Article Synopsis
- The study demonstrates the preparation of cross-linked multilayer thin films using bifunctional and tetrafunctional molecular building blocks through sequential deposition.
- UV-vis absorption spectroscopy and infrared results confirm the formation of polyurea networks, marking the successful creation of these films.
- X-ray photoelectron spectroscopy indicates stable polyurea networks, while grazing-incidence small-angle X-ray scattering shows variations in structural ordering and mass density with film growth, suggesting different degrees of cross-linking near the substrate.
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Article 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.
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| http://dx.doi.org/10.1021/acs.langmuir.6b00540 | DOI Listing |
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