Dispersions of hydrophilic silica particles, which are charge-stabilised in ethanol, may be flocculated on the addition of sufficient cyclohexane. The primary mechanism is the reduction in the zeta potential. The flocculation observed is kinetically controlled; it is irreversible and time dependent. By way of contrast, dispersions of hydrophobised particles (i.e., silica particles carrying terminally-grafted n-octadecyl chains) in cyclohexane are uncharged and behave virtually as dispersions of hard-sphere particles. Addition of ethanol, beyond a critical concentration leads to particle "phase separation" (weak flocculation); this is thermodynamically controlled.
ASJC Scopus subject areas