Effect of the molecular character and extent of crosslinking on the reactivity of attached amino groups in crosslinked polyacrylamide gels

Abstract

The dependence of the reactivity of the attached amino groups in crosslinked polyacrylamide gels on the extent of crosslinking and the molecular character of the crosslinks has been studied. Acrylamide has been copolymerized with N, N'-methylene-bis-(acrylamide) (NNMBