Polyvinylbenzyl Tris-Aminodicarboxylate Microspheres for the Optical Sensing of Cu²⁺ Ions

Abstract

In this work, a tris(2-aminoethyl)aminodicaboxylate functionality was substituted for the chloride of polyvinyl - benzyl chloride (PVBC) which was lightly cross-linked (2%) with divinyl benzene. The resulting derivatized po lymer microspheres were embedded in a hydrogel matrix of poly vinyl alcohol cross-linked with glutaraldehyde to produce a sensing membrane. The latter responded selectively to Cu 2+ solutions of different concentration ranges (1 × 10 -4 M to 1 × 10 -6 M). The response is based on the interaction between the metal cations and the negatively charged deprotonated dicarboxylate functional group, which led to neutralization of the charges. As a result, an increase in the turbidity of the sensing membrane occurred which is attributed to a change in the re fractive index of the derivatized polymer microspheres relative to that of the hydrogel. The change in the turbid ity of the sensing membrane was measured as absorbance using a conventional spectrophotometer. It was found that Cu 2+ ions bind to the aminodicarboxylated-polymer with a formation constant, K f , of 1 × 10 5 M -1 . SEM, Eds and IR analyses were performed on the aminodicarboxylated microspheres and their Cu 2+ complex.