Dewetting of thin polymer-blend films examined with GISAS

The morphology of dewetted thin polymer-blend films of deuterated polystyre ne (dPS) and polyparamethylstyrene (PpMS) on top of silicon surfaces is inv estigated. The film thickness of the originally homogeneous films is varied between 19 and 104 Angstrom. Compared to the radius of gyration of the unp erturbed molecule, R-g = 106 Angstrom, the as-prepared films are confined i n the direction perpendicular to the sample surface. The dewetting results from the storage of the samples under toluene vapor atmosphere. Atomic forc e microscopy (AFM) and grazing incidence small-angle scattering (GISAS) are used. From the differences in the GISAS data measured with X-rays compared to data measured with neutrons a random distribution of the molecules insi de the individual droplets is determined. Thus from dewetting under toluene atmosphere no periodicity in the internal structure exists. The, within al l methods derived, most prominent in-plane length corresponds to the mean d roplet distance. Its function of film thickness is explainable by the spino dal dewetting model. (C) 2000 Elsevier Science B.V. All rights reserved.