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Near-Infrared pH Sensor based on SPEEK-Polyaniline Polyelectrolyte Complex
1  Department of Chemical and Process Engineering Technology, Jubail Industrial College, Jubail Industrial City 31961, Saudi Arabia

Published: 31 August 2018 by MDPI in 1st International Online Conference on Nanomaterials session Materials

Polyelectrolyte complex (PEC) membrane based on sulfonated poly(ether ether ketone) and polyaniline (SPEEK-PANI) was developed for pH sensing application. Aniline was polymerized in the presence of SPEEK membrane by using in situ chemical oxidative polymerization to yield an ionically crosslinked SPEEK-PANI membrane. The fabricated membrane exhibited sensitivity in the physiological pH range of 2-8. The PEC membrane pH sensor showed good absorption properties in the near-infrared region (NIR). The membrane showed fast response during de-doping process (< 30 s), while longer response times are essential for doping process from low pH region to neutral or basic pH region, which is attributed to the presence of ionic interaction in the self-doped polyaniline structure. SPEEK-PANI membrane exhibited slightly higher water uptake as compared to neat SPEEK membrane. The membrane exhibited good stability as it was stored in 1M HCl solution for more than 2 years without physical or visual deterioration. A preconditioning step in 1 M HCl ensures obtaining reproducible results and allows for the pH sensor to be used repeatedly.

Keywords: polyelectrolyte complex; pH sensor; Near-Infrared; polyaniline; SPEEK
Comments on this paper
Ana Maria Diez-Pascual
Comments on the paper
I really enjoy reading the paper. One question, what is the advantage of the SPEEK-PANI membranes compared with pristine SPEEK ones?

Nedal Abu-Thabit
Reply to Dr. Ana Maria Diez Pascual
Dear Ana,

I'm so happy to read your above comment!

Pristine SPEEK membranes can not be used for pH sensing as they are not pH-sensitive. However, they have been used for humidity sensing applications.
In the current study, I have tried to see what is the effect of immobilization of Polyaniline (pH-sensitive polymer) into SPEEK membrane (anionic polyelectrolyte solid support). As opposite to our previous work with polysulfone-coated polyaniline, the doping and de-doping process is not easy due to compexation between the SPEEK-PANI polyelectrolytes.

In addition, SPEEK-PANI Polyelectrolyte complex has been used as PEM for fuel cells applications, as it improved the water retention capability and the mechanical stability of the membranes due to flexible crosslinks.

The concept of polyelectrolyte complexation is very interesting and have a wide range of applications. The PEC can be done alternatively by using LbL self-assemble process. I have tried this process with the same work presented in this conference, but the stability of the formed PANI/SPEEK multilayers was not good for pH-sensing.
Monica Singh
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Omari Leroy
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