly is covalently linked through UV photopolymerization, forming a highly conjugated polymer backbone which provides unique optical and electronic properties. The structure of these polymers is controlled synthetically by varying the monomer precursors. These subtle variations in structure have a profound impact on the global physical, electronic, and viscoelastic properties of the polymer interfaces. In order to effectively utilize these polydiacetylene thin films for novel interfacial design applications, the structure-property relationships are investigated in detail. Infrared spectroscopy is applied to evaluate both the crystallinity and orientation of the polymethylene chains. In addition, the polymerization efficiency, kinetics, and colorimetric phase behavior of the polydiacetylene backbone are investigated using Raman spectroscopy. These spectroscopic results indicate that the polymer phase can be controlled with relatively minor variations in monomer structure. Furthermore, atomic force microscopy, as well as electrochemical and traditional wet chemistry techniques combine to provide a complete understanding of how variations in polymer structure can be used to design polymer interfaces with targeted properties for applications in sensor design, as model membranes, and in chromatographic separations. In addition, the utility of these single layer polymers as photo-resists in lithographic applications for controlling the physical structure and chemical properties of interfaces is demonstrated using scanning electron microscopy and resonance Raman imaging techniques. These results show that PDA monolayers can be used to accurately and reproducibly pattern gold surfaces. Ultimately, the utility of photopolymerizable diacetylene monolayers for controlling interfacial structure and properties in three dimensions is demonstrated.PhDAnalytical chemistryPhysical chemistryPolymer chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131961/2/9938499.pd