DEWETTING DYNAMICS AND NUCLEATION OF POLYMERS OBSERVED BY ELASTIC ANDFRICTION FORCE MICROSCOPY

Dewetting dynamics of immiscible liquid polymer bilayers were studied by atomic force microscopy. Morphological changes of the phase-separat ed liquids were correlated with friction and local elastic properties, and the dewetting pattern classified in terms of the relative bulk vi scosities. Topographical atomic force microscopy measurements revealed that the dewetting process did not occur on the liquid-liquid interfa ce as expected. Rather the process is three-dimensional with an appare nt shear plane ''deep'' inside the tow viscosity liquid film, The dept h of the shear plane is immediately established in the nucleation proc ess which was studied two and three dimensionally by friction force mi croscopy and compliance measurements. Since this mechanism has not bee n observed previously in simple liquids, the role of entanglements of these polymers is discussed together with the application of the atomi c force microscopy as a three-dimensional material property specific t ool capable of studying processes below the surface. (C) 1996 American Vacuum Society.