Abstract
In this work we have examined the use of plasticiser-free polymeric films incorporating a proton selective chromoionophore for optical pH sensor. Four types of methacrylic-acrylic copolymers containing different compositions of n-butyl acrylate (nBA) and methyl methacrylate (MMA) were synthesised for use as optical sensor films. The copolymers were mixed with appropriate amounts of chromoionophore (ETH5294) and a lipophilic salt before spin coated on glass slides to form films for the evaluation of pH response using spectrophotometry. Co-polymer films with high nBA content gave good response and the response time depended on the film thickness. A preliminary evaluation of the optical films of high nBA content with pHs from 2 - 14 showed distinguishable responses from pH 5 - 9. However, the adhesion of the pH sensitive film was good for copolymers with higher content of MMA but not for films with high nBA.
Highlights
Polymers have been given both theoretical interest and practical application in the field of sensor technology in the last decade
The high amount of n-butyl acrylate (nBA) in the copolymer MB19 obviously caused the polymer to be very soft and weak, this may reduce the adhesion on the glass substrate
The softness and elasticity of the non-plasticised based polymers is important in providing flexibility to the chromoionophore in the extraction of H+ by complexation processes[6]
Summary
Polymers have been given both theoretical interest and practical application in the field of sensor technology in the last decade. Optical sensor based on plasticised PVC membranes to detect ions have been long developed. The application of this class of plasticiser-free polymers has been extended to optical ion sensors, membranes based on cross-linked dodecyl acrylate[7] and decyl methacrylate[8].
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