Hydrodynamic-flow-driven wetting in thin film polymer blends: Growth kinetics and morphology

A thin film of deuterated poly(methyl methacrylate) (A) and poly(styrene-ra n-acrylonitrile) at the critical composition is annealed in the two phase r egion to induce simultaneous phase separation and wetting of the A-rich pha se at the surface. Using forward recoil spectrometry, the wetting layer thi ckness is found to grow linearly with time at 185 degrees C and 190 degrees C. After selective etching of A, atomic force microscopy reveals a depleti on layer having a bicontinuous, phase separated morphology. The A-rich tube s in this layer provide a pathway for rapid transport of the wetting phase from the bulk to the surface via hydrodynamic flow. Taken together, fast we tting layer growth t(1) and connectivity between the wetting layer and bulk provide unambiguous support for hydrodynamic-flow-driven wetting in thin f ilm polymer blends.