Mechanism and Strength of Polymer Bridging Flocculation

Polymer bridging flocculation is a widespread but poorly understood phenomenon, with little quantitative data available. Its strength and mechanism have been investigated by neutron diffraction experiments on a four-component clay-polymer-salt-water system. The results suggest a new mechanism: that equilibrium occurs between an entropy-driven drawing force, arising from partly stretched bridging polymers, and a bonding force to the clay platelets. The force is proportional to the number of bound segments, and the strength per polymer bridge is approximately equal to 1.4 pN. The calculation of this quantity represents a new challenge in colloid and polymer science.