Understanding morphology evolution and roughening in phase-separating thin-film polymer blends

Using forward recoil spectrometry and atomic force microscopy, the entire p hase evolution is revealed for a critical thin-film blend deposited on a su bstrate undergoing symmetric netting and phase separation. The three main s tages are characterized by a trilayer structure, interphase coarsening, and surface roughening. Capillary fluctuations are shown to cause spontaneous rupturing of the interphase resulting in an interconnected network, which e ventually forms encapsulated droplets. The surface roughness grows rapidly at first, remains relatively constant (ca. 12 nm), and then increases rapid ly to a final macroscopic value of 245 nm, about half the original film thi ckness.