Bindings of viologen oligomer to monodisperse colloidal silica particles modified with poly(maleic anhydride-styrene) for controlling of surface -potential

The -potential control of the composite particles by two-step modification of monodisperse colloidal silica, using poly(maleic anhydride-styrene) and viologen oligomer, was investigated. The binding of the viologen trimer with 4-aminopyridiyl-grafted, and poly(maleic anhydride-styrene)-modified colloidal silica (2) gave the composite particles exhibiting -positive potential of - 15 and -7 mV in pH 7.0 buffer and ethanol, respectively, while the composite 2 showed negatively high potential of -54 and -91 mV in each solution. The consecutive reaction of composite 2 using 1,4-dibromobutane and 4,4'-bipyridyl to form the oligomer led to effective elevation of -potential and gave the maximum value of +44 mV in ethanol. Exchange of the counter anion from Br- to PF6 on the composite particles, prepared by the consecutive quatemization, afforded the particles exhibiting the maximum potential of +40 mV in acetonitrile.