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

Rui P C L Sousa,Bárbara Ferreira,Susana P G Costa,Miguel Azenha,Rita B Figueira,Carlos J R Silva

doi:10.3390/polym12020371

Abstract

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.

Highlights

The sol-gel process is a synthetic method that allows producing organic-inorganic hybrid (OIH)materials [1,2]
UV–Vis characterization confirmed the presence of Phph embedded in the OIH matrices
((a) and (b)), from a sample during synthesis after min of precursors addition and the final in the polymeric matrix

Summary

Introduction

The sol-gel process is a synthetic method that allows producing organic-inorganic hybrid (OIH)materials [1,2]. OIH sol-gel materials can be doped with several species, such as corrosion inhibitors [17], electrolytes (to produce high conductivity films) [18], pharmaceutical drugs or other biomolecules [19]. These materials can be doped with chemosensors, allowing them to obtain a polymeric matrix with sensing abilities [20,21,22]. A chemosensor is a molecule that is sensitive to the presence of a certain analyte and provides a detectable change in a signal, transducing

Methods

Results

Conclusion