POLYELECTROLYTE PECTIN-POLYETHYLENEIMINE COMPLEX AND TERNARY POLYELECTROLYTE-METAL COMPLEXES BASED ON IT: A MAS SPECTROMETRY STUDY

Abstract

A polyelectrolyte complex (PEC) of pectin (polyanion) and polyethyleneimine (polycation) at an equimolar ratio of carboxylic to amino groups was synthesized. Based on it, polyelectrolyte-metal complexes (PEMC) were prepared by adsorption of copper and silver ions from 0.1 M aqueous solutions of CuSO4 and AgNO3 salts. The starting materials (pectin, polyethyleneimine), polyelectrolyte complexes, and polyelectrolyte-metal complexes with Cu2+ and Ag+ were characterized by pyrolysis mass spectrometry (PMS). The PMS results (total ionic current, amount of volatile products, their specific intensity) indicate significant differences in the behavior of the studied objects during pyrolysis and confirm the formation of a polyelectrolyte complex between pectin and polyethyleneimine. It was found that PEC is thermally less stable than the starting materials (pectin and PEI), probably due to electrostatic interaction and corresponding redistribution of electron density between atoms in the macromolecules of pectin and PEI due to complexation. Differences in the thermal behavior of copper- and silver-containing PEMC are caused by complexation processes in these compounds and the different chemical structures of the obtained samples. The kinetics of the total ionic current during the pyrolysis of pectin-PEI complexes with Cu2+ at a temperature of 170 °С and with Ag+ at a temperature of 150 °С was studied and it was found that PEMC are thermostable for 30 min at the given temperature. Such PMS results provide evidence for the possibility of forming copper- and silver-containing nanocomposites by thermochemical reduction of Cu2+ or Ag+ ions in the studied polyelectrolyte-metal complexes based on PEC pectin-polyethyleneimine. The previously proposed mechanism of thermochemical reduction of Cu2+ and Ag+ ions during the synthesis of the corresponding nanocomposites was confirmed.