INTERPLAY BETWEEN PHASE-SEPARATION AND WETTING FOR A POLYMER MIXTURE CONFINED IN A 2-DIMENSIONAL CAPILLARY - WETTING-INDUCED DOMAIN ORDERING AND COARSENING

For a binary polymer mixture sandwiched between two glass plates it is found that near the symmetric composition, wetting-induced domain ordering leads to an unusual morphological transformation from an initial bicontinuous pattern in bulk to an assembly of disklike droplets connected via the wetting layers, and back to a two-dimensional (2D) bicontinuous pattern. The droplet pattern temporarily appears during the process of the dimensional crossover from 3D to 2D since the in-plane symmetry of the order parameter is broken by the wetting layers even for a symmetric mixture. Coarsening of the droplet pattern is dominated by its interconnected nature: a droplet is likely to interact with the neighbouring droplets by the tube hydrodynamic instability unique to bicontinuous fluid structure.