Qualitative and Semiquantitative Determination of the Atomic and Molecular Tungsten Distributions in Hybrid Hydroxyurethanes-Poly(dimethylsiloxane) Films Containing Phosphotungstates ([PW12O40]3-)

Orlando Elguera Ysnaga; Kelen M F Rossi de Aguiar; Cibele Bugno Zamboni; Wagner Luiz Polito; Ubirajara P Rodrigues-Filho

doi:10.1177/0003702820945018

Qualitative and Semiquantitative Determination of the Atomic and Molecular Tungsten Distributions in Hybrid Hydroxyurethanes-Poly(dimethylsiloxane) Films Containing Phosphotungstates ([PW₁₂O₄₀]^3-)

Appl Spectrosc. 2020 Dec;74(12):1515-1529. doi: 10.1177/0003702820945018. Epub 2020 Oct 12.

Authors

Orlando Elguera Ysnaga¹, Kelen M F Rossi de Aguiar², Cibele Bugno Zamboni³, Wagner Luiz Polito¹, Ubirajara P Rodrigues-Filho¹

Affiliations

¹ Institute of Chemistry of São Carlos, University of São Paulo (IQSC-USP), São Carlos, Brazil.
² Federal University of Technology-Paraná (UTFPR), Toledo, Brazil.
³ Nuclear and Energetic Research Institute (IPEN/CNEN-SP), São Paulo, Brazil.

PMID: 32638630
DOI: 10.1177/0003702820945018

Abstract

In this study, hybrid poly(dimethylsiloxane)-derived hydroxyurethanes films (PDMSUr-PWA) containing phosphotungstic acid (H₃PW₁₂O₄₀/PWA) were characterized using field emission gun scanning electron microscopy (FEG-SEM), in attenuated total reflectance Fourier transform mid-infrared mode (ATR FT-MIR), and analyzed using synchrotron radiation micro-X-ray fluorescence (SR-μXRF), synchrotron radiation grazing incidence X-ray fluorescence (SR-GIXRF), laser-induced breakdown spectroscopy (LIBS), and instrumental neutron activation analysis (NAA) in order to correlate the distribution patterns of tungsten and properties of PDMSUr-PWA films. PDMS constitute elastomers with good mechanical, thermal, and chemical (hydrophobicity/non-hygroscopy) resistance. Currently, products based on urethanes (e.g., polyurethanes) are widely used in many applications as plastics, fiber-reinforced polymers, high-performance adhesives, corrosion-resistant coatings, photochromic films, among others. The possibility to combine inorganic and organic components can produce a hybrid material with unique properties. PWA has an important role as agent against the corrosion of steel surfaces in different media, besides exhibiting amazing catalytic and photochromic properties in these films. PWA kept its structure inside of these hybrid films through interactions between the organic matrix of PDMSUr and silanol from the inorganic part (organically modified silica), as was shown using ATR FT-MIR spectra. The FEG-SEM/SR-μXRF/wide-angle X-ray scattering (WAXS)/X-ray diffraction (XRD)/energy dispersive X-ray results proved the presence of PWA in the composition of domains of PDMSUr-PWA films. At PWA concentrations higher than 50 wt%/wt, tungsten segregation across the thickness is predominant, while that at PWA concentrations lower than 35 wt%/wt, tungsten segregation at surface is predominant. Inhomogeneities in the tungsten distribution patterns (at micrometric and millimetric level) may play an important role in the mechanical properties of these films (elastic modulus and hardness).

Keywords: Hydroxyurethanes–poly(dimethylsiloxane) films; LIBS; NAA; PDMSUr-PWA films; SR-μXRF; hybrid materials; instrumental neutron activation analysis; laser-induced breakdown spectroscopy; synchrotron radiation micro-X-ray fluorescence.