Measurement of long-range steric repulsions between microspheres due to anadsorbed polymer - art. no. 011401

We have measured the interparticle potential between pairs of micron-sized silica spheres induced by adsorbed polyethylene oxide polymer using a line- scanned optical tweezer. We found this long-range steric repulsion to be ex ponential over the range of energies (0.1k(B)T-5k(B)T) and polymer molecula r weights (452 000-1 580000) studied, and that the potential scaled with th e polymer's radius of gyration R-G. The potential's exponential decay lengt h was about 0.6R(G) and its range was about 4R(G). although both parameters varied significantly from one pair of spheres to another. The potential's exponential prefactor was greater than mean-field predictions.