Polysilazane-induced aggregation of hydrophobic silver colloids

Adsorbing polymers such as polysilazanes induce irreversible coagulation of hydrophobic silver colloids in nonpolar solvents. This is accompanied by broadening of the surface plasmon resonance (SPR) peak. A method to analyze the coagulation kinetics based on von Smoluchowski's theory utilizing the SPR change is described. The approach allows evaluating extinction spectra of aggregates of small sizes. A model for polymer adsorption kinetics in combination with a modified bridging efficiency model explains the observed coagulation inhibition over time in terms of macromolecules adsorption, spreading, and mutual repulsion.