Critical properties of thin films of polymer solutions

Abstract

The critical properties of polymer solutions confined in thin-film environments is studied with simple scaling arguments and a molecular theory. For purely repulsive surfaces, the critical volume fraction is a universal function of x = N1/2/L, where N is the chain length and L is the film thickness. The critical volume fraction is nonmonotonic in x and shows a deep minimum at a film thickness several times larger than the chain's radius of gyration. This nonmonotonic behavior results from the interplay between the surface–polymer entropic repulsion and the tendency of the film to avoid large density gradients. The critical temperature is a monotonically increasing function of L, as L goes from the two-dimensional limit to the three-dimensional limit. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1849–1853, 2005