This paper describes a method for growing thin polymer films from the surface of a silicon wafer bearing a native oxide (Si/SiO 2 ) by ring-opening metathesis polymerization (ROMP). 1,2 We have prepared norbornenederived polymer films with a wide range of thicknesses (up to 1 µm) and with a control over the chemical composition of the film perpendicular to the surface. Recently, surface-initiated polymerization has become an area of great interest, and several groups have developed approaches to grow thin polymer films on silicon and gold using cationic, anionic, and radical methods. 3 However, these methods often require rigorous reaction conditions and/or an input of thermal energy and have limited abilities to produce films of controlled thickness and chemical composition. Notably, Weck et al. recently reported the use of ROMP in a surface-initiated polymerization. 1b In their work, the polymerization was allowed to occur only at defects within a self-assembled monolayer (SAM) and yielded an extremely small amount of a polymeric material on the surface. Characterizations of the polymerization process and the resulting polymer were not possible. In this paper, we present the use of surface-initiated ROMP as a strategy for offering a high degree of control over a surface polymerization process that occurs at room temperature and demonstrate its use in the facile formation of patterned polymer films on silicon when used with the technique of microcontact printing (µCP).Scheme 1 outlines our three-step procedure: (i) the formation of a self-assembled monolayer (SAM) on silicon that presents norbornenyl groups; (ii) the attachment of a ruthenium catalyst [(Cy 3 P) 2 Cl 2 RudCHPh, Cy ) cyclohexyl] (1) to the surface using the norbornenyl groups; (iii) the polymerization of added monomers to generate the film. 4 In the first step, a SAM of 5-(bicycloheptenyl)trichlorosilane (2) was formed on a Si/SiO 2 surface by immersing a UV-ozone cleaned substrate in a toluene solution of 2 (60 mM) for 6-12 h. The presence of the resulting 0.6 nm thick film of 2 was confirmed by attenuated total reflection (ATR) IR spectroscopy (see the Supporting Information) and ellipsometry. We then attached an immobilized derivative of catalyst 1 to this norbornenyl surface by dipping the substrate into a CH 2 -Cl 2 solution of 1 (17 mM) for 30 min. Subsequent exposure of the substrate to norbornene-based monomers such as 5-(bicycloheptenyl)triethoxysilane (3) or exo-N-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide (4) (0.01-0.4 M) in CH 2 Cl 2 produced a polymeric film on the surface. Typical polymerization times were 30 min, and the substrate was washed extensively with CH 2 Cl 2 between each step. We characterized the resulting films by transmission IR spectroscopy, ellipsometry, optical microscopy, scanning electron microscopy, and atomic force microscopy (AFM).Parts a and b of Figure 1 show transmission IR spectra of films of poly-3 and poly-4 on silicon, respectively, prepared by the procedure in Scheme 1. In Figure 1a, the str...

Patterned polymer films were grown on SiO 2 /Si surfaces by a process starting with microcontact printing ͑CP͒ of octadecyltrichlorosilane ͑OTS͒, formation of a monolayer derived from norbornenyl trichlorosilane (Nbn-SiCl 3) in areas not protected by OTS, activation of the surfaces derived from Nbn-SiCl 3 with a ruthenium catalyst, and surface-initiated ring-opening metathesis polymerization of derivatives of norbornene by the catalytically active ruthenium species. These patterned polymer films were successfully used as reactive ion etching resists. The combination of CP and surface-initiated polymerization makes possible molecular-level control of polymer composition and thickness in both lateral and vertical directions: the smallest patterned lateral features were 2 m lines; this width was determined by the features of the stamp used in CP and is not the intrinsic limit of the method. The thickness of the polymer film was, typically, 5-100 nm and could be controlled by monomer concentration and reaction time.

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