| dc.description.abstract | The work presented herein focuses on the growth of poly(hydroxyethyl methacrylate) (PHEMA) films on gold by water-accelerated, surface-initiated atom transfer radical polymerization and derivatization of these films with fluorocarbon and hydrocarbon groups using simple post-polymerization reactions. Hydroxyl groups of PHEMA may be reacted with perfluoroalkyl, perfluoroaryl, and alkyl acid chlorides to incorporate these groups onto the polymer side chains. Fundamental studies of the effects of modification chain length and composition on film structuring and surface and barrier properties are presented. Film surface energy can be tuned by choice of modifying species, with long perfluoroalkyl side chains resulting in extremely hydrophobic, oleophobic surfaces. Structured films result from modifications with long alkyl and perfluoroalkyl chains, while barrier properties are mostly dependent on conversion of hydrophilic hydroxyl groups but also on film and interfacial structuring.
Block-like copolymer films are created by the controlled, diffusion-limited hydrolysis of perfluoroaryl-modified PHEMA films followed by reactive modification. Hydrolysis, which regenerates hydroxyl groups, is confined to a region near the film surface. Rederivatization of these hydroxyls with a second modifying species, particularly perfluoroalkyl groups, allows surface hydrophobicity/oleophobicity and barrier properties of the copolymer films to be simultaneously optimized. The fundamental knowledge of modification effects from the initial portions of this work are utilized in the creation of block-like copolymer films to gain even more engineering control over bulk and interfacial film properties.
Film derivatization techniques can also be applied to the microscale using microcontact printing to pattern polymer film growth. Directly patterning the growth of films onto the surface retains bare gold regions, which can be used for further processing, on the remainder of the substrate. We have grown polymethylene in the interspersed gold regions of patterned PHEMA and fluorinated PHEMA to create films having either hydrophilic/hydrophobic or fluorocarbon/hydrocarbon microdomains, which are difficult to create using other methods. The array of film engineering techniques demonstrated may be useful in a variety of applications, including non-wetting and barrier coatings, membranes, dielectrics, etch resists, and microfluidic devices. | |
