Appl. Phys. A 74 [Suppl.], S433–S435 (2002) / Digital Object Identifier (DOI) 10.1007/s003390201884 Applied Physics A Materials Science & Processing Structure analysis of adsorbed star-like polymers with GISAS and SFM M. Wolkenhauer 1, ∗ , P. Müller-Buschbaum 2 , O. Wunnicke 3 , M. Stamm 3 , J. Roovers 4 , G. von Krosigk 5 , R. Cubitt 6 1 MPI für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany 2 TU München Physik Department, LS E13, James-Franck-Strasse 1, 85747 Garching, Germany 3 IPF Dresden e.V., Hohe Strasse 6, 01069 Dresden, Germany 4 ICPET, National Research Council of Canada, Ottawa, K1A 06, Canada 5 Hasylab/DESY, Notkestrasse 85, 22603 Hamburg, Germany 6 ILL, B.P. 156, 38043 Grenoble Cedex, France Received: 16 July 2001/Accepted: 13 November 2001 –  Springer-Verlag 2002 Abstract. The lateral structures of dried adsorbed binary mix- tures of star polymers were investigated. Blends of proto- nated and deuterated polybutadiene stars were prepared from cyclohexane solutions and adsorbed onto silicon substrates. The number of arms and the molecular weight of the arms was varied. With grazing incidence small angle scattering techniques (GISAS) and scanning force microscopy (SFM), different dominant in-plane length scales were determined. The morphology of these structures is dominated by blob-like structures created from single stars or agglomerates of star polymers. PACS: 68.55.Jk; 68.45.Da; 28.20.Cz The adsorption of polymers at the solid/solution interface is of interest in many industrial processes. Regular star poly- mers are branched polymers which show a spread behavior depending on their functionality and the molecular weight of the arms. The architecture of regular star polymers can be di- vided into a core part consisting of a dendrimer and a shell part consisting of attached linear chains. This core-shell top- ology leads to a non uniform monomer density distribution yielding a non uniform osmotic pressure increasing from the shell to the core. The adsorption behavior and the conforma- tion of adsorbed star polymers depends on the interactions between solvent and polymer, the free energy of deformation, the free energy of the adsorption of the monomeres and the repulsive arm-arm interaction [1, 2]. The last contribution, in particular present for star polymers, results from the osmotic pressure. To investigate the latter contribution solutions of two star polymers with different numbers of arms were prepared. 1 Sample preparation and experimental setup Samples: Polybutadiene (PB) star polymers were synthesized by anionic polymerization. Living polydiene was prepared by ∗ Corresponding author. (Fax: +49-6131/379-100, E-mail: wolken@mpip-mainz.mpg.de) using s-BuLi as initiator. The polydiene was linked on den- drimeric chlorosilane with the appropriate multifunctionality. A detailed description of the synthesis can be found else- where [3]. All polymers used are listed in Table 1 with their key parameters: functionality f , molecular weight M w and radius of gyration R g (measured by SANS in cyclohexane 1 ). For the adsorption, silicon Si(100) wafers, with a native oxide layer, were used as substrates. To obtain identical sur- faces all silicon wafers were cleaned by the following pro- cedure: First the substrates were placed in dichlormethane in an ultrasonic bath for 15 min at 40 celsius to remove the organic surface contamination. Next the silicon wafers were rinsed with Milli-Pore water and treated with an acid oxi- dation bath of H 2 O 2 ,H 2 SO 4 and Milli-Pore water at 80 ◦ C for 15 min. Afterwards the wafers were rinsed with Milli- Pore water. Compressed (dust-free) nitrogen was used to dry the wafers. Finally the wafers were stored for 2 days to en- sure that the growth of the newly build-up native oxide layer reached an equilibrium. A total solution concentration of 0.001 mg/ml PB in cy- clohexane was chosen. Out of these solutions binary mix- tures with equal concentration of both kinds of star solutions were prepared. The substrates were stored for 24 h in these binary mixtures and after removal, rinsed with cyclohexane 1 Performed at the SANS2 beamline at the GKSS Research Center. Avail- able q-range: 0.01 nm -1 < q < 2.4 nm -1 Table 1. Star polymers, molecular weight M w , radius of gyration ( a SANS in cyclohexane) and number of arms f (h 1 protonated, d 2 deuterated) sample f M w (10 5 g/mol) R a g (nm) PB1815h 1 18 2.6 8.6 PB1825h 1 18 4.4 17.4 PB3210h 1 32 3.01 9.1 PB3216h 1 32 5.58 13.4 PB3237h 1 32 13.3 22.2 PB6430h 1 64 13.4 18.5 PB6407d 2 64 3.95 8.0 PB12807d 2 128 8.4 8.6