(a) Reservoirs and substrate were placed in a Teflon insert that confined chlorosilane movement to a small gap (≈1.5 mm) above the substrate surface. (b) The insert was loaded into the deposition chamber and deposition occurred under dynamic vacuum. Vacuum connections could be made at one or both sides of the chamber – illustrated here with the vacuum connection on the right side of the chamber open and the left side closed. (c) Schematic representation used to describe setup specifics (reservoir sizes, positions, vacuum direction, and materials) discussed in this work. (d) Photograph of the setup shown schematically in (c). Adapted with permission from J. N. L. Albert, M. J. Baney, C. M. Stafford, J. Y. Kelly, and T. H. Epps III, ACS Nano 3, 3977 (2009). Copyright 2009 American Chemical Society (Ref. 14).
Development of contact angle/composition correlation for benzyl/aceto (a–c), benzyl/fluoro (d–f), and benzyl/n-butyl (g–i) gradients. (a, d, and g) XPS C1s spectra for pure component monolayers. Data along the y-axis of the XPS spectra are given in counts per second (CPS). Data are shown with darker lines (“CPS”), and the overall fits to the data are shown with lighter lines (“fit”). The benzyl silane (blue) data were fit using three Gaussian/Lorentzian curves (not shown) representing a shake-up peak (≈292 eV), C–O binding due to adventitious carbon (≈286 eV), and C–C binding (≈285 eV). The aceto silane (orange) data were fit using three Gaussian/Lorentzian curves (not shown) representing C=O (≈289 eV), C–O (≈286 eV), and C–C (≈284 eV) binding to generate the overall fit. The fluoro silane data were fit using four Gaussian/Lorentzian curves (not shown) representing – CF3 (≈294 eV), –CF2 (≈292 eV), and C–C (two curves ≈285–286 eV) binding to generate the overall fit. The n-butyl silane data were fit using one Gaussian/Lorentzian curve representing C–C (≈285 eV) binding to generate the overall fit. (b, e, and h) Examples of fitting gradient C1s spectra using the two pure component monolayer fits. (c, f, and i) Correlations between composition (mole fraction non-benzyl silane) and diiodomethane contact angle.
(a) Effect of changing the benzyl silane reservoir size on gradient profiles (keeping 12.7 mm (1/2 in.) diameter methacryl silane reservoir). (b) Effect of changing methacryl silane reservoir size on gradient profiles (keeping 9.5 mm (3/8 in.) diameter benzyl silane reservoir). (c) Comparison of setups with the same B/M area ratio: B/M = 1 (purple circles) and B/M = 0.25 in (green squares) [see Table II].
(a) Effect of reservoir placement on gradient profiles. The reservoir sizes were fixed at 12.7 mm (1/2 in.) diameter methacryl silane and 9.5 mm (3/8 in.) diameter benzyl silane, and dynamic vacuum was applied to the benzyl silane reservoir side. (b) Effect of reservoir placement when two differently sized (12.7 mm (1/2 in.) and 6.35 mm (1/4 in.)) reservoirs of the benzyl silane were used.
Effect of vacuum application on gradient profiles. The reservoir sizes were fixed at 12.7 mm (1/2 in.) diameter methacryl silane and 9.5 mm (3/8 in.) diameter benzyl silane and both reservoir positions were fixed at 4.5 cm.
Effect of chlorosilane volatility on gradient profile. Reservoir sizes were fixed at 9.5 mm (3/8 in.) diameter non-benzyl silane and 9.5 mm (3/8 in.) diameter benzyl silane. Reservoir positions were fixed at 4.5 cm, and dynamic vacuum was applied to the benzyl silane reservoir side. Relative volatilities of the chlorosilanes from Table I were as follows: methacryl < benzyl ≈ aceto < fluoro < n-butyl.
(a) Schematic of optimized vapor deposition setups for benzyl/methacryl, benzyl/aceto, benzyl/fluoro, and benzyl/n-butyl gradients. The chlorosilane names are abbreviated as follows: A – aceto silane, B – benzyl silane, F – fluoro silane, M – methacryl silane, and nB – n-butyl silane. (b) The optimized gradient composition, water contact angle, diiodomethane contact angle, and surface energy profiles.
Boiling points of chlorosilanes and pure component monolayer surface energies.
Set ups with equivalent surface area ratios of benzyl silane to methacryl silane (B/M).
Article metrics loading...
Full text loading...