* Corresponding author. Fax: #48-12-633-7086. E-mail address: ufbudkow@cyf-kr.edu.pl (A. Budkowski). Vacuum 63 (2001) 297}305 Phase decomposition in polymer blend "lms cast on homogeneous substrates modi"ed by self-assembled monolayers B. Bergues, J. Lekki, A. Budkowski*, P. Cyganik, M. Lekka, A. Bernasik, J. Rysz, Z. Postawa Smoluchowski Institute of Physics, Jagellonian University, ul. Reymonta 4, 30-059 Krako & w, Poland Institute of Nuclear Physics, Radzikowskiego 152, Krako & w, Poland Surface Spectroscopy Laboratory, University of Mining and Metallurgy, Krako H w, Poland Joint Centre for Chemical Analysis and Structural Research, Jagellonian University, Krako & w, Poland Abstract Thin "lms, formed by polymer blends spun-cast from a blend/solvent solution onto a rigid substrate, are used in many practical applications (e.g. photoresist layers, dielectric coatings). Film preparation process is often accompanied by phase decomposition (PD) during the rapid evaporation of the solvent. PD is re#ected in undulations formed on an air/"lm interface. We have studied the topography of surface undulations and the phase domain morphology in thin "lm blends of polystyrene (PS) and polyisoprene (PI) using atomic force microscopy combined with selective dissolution of blend components. Gold covered with self-assembled monolayers [HS(CH  )  COOH]  [HS(CH  )  CH  ]  (SAM  ) was used as a substrate. For "lms of PS and PI (50% by mass) cast from toluene, the PS-rich domains protrude high above the PI-rich matrix forming concave or convex islands for hydrophobic (SAM  )- or hydrophilic (SAM  )-support, respectively. Di!erent substrates (e.g. SAM  and Si with a native oxide layer), solvents (CCl  , chloroform) and PS mass fractions were used to evaluate the extent of this novel e!ect.  2001 Elsevier Science Ltd. All rights reserved. Keywords: Phase separation morphology; Thin "lms; Polymer blends; Self-assembled monolayers; Atomic force microscopy 1. Introduction Phase decomposition (PD) of polymer blends is driven by the quench into the metastable or unsta- ble regions of the phase diagram. Polymer mobility is promoted by temperatures above the glass transition ¹  (temperature quench) or by a com- mon solvent added to the mixture (solvent quench). Bulk PD, resulting in an isotropic morphology of phase domains, is reasonably well understood. The e!ects of boundary surfaces on PD in thin "lms of the blend have been studied only in the past decade [1]: the surface breaks the symmetry of the polymer mixture and preferentially attracts one of the blend components leading to an anisotropic, surface- oriented mode of PD [1}4] or the formation of a wetting layer [5}7]. Di!erent "nal equilibrium morphologies of self-organised domain structures are formed depending on the chemical nature of the substrate [7,8]. A controlled variation of the 0042-207X/01/$- see front matter  2001 Elsevier Science Ltd. All rights reserved. PII:S0042-207X(01)00205-6