title: Fabrication and Characterization of Cross-Linked Organic Thin Films with Nonlinear Mass Densities.
abstract: The preparation of urea (bonded) cross-linked multilayer thin films by sequential deposition of bifunctional and tetrafunctional molecular building blocks is demonstrated. Multilayer growth as a function of deposition cycles was inspected using UV-vis absorption spectroscopy. From infrared results, three characteristic infrared bands of amide I, amide II, and asymmetric νa(N-C-N) stretching confirmed the formation of polyurea networks by alternate dipping into solutions of amine and isocyanate functionality monomers. The deconvoluted component of the C 1s and N 1s spectra obtained by X-ray photoelectron spectroscopy shows clear evidence of stable polyurea networks. The enhancement of structural periodicity with film growth was demonstrated by grazing-incidence small-angle X-ray scattering measurements. The thin film near the substrate surface seems to have an amorphous structure. However, molecular ordering improves in the surface normal direction of the substrate with a certain number of deposited layers. Constant mass density was not observed with deposition cycles. The mass density increased up to 16% within deposited layers from proximate layers to those extending away from the substrate surface. This difference in the packing density might derive from the different degrees of cross-linking among layers proximate to the substrate surface and extending away from the substrate surface.
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology , 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan.
authors.forename: Md A
authors.initials: MA
authors.lastname: Rashed
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology , 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan.
authors.forename: Salinthip
authors.initials: S
authors.lastname: Laokroekkiat
authors.affiliation: Department of Molecular Design & Engineering, Graduate School of Engineering, Nagoya University , Furo-cho, Chikusa, Nagoya 464-8603, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Hara
authors.affiliation: Nagoya University Venture Business Laboratory, Nagoya University , Furo-cho, Chikusa, Nagoya 464-8603, Japan.
authors.forename: Shusaku
authors.initials: S
authors.lastname: Nagano
authors.affiliation: School of Materials Science, Japan Advanced Institute of Science and Technology , 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nagao