Atomic force microscopy studies of admicellar polymerization polystyrene-modified amorphous silica

• Published in: Journal of applied polymer science 2003-01, Vol.87 (2), p.290-299
• Main Authors: See, Chun Hwa, O'Haver, John
• Format: Article
• Language: English
• Subjects: Applied sciences; atomic force microscopy (AFM); Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; silicas; surfactants; thin films
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.11424

Atomic force microscopy was used to study polystyrene‐modified silica surfaces produced by admicellar polymerization (polymerization of monomers solubilized in adsorbed surfactant aggregates). The goal was to examine changes in the location and nature of the formed polystyrene resulting from changes in the surfactant and monomer feed levels on precipitated silica. Normal tapping and phase‐contrast modes in air were used to image the topography of the polystyrene‐modified silica. Moderate‐to‐light force‐tapping mode was used to differentiate between the silica surface and adsorbed water or polymer. The formed polystyrene exists primarily in the pores, with patches extending onto the exposed surface of the silica particles. At moderate tapping forces, darker phase regions were observed in the valleys and pores of the silica in both the modified and the unmodified samples. Upon higher magnification, the darker regions disappear on unmodified silicas, whereas polymer bands become evident on the modified silicas. At lower loadings of surfactant and monomer, the number and extent of polymer patches decreased, with polymer being found only in pores. The polystyrene patches observed inside the valleys of the amorphous silica varied from 1 to 10 nm in thickness. The structure of the polystyrene film formed on precipitated silica was found to be insensitive to the surfactant feed concentration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 290–299, 2003