Adsorption Behavior at the Air/Water Interface for PNIPAM-adsorbed Colloidal Silica

Adsorption behavior at the air/water interface was examined for colloidal silica, on which poly(N-isopropylacrylamide) (PNIPAM) was physically adsorbed, by a dynamic surface tension measurement with the Wilhelmy plate method. The suspension of PNIPAM-adsorbed silica exhibited a decrease in surface tension after a very long induction time, while a bare silica suspension showed no surface activity. The decay rate of surface tension increases with increasing amount of PNIPAM adsorbed on the silica, even for suspensions with the same polymer concentration.