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Open AccessArticle

PDMS Based Hybrid Sol-Gel Materials for Sensing Applications in Alkaline Environments: Synthesis and Characterization

1
Centro de Química, Campus de Gualtar, Universidade do Minho, 4710-057 Braga, Portugal
2
ISISE, Departamento de Engenharia Civil, Escola de Engenharia, Campus de Azurém, Universidade do Minho, 4800-058 Guimarães, Portugal
*
Authors to whom correspondence should be addressed.
Polymers 2020, 12(2), 371; https://doi.org/10.3390/polym12020371
Received: 29 November 2019 / Revised: 10 January 2020 / Accepted: 16 January 2020 / Published: 7 February 2020
(This article belongs to the Special Issue Organic-Inorganic Hybrid Materials)
Nowadays, concrete degradation is a major problem in the civil engineering field. Concrete carbonation, one of the main sources of structures’ degradation, causes concrete’s pH to decrease; hence, enabling the necessary conditions for corrosion reinforcement. An accurate, non-destructive sensor able to monitor the pH decrease resistant to concrete conditions is envisaged by many researchers. Optical fibre sensors (OFS) are generally used for concrete applications due to their high sensitivity and resistance to external interferences. Organic-inorganic hybrid (OIH) films, for potential functionalization of OFS to be applied in concrete structures, were developed. Polydimethylsiloxane (PDMS) based sol-gel materials were synthesized by the formation of an amino alcohol precursor followed by hydrolysis and condensation. Different ratios between PDMS and (3-aminopropyl)triethoxysilane (3-APTES) were studied. The synthesized OIH films were characterized by Fourier-transformed infrared spectroscopy (FTIR), UV–Vis spectroscopy, electrochemical impedance spectroscopy (EIS) and thermogravimetric analysis (TGA). The OIH films were doped with phenolphthalein (Phph), a pH indicator, and were characterized by UV–Vis and EIS. FTIR characterization showed that the reaction between both precursors, the hydrolysis and the condensation reactions occurred successfully. UV–Vis characterization confirmed the presence of Phph embedded in the OIH matrices. Dielectric and thermal properties of the materials showed promising properties for application in contact with a high alkaline environment. View Full-Text
Keywords: sol-gel; PDMS; pH; hybrid; phenolphthalein sol-gel; PDMS; pH; hybrid; phenolphthalein
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MDPI and ACS Style

Sousa, R.P.C.L.; Ferreira, B.; Azenha, M.; Costa, S.P.G.; Silva, C.J.R.; Figueira, R.B. PDMS Based Hybrid Sol-Gel Materials for Sensing Applications in Alkaline Environments: Synthesis and Characterization. Polymers 2020, 12, 371.

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