1) Surface Tuning: Mixed Functionality Control on Surfaces:
In the surface modification, we utilize the surface tuning technique using multiple functional materials to control surface energetics, functionality, porosity, and topography, and to develop engineered substrates for applications in coating, adhesives, laminates, painting, printings, and display materials. For example, 30 % amine-terminated silane-coated aluminum substrates proved to be an optimum substrate for carboxylated polybutadiene adhesion. For the study, in my PhD work, I prepared the intermediate surface energetics by controlling the density of receptor groups using a mixed self-assembly. The incompatibility of hydrophobicity or hydrophilicity between a polymer and a solid surface can be overcome through many industrial techniques such as laser, plasma, and ozone treatments. These treatments improve the strength of the polymer-solid interface. However, the uncertainty of the molecular scale structures prepared by techniques makes it difficult to understand the receptor density effect on polymer adhesion on a molecular level. The surface-tuned substrate can be very useful in coating, painting, and printing industry.
Surface tuning, the control of composition and surface chemistry over surface and interface, can also be obtained using layer-by-layer techniques with weak polyelectrolytes (Rubner, M. F group. MIT). The layer-by-layer processing of polyelectrolytes into multilayer thin films is very suited for this surface and interface control. Weak polyelectrolytes are ionic polymers with linear charge densities that are tunable by simple pH adjustments: typically in the pH range of 2-10. When both the polycation and polyanion are weak polyelectrolytes, the pH of a dipping solution can be used to control the charge density of an adsorbing polymer. Specific examples of what can be accomplished with weak polyelectrolyte multilayer assembly are light emitting thin film devices and micro-porous thin films. Using this layer-by-layer approach, it is possible to coat large areas with films of uniform thickness, low surface roughness and very low pin-hole densities, or even micro-porous thin films by pH driven morphological reorganizations.
. I. Lee and R. P. Wool, ¡°Controlling Amine Receptor Group Density on Aluminum Oxide Surfaces by Mixed Silane Self Assembly,¡± Thin Solid Films, 379, pp94-100 (2000).
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