Effective interaction between nanoparticles mediated by a symmetric polymer blend.

We analytically study the polymer-mediated (PM) interactions between spherical particles immersed in a symmetric polymer blend. By making use of standard methods of the liquid state theory we have found out a nonconventional mechanism of the PM interactions caused by nonuniformities in the local composition of the polymer blend induced by the particles. The relative significance of the contributions to the PM interaction potential due to the finite compressibility of the polymer blend and its compositional nonuniformity is found to drastically depend on the polymer-to-particle size ratio. In the protein limit of relatively small particles, the mechanism due to the compositional nonuniformity, specific to polymer blends, is shown to play a dominant role in the PM interactions.