Cation exchange resin from phosphorylated N-vinylcarbazole formaldehyde copolymer

Crosslinked copolymers of N-vinylcarbazole and poly N-vinylcarbazole) and formaldehyde have been phosphorylated using PCl₃ and anhydrous AlCl₃ under different conditions. The cation exchange resins, thus obtained, have been characterized by elemental analyses, evaluation of total ion-exchange capacities and salt-splitting capacities, pH metric titration behavior, and IR analysis. The phosphorylated resin exhibites significantly better thermal stability than the corresponding sulfonated N-vinylcarbazole–formaldehyde cation exchange resin or the unmodified N-vinylcarbazole–formaldeyde copolymer, as well as the phosphorylated poly(N-vinylcarbazole). The phosphorylated resins also behave as polymeric dyes with pH dependent color change. Possible explanations for color change and ion-exchange capacity differences have been attempted on the basis of the structural characteristics of the resins.