Chemical Grafting of Poly(ethylene oxide) onto Polystyrene Latex

Abstract

A novel method utilizing a water-soluble carbodiimide was used to chemically graft 100,000 and 615,000 g/mol PEO onto PS latex particles with mean diameters of 375 and 347 nm. Electrophoretic mobility measurements show that the PEO is truly grafted, not just adsorbed. Capillary viscometry yields a layer thickness of 23 nm for grafted 615,000 g/mol PEO. Steady shear and oscillatory rheological measurements indicate a transition from primarily liquid-like behavior to solid-like behavior at an effective volume fraction between 0.528 and 0.550. The rheological behavior is interpreted in terms of long-range repulsive particle interactions due to the grafted polymer layers. These measurements thus provide a useful probe of the relationship between polymeric interactions, suspension microstructure, and macroscopic material properties.