Molecular Aggregation State of <i>n</i>-Octadecyltrichlorosilane Monolayer Prepared at an Air/Water Interface

Kojio, Ken; Ge, Shouren; Takahara, Atsushi; Kajiyama, Tisato

doi:10.1021/la970040p

Cited by 91 publications

(88 citation statements)

References 18 publications

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“…Moreover, complete cross-polymerization would yield an area per chain of around 11 2 , which is not possible and not observed. Instead, the experimentally observed area per chain of 21-25 2[26, 41-45] is more consistent with the area per chain of 20-24 2 that was found for hexagonally close-packed Langmuir-Blodgett layers of OTS, [46,47] thus indicating that SAMs on SiO 2 are very similar to Langmuir-Blodgett layers.…”

Section: Mechanism Of Formationsupporting

confidence: 66%

Engineering Silicon Oxide Surfaces Using Self‐Assembled Monolayers

2005

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Although a molecular monolayer is only a few nanometers thick it can completely change the properties of a surface. Molecular monolayers can be readily prepared using the Langmuir-Blodgett methodology or by chemisorption on metal and oxide surfaces. This Review focuses on the use of chemisorbed self-assembled monolayers (SAMs) as a platform for the functionalization of silicon oxide surfaces. The controlled organization of molecules and molecular assemblies on silicon oxide will have a prominent place in "bottom-up" nanofabrication, which could revolutionize fields such as nanoelectronics and biotechnology in the near future. In recent years, self-assembled monolayers on silicon oxide have reached a high level of sophistication and have been combined with various lithographic patterning methods to develop new nanofabrication protocols and biological arrays. Nanoscale control over surface properties is of paramount importance to advance from 2D patterning to 3D fabrication.

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Section: Mechanism Of Formationsupporting

confidence: 66%

Engineering Silicon Oxide Surfaces Using Self‐Assembled Monolayers

2005

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“…19,31,34 The van der Waals forces between the chains act to orient the chains so that they are normal to the surface of the substrate. The characteristic area per chain approaches 0.21-25 nm 2 /chain [35][36][37] for these films. 2Cl films also can form both surface-chain and interchain siloxane linkages, but the methyl group on each alkylsilane molecule sterically restricts interchain bonds.…”

Section: Comparison Of Thicknesses Of 1cl 2cl and Ots Films For Quamentioning

confidence: 83%

“…Consequently, we expect that for SAMs of OTS either the solvent is not excluded significantly from the compressed region under the tip or that solvent may ''channel'' through the SAM via a network of defects. ''Channeling'' that results in a larger diffusion coefficient is plausible because the molecular areas achieved in SAMS of OTS 0.21-25 nm 2 /chain 35,36,53 are larger than the molecular area of the 0.19 nm 2 /chain of the LB films of arachidic acid used by Vanderlick and coworkers. Also, SAMs of OTS do not display a long-range, quasicrystalline structure.…”

Section: Influence Of Load On Friction Maxima Changes With Chain Densitymentioning

confidence: 99%

The effect of chain density on the frictional behavior of surfaces modified with alkylsiloxanes and immersed in n-alcohols

Clear

Nealey

2001

The Journal of Chemical Physics

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Concepts of viscoelastic behavior of bulk polymer systems were used to describe maxima in the friction behavior of self-assembled monolayers ͑SAMs͒ measured with lateral force microscopy ͑LFM͒ as a function of sliding velocity and applied normal load in the presence of solvents ͑plasticizers͒. The objective of this study was to investigate whether decreases in the chain density of the SAMs caused maxima in the friction force to shift to higher sliding velocities; such a shift is indicative of shorter chain relaxation times in less dense, less ordered SAMs. Complete SAMs were formed from octadecyltrichlorosilane ͑OTS͒ and partial SAMs were formed from n-octadecylmethyldichlorosilane ͑2Cl͒ and n-octadecyldimethyldichlorosilane ͑1Cl͒, all on silicon/silicon dioxide substrates. With decreasing chain density, solvent partitioning into the monolayer should increase as OTSϽ2ClϽ1Cl. In butanol and pentanol, the maxima in the friction force shifted to higher sliding velocities with decreasing chain density, and the relaxation times calculated for the partial 2Cl films were an order of magnitude shorter than those for SAMs of OTS. For both SAMs of OTS and 2Cl films, maxima shifted to lower sliding velocities with increases in the applied normal load and with increases in the chain length n of the solvent. The higher compressibility of 2Cl films caused greater shifts in the maxima for similar increases in the applied normal load. The increase with n was consistent with both a mechanism of solvent partitioning controlled by the free volume distribution in the SAM and a mechanism of insertion. The relaxation times of the alkyl chains were related to a molecular model of energy dissipation involving the adsorption and desorption of the chain ends to and from the surface of the probe tip.

