Fig. 4.

Alternative bulk polymer mixtures display three-phase coexistence. Coexistence of multiple surface phases requires phase separation in the bulk and is robust to the underlying details of the polymer mixture. We observe three-phase surface coexistence in all cases. (A) A unary polymer mixture with strong nearest-neighbor interactions. (B) A mixture of two short (n = 5) polymers. (C) An asymmetric polymer mixture with n = 5 (red) and n = 20 (blue). While we show three-phase coexistence for these systems, we expect all of our results would hold for these and other polymer systems prone to phase separation in the bulk.