Alternate sign reversal in the zeta potential and synchronous expansion and contraction in the absorbed multi-layers of poly(4-vinyl-N-n-butylpyridiniutn bromide) cations and poly(styrene sulfonate) anions on colloidal silica spheres

Alternative multiple absorbed layers of up to ten macrocations [poly(4-viny l-N-n-butylpyridinium bromide)] and macroanions [sodium poly(styrene sulfon ate)] are formed on colloidal silica spheres above the critical concentrati on of macroions, m*. The m* value is the minimum number of macroions requir ed to reverse the sign of the zeta potential of the spheres in the first ab sorption step. Alternative sign reversal in the zeta potential and expansiv e-contractive thickness changes are observed by the repeated and alternate addition of macrocations first and macroanions next. During multiple absorp tion, the pH and conductivity values decrease and increase continuously as the number of absorbed layers increases. When the macroanions are added fir st, sign reversal in the zeta potential and reversible expansion and contra ction do not occur. Breaking of the alternate multiple-type absorption occu rs when equivalency in the number of dissociative groups of macrocations an d macroanions is broken. Synchronous conformational changes of macrocations and macroanions in the multiple-absorbed layers, where balancing of the co nformational rigidities with the multiple electrostatic attraction and repu lsion between macrocations and anions occurs, are supported strongly.