Leaching-Resistant Self-Plasticized Poly(Vinyl Chloride) (PVC) as a Matrix for Ion-Selective Electrodes

Polymer-based ion-selective electrodes typically rely on plasticized polymeric membranes to incorporate functional sensing components, but leaching of plasticizer into solution can negatively affect the response stability, operability, and overall lifetime of these sensors. Moreover, plasticizer loss can result in cytotoxicity, which is especially undesirable in wearable sensors and bioanalytical probes, requiring strict regulation and monitoring of the plasticizers used. To help overcome this challenge, a new class of self-plasticized poly-(vinyl chloride) (PVC) derivatives was synthesized here by grafting a plasticizer-like group onto azide-modified PVC using a highly efficient azide-alkyne Huisgen cycloaddition "click" reaction. The resulting polymer is naturally elastic and malleable that allows for the dissolution of sensing components and ion diffusion through the selective membrane, overcoming the need for an additional plasticizer. When applied to a library of ions (Ca²⁺, H⁺, K⁺, NO₃ ^-), the resulting membrane electrodes demonstrated promising stability and lifetime with an overall drift of 0.3 mV for the calcium-selective electrode over a testing period of 5 days. This synthetic approach provides a promising pathway for developing plasticizer leak-free, high-performance, and operationally stable sensors.