Film-Forming Microgels for pH-Triggered Capture and Release

PAUL A. FITZGERALD; JAVIER I. AMALVY; STEVEN P. ARMES; ERICA J. WANLESS

LANGMUIR

American Chemical Society

Año: 2008 vol. 24 p. 10228 - 10234

0743-7463

The pH-responsive behavior for a series of lightly cross-linked, sterically stabilized poly(tertiary amine methacrylate)-based latexes adsorbed onto mica and silica was investigated using in situ tapping mode AFM at room temperature.The adsorbed layer structure was primarily determined by the glass transition temperature, Tg, of the latex: poly-[2-(diethylamino)ethyl methacrylate]-based particles coalesced to form relatively featureless uniform thin films, whereasthe higher Tg poly[2-(diisopropylamino)ethyl methacrylate] latexes retained their original particulate character. Adsorptionwas enhanced by using a cationic poly[2-(dimethylamino)ethyl methacrylate] steric stabilizer, rather than a nonionicpoly(ethylene glycol)-based stabilizer, since the former led to stronger electrostatic binding to the oppositely chargedsubstrate. Both types of adsorbed latexes acquired cationic microgel character and swelled appreciably at low pH,even those that had coalesced to form films. Fluorescence spectroscopy was used to study the capture of a modelhydrophobic probe, pyrene, by these adsorbed latex layers followed by its subsequent release by lowering the solutionpH. The repeated capture and release of pyrene through severalpHcycles was also demonstrated. Since these poly(tertiaryamine methacrylate) latexes are readily prepared by aqueous emulsion polymerization and adsorption occurs spontaneouslyfrom aqueous solution, this may constitute an attractive route for the surface modification of silica, mica and otheroxides.