Fluctuation-induced forces in critical crosslinked polymer blends

Abstract

In this paper, we report on the computation of the induced forces in crosslinked polymer blends, with immersed small colloidal particles (nanoparticles) or confi ned to two parallel plates (fi lm). We assume that the particles or the walls prefer to be attracted by one polymer, close to the spinodal temperature where a microphase separation takes place. This is the so-called " critical adsorption " . As an assumption, the particle diameter or the fi lm thickness is considered to be small enough in comparison with the size of microdomains ( " mesh size " ). The critical fl uctuations of the crosslinked mixture induce a pair potential between particles located in the nonpreferred phase or between the confi ning walls. The purpose is to recall how this Casimir pair potential can be determined, as a function of the interparticle distance or the walls separation. To achieve calculations, use is made of an extended de Gennes model that takes into account the colloid-polymer and polymer-wall interactions. Finally, the obtained results are compared to those relatively to uncrosslinked polymer blends in the same geometries, and the main conclusion is that the induced force is reduced by the presence of permanent crosslinks.