The sulfonation of polyvinyl chloride: Synthesis and characterization for proton conducting membrane applications

• Developed a sulfonation process for PVC that does not alter existing morphology membrane.
• Sulfonated PVC (PVCs) and unmodified PVC load with acid to mimic conditions for sensor deployment.
• Acid loaded PVCs had significantly larger proton conductivity than acid-loaded PVC.
• Increased conductivity is due to PVCs having increased electrolyte uptake over unmodified PVC.

Sulfonated poly-vinyl chloride (PVCs) membranes were synthesized first using an ethylenediamine solution to aminate the porous free-standing poly-vinyl chloride (PVC) membrane. This modified PVC was then reacted with sulfuric acid to form the PVCs material. The reaction time was varied to give PVCs materials of different degrees of sulfonation (DS). The membranes were characterized with FTIR and elemental analysis to confirm the presence of a –SO3H group. SEM was used to ensure the morphology had not changed during the reaction. Water-uptake and proton conductivity were measured and it was found that as the reaction time increased, both conductivity and water-uptake of the membranes increased compared to the unmodified PVC material. This study demonstrates a novel technique to impart increased water-uptake and proton conductivity to a PVC polymer without destroying the pre-existing membrane morphology.

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