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“…The incident angle of the p-polarized infrared beam was 73.7 (Brewster angle) in order to eliminate the multiple reflection of the infrared beam within the silicon wafer substrate. 26,27 As substrates for the FT-IR measurements, silicon wafers with both surfaces polished were used to reduce the influence of fringes in the spectra. For IR spectra, 1024 scans were collected with a resolution of 0.5 cm À1 .…”

Section: Measurementsmentioning

confidence: 99%

Molecular Aggregation State of Surface-grafted Poly{2-(perfluorooctyl)ethyl acrylate} Thin Film Analyzed by Grazing Incidence X-ray Diffraction

Yamaguchi

Honda

Kobayashi

et al. 2008

Polym J

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Surface-initiated atom transfer radical polymerization of 2-(perfluorooctyl)ethyl acrylate on a flat silicon wafer was carried out to give poly{2-(perfluorooctyl)ethyl acrylate} (PFA-C 8 ) brush thin film with three different thicknesses of 4, 11, and 43 nm, respectively. The water contact angle of the PFA-C 8 brush surface was 120. The molecular aggregation state of the perfluoroalkyl (R f ) group of PFA-C 8 brush was analyzed by X-ray reflectivity (XR), wide-angle X-ray diffraction, and grazing incidence X-ray diffraction (GIXD) measurements. XR analysis revealed that R f groups at the air/brush interface formed a densely packed structure, while a relatively low-density region was generated at the brush/substrate interface. The peaks of in-plane GIXD for brush films with thicknesses of 11 and 43 nm were observed at q xy ¼ 12:5 nm À1 , which indicated that R f groups at the outermost surface oriented perpendicular to the surface of silicon substrate. In an out-of-plane diffraction profile of the 43 nm-thick PFA-C 8 brush film, peaks corresponding to a periodic length of the bilayer lamellae were observed. Therefore, R f groups of the thicker brush film were crystallized and formed ordered bilayer lamellar structure at the outermost surface. In contrast, no diffraction pattern was observed from the PFA-C 8 at a thickness of 4 nm by WAXD and GIXD. These results indicate that an amorphous layer was formed at the interface of the brush/substrate. The R f groups at the anchoring region of the brush could not form a sufficiently ordered structure due to immobilization of brush chain ends on the substrate. It was suggested that the R f groups in a PFA-C 8 brush thin film at the outermost surface aggregated in a different manner from those in the anchoring region.KEY WORDS: Perfluoroalkyl Acrylate / Polymer Brush / Water-Repellant Surface / X-Ray Reflectivity / Grazing Incidence X-ray Diffraction / Surface-initiated Polymerization / It has been well-known that polymers with perfluoroalkyl (R f ) groups show excellent chemical and thermal stability, nonadhesive properties, low friction coefficients, low surface free energy, and antifouling behavior. These properties of fluorinated polymers are primarily caused by unique C-F bonds which have a large binding energy and quite a low dielectric constant due to short bonding distance between carbon and fluorine atom with high electro negativity. However, the surface component, orientation packing, and end groups also affect the surface behavior of the polymer films.1-3 When the surface is uniformly covered with trifluoromethyl (CF 3 ) groups, 4 excellent water repellency and a very low energy surface can be achieved. 5 In the case of poly(fluoroalkyl acrylate)s with long R f groups, the molecular aggregation state of the R f groups at the side chains affects the surface wettablity. 6,7 We have recently reported the relationship between the molecular aggregation states and the water repellency of poly(perfluoroalkyl acrylate) (PFA-C y , where y is the number of fluoromethylene...

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Molecular Aggregation State of n-Octadecyltrichlorosilane Monolayer Prepared at an Air/Water Interface

Cited by 91 publications

References 18 publications

Engineering Silicon Oxide Surfaces Using Self‐Assembled Monolayers

Engineering Silicon Oxide Surfaces Using Self‐Assembled Monolayers

The effect of chain density on the frictional behavior of surfaces modified with alkylsiloxanes and immersed in n-alcohols

Molecular Aggregation State of Surface-grafted Poly{2-(perfluorooctyl)ethyl acrylate} Thin Film Analyzed by Grazing Incidence X-ray Diffraction

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