Mixed monolayer and multilayer films of functionally terminated oligomers: Design of superstructures

Date of Completion

January 1996

Keywords

Chemistry, Polymer|Engineering, Chemical|Physics, Molecular

Degree

Ph.D.

Abstract

Molecular assemblies represent a fundamental limit in miniaturization. Controlling assemblies at the molecular level has application in sensors, photonics, and fundamental studies of surface behavior. While the preparation and handling of inorganic layers atoms thick is well developed in the microelectronics industry, the same techniques cannot be applied to organic materials. Langmuir-Blodgett is a facile technique to assemble, align, and deposit molecular layers of organic materials in monolayers and multilayers of macroscopic dimensions. In this manner control over each individual layer is possible and three dimensional superstructures can be built with mixed multilayers. The LB technique was used to construct monolayers and multilayers of functionally terminated oligomers of 1,2-hydrogenated poly(butadiene) and poly(dimethylsiloxane). The difunctional materials form extended chains that affect the layer wetting, but not enough to control the deposition process unless a multifunctional polyelectrolyte is used as the counter-ion. ADXPS and XSW were used to determine the presence of extended chains in the layers by locating the chain ends. Both techniques provide significant but incomplete information on the position of the end groups. Taken together they show a transition from extended to looped chains between 1000 and 3400 molecular weight, with some dependence on the polydispersity.^ In phase separated mixed monolayers the functional groups are used to control domain morphology. Domain size can be varied from millimeters to nanometers by controlling acid-ion or acid-base interactions. Superstructures of mixed multilayers are amenable to scanning probe microscopy techniques, which can distinguish the individual mixed layers in a mixed multilayer. ^

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