Qualitative and Semiquantitative Determination of Bromine in Hybrid Hydroxyurethanes-Poly(dimethylsiloxane) Films Containing Phosphotungstates ([PW&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;40&lt;/sub&gt;]&lt;sup&gt;3-&lt;/sup&gt;)

Orlando Elguera Ysnaga

doi:10.11648/j.ep.20200402.11

Abstract

In this study, the complex hybrid materials based on hybrid poly(dimethylsiloxane)-derived hydroxyurethanes films (PDMSUr-PWA) containing phosphotungstic acid (H3PW12O40/PWA) and Bromine were analyzed by laboratory XRF (EDXRF, WDXRF), Synchrotron Radiation Micro X-ray Fluorescence (SR-μXRF), and Volumetric analysis, in order to correlate the distribution patterns and composition of Bromine with their respective properties and potential applications. Recently, the characterization and analysis of PDMSUr-PWA films (without consider Bromine) was reported in order to correlate structure, compositions and properties. SR-μXRF maps provide indicatives of the possible inter-elemental interactions Bromine-Silicon-Tungsten. There is segregation of Bromine at surface and through the thickness of PDMSUr-PWA films. These films possess hydrophobicity and non-hygroscopic properties, which makes potential candidates for high-performance adhesives, corrosion-resistant coatings of steel and titanium alloys surfaces in different media. The presence of Bromine (element provided from tetraethylammonium bromide in previous steps of elaboration of PDMSUr-PWA films) could contribute with their corresponding adhesive, thermal-insulator, and anti-corrosive properties. Functional materials as PDMSUr-PWA films present easy processing, excellent toughness and durability. Nowadays, Polyurethane (PU) coatings are very useful in many sectors due to their excellent mechanical properties. Nonetheless, one limitation is their thermal stability, which can be improved by insertion of poly(dimethylsiloxane) (PDMS) segments. The interesting properties of PDMS are of significance for applications as adhesives and at the aerospace industry. The films containing 1%, 35%, 40-50% PWA are candidates as anticorrosive coatings and as inert materials under the presence of polar chemical reagents, based on the significant Bromine presence at surface. The films containing 25% and 55% PWA would be suitable for thermal insulators, based on the significant Bromine presence at thickness. PDMSUr-PWA films can constitute systems for the storage of energy based on the synergy of their potential applications as Proton exchange membrane fuel cells (PEMFCs) and also as H2-Br2 multiple micro-fuel cells. PEMFCs have great attention in scientific and industrial fields based on energetic and environmental aspects mainly. PEMFCs based on PDMSUr-PWA films could exhibit high chemical and mechanical stabilities. The hydrogen bromine (H2-Br2) electrochemical systems constitute promising candidates as generation and storage devices of energy due to their high energy capacities and conversion efficiencies, as also their low costs. More in depth studies are necessary in order to analyze the different chemical forms of Bromine present (atomic, ionic and/or molecular) in the three-dimensional network constituted by silicates and phosphotungstates, as also the characterization of their local chemical and electrochemical environment.

Highlights

Functional materials present easy processing, excellent toughness and durability
This study based on multiple analyses (EDXRF, Wavelength Dispersive X-ray Fluorescence (WDXRF), SR-μXRF and Volumetric titration) has evidenced the presence of Bromine (Br) in the complex system that constitute PDMSUr-PWA films
More in depth studies are necessary in order to know if the Bromine is trapped in the three-dimensional of silicates and phosphotungstates network as atomic, ionic and/or molecular form

Summary

Introduction

Functional materials present easy processing, excellent toughness and durability. Hybrid (organic–inorganic entities mixed at molecular level) materials meet these conditions, which are classified according to the interactions between organic and inorganic parts as Class-I and Class-II. From Heteropoly acids (HPAs) immobilized, especially PWA (e.g in PDMSUr matrix), can be made PEMs with high proton conductivities and performances at different temperature levels [10, 12, 14, 15] For this reason, membranes based on composite materials containing HPAs, immobilized in PDMS/PDMSUr matrices, can constitute proton conductive materials for Engineering Physics 2020; 4(2): 19-36 operation at elevated temperatures. Membranes based on composite materials containing HPAs, immobilized in PDMS/PDMSUr matrices, can constitute proton conductive materials for Engineering Physics 2020; 4(2): 19-36 operation at elevated temperatures It is crucial for PEMs based on PWA the understanding of mechanisms for proton transport (facilitated by water molecules from heteropolyanion), and of their conductivity for the development of fuel cells [14, 15]. In PDMSUr-PWA films, the silanol groups can act as counter-ions for PWA ions, producing species e.g. (≡SiOH2+) x (H2PW12O40-) y [9, 11]

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