Effect of metal ions and pH values on the conformational transition of the copolymer chain in aqueous solutions

Abstract

A novel salts- and pH-responsive copolymer, poly(acrylic acid-co-ethyl 1-(4-chlorophenyl)-5-acrylamino-1,2,3-triazol-4-carboxylate), poly(AA-co-ECATC), was prepared by radical polymerization in methanol at room temperature with L-ascorbic acid (Vc) and peroxide hydrogen (H2O2) as initiators. The copolymer was characterized by Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). The copolymer possessed excellent fluorescence properties. The effects of metal ions with different charges, radius and outer-layer electron constructions and pH values on the conformation transition of copolymer chains were systematically investigated by the fluorescence intensity and the fluorescence anisotropy. It was found that fluorescence intensity and fluorescence anisotropy curves waved with the change of metal ions concentrations and pH values. Additionally, FTIR Subtraction spectroscopy was also carried out to confirm our results. The work provided a theory basis for the study of salts- and pH-sensitive smart hydrogels, which were always used in the slow- or controlled-release drugs. © 2007 Wiley Periodicals, Inc.