Synthesis of nanometer-scale polymeric structures on surfaces from template assisted admicellar polymerization: a comparative study with protein adsorption.

A novel method for the formation of nanometer-scale polymer structures via template assisted admicellar polymerization (TAAP) is described. Admicellar polymerization uses a surfactant layer adsorbed on a surface to localize monomer to the surface prior to polymerization of the monomer. Nanostructures are formed by restricting adsorption to the uncovered sites of an already-templated surface, in this case to the interstitial sites between adsorbed latex spheres. Unlike most other process that form polymer nanostructures, polymer dimensions can be significantly smaller than the interstitial size because of sphere-surfactant interactions. Protein adsorption in the interstitial sites of colloidal arrays was also studied for three different proteins, and the results were compared with those obtained via admicellar polymerization.

Adsorbed surfactants as templates for the synthesis of morphologically controlled polyaniline and polypyrrole nanostructures on flat surfaces: from spheres to wires to flat films.

Nanostructures of polyaniline (PAni) and polypyrrole (PPy) with controlled morphologies have been synthesized on atomically flat surfaces using adsorbed surfactant molecules as templates. Atomic force microscopy (AFM) has been used to investigate polymer film formation on highly oriented pyrolytic graphite (HOPG) and chemically modified HOPG. Morphological control over the resulting polymer film is possible by the addition of coadsorbing molecules, manipulation of the length of the surfactant hydrophobe, or by changing the surface chemistry of the adsorbing substrate. Phase transitions between spheres, cylinders/wires, and featureless films have been observed which exactly parallel transitions between spheres, cylinders, and flat layers in the adsorbed surfactant. Parallel arrays of PAni nanowires can be synthesized with alignment evident over large areas in a simple self-assembly technique in which fabrication and arrangement take place simultaneously. Such a technique in which one can engineer sub-100-nm-ordered nanoscale pi-conjugated polymer structures of a desired shape by a simple self-assembly process presents potential as templates, sensors, and microelectronic devices.

X-ray photoelectron spectroscopic studies of hydrophilic surfaces modified via admicellar polymerization.

Admicellar polymerization with styrene monomer was used to coat the surface of two porous solids: titanium dioxide and alumina. X-ray photoelectron spectroscopy (XPS) measurements clearly indicate that after admicellar polymerization, organic material and surfactant are present on the surface of the solids. Water washes, performed immediately after admicellar polymerization, were successful in removing approximately 30% of the organic material, presumably mostly surfactant. The water wash was followed by Soxhlet extraction with toluene, with no measurable removal of organic material according to ignition loss measurements of the solid, gel permeation chromatography of the extracting solvent and also UV/VIS spectroscopy of the extracting solvent. However, there was a 5-15% drop in organic material after Soxhlet extraction according to XPS measurements. This difference is attributed to the difference in sampling; XPS samples only the exterior surface area while these bulk measurements sample both the interior and exterior surface area. This study details the ability of different washing steps to remove materials from the porous substrates used in this study.