High density scaffolding of functional polymer brushes
Orski, Sara Victoria
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The fabrication of tunable polymer coatings is of interest to materials science and biotechnology for the development of microarray chips and other small scale surface devices. Polymeric activated esters have been demonstrated as a facile route to make molecular and biomolecular polymer conjugates. This dissertation details the design, synthesis, and applications of poly(n-hydroxysuccinimide 4-vinyl benzoate) (poly (NHS4VB)) brushes as a versatile method for creating scaffolds for post-polymerization modification with spatial and temporal control of surface functionality. The active ester brushes were designed to have uniform morphology, controlled polymerization rate, and block copolymer–tuned microenvironments using living polymerization methods. Poly(NHS4VB) brushes were derivatized with various reactive alkynes that differ in relative rates of activity in azide-alkyne cycloaddition reactions. Relative rates of polymer brush functionalization to their solution counterparts are compared to help to determine the extent of polymer brush functionalization and elucidate the influence of polymer brush architecture for post-polymerization functionalization reactions. Poly(NHS4VB) brushes can also template multicomponent surfaces with spatially resolved functionality by both “top down” and “bottom up” methods. Poly(NHS4VB) brushes modified with a cyclopropenone-protected dibenzocyclooctyne were patterned using photolithography to selectively activate a strained alkyne moiety for catalyst-free cycloaddition with azides. Bottom up templating of multifunctional surfaces was demonstrated by orthogonal self-assembly of catechol functionalized initiators and subsequent active ester polymerization on titanium oxide selectively in the presence of silicon oxide. Further incorporation of chemical and spatial complexity was introduced by synthesis of a second functional polymer brush, poly(ethynyl styrene), from the remaining silicon oxide sites. High fidelity patterns of surface functionality were demonstrated in both top down and bottom up patterning methods by fluorescence microscopy of two fluorescent dyes selectively bound to the brush surfaces. Selective immobilization of dual-functional polymer brushes can be pragmatic to the design of customizable polymer brush coated nanostructures for tunable nanotechnology applications. This dissertation is the culmination of the design, fabrication, and characterization of easily patterned and customizable polymer brush scaffolds for small scale devices and nanomaterial uses.