Stability and thermodynamic parameters of interpolymer complexes of acrylamide/alkyl acrylate copolymers with poly(ethyleneimine): effects of microstructure and alkyl substituents of copolymers on interpolymer association

Abstract

Acrylamide/ethyl acrylate (A/E) and acrylamide/butyl acrylate (A/B) copolymers of different compositions were prepared in solution by free radical polymerization. The copolymer compositions were determined from the nitrogen content in the copolymers. Interpolymer complexes of both A/E and A/B copolymers with polyethyleneimine (PEI) were prepared in DMF-water (80: 20 v/v). The stability constants and related thermodynamic parameters (e. g., ΔG 0 . ΔH 0 and ΔS 0 ) of the interpolymer complexes were determined using Osada's method. These parameters were correlated with the sequence distribution of monomer units in the copolymer chains which were obtained from 13 C{ 1 H} NMR spectroscopy. The size of the alkyl group and the microstructure of the copolymers influence the association between the copolymer and PEI, which is reflected in the stability of the interpolymer complexes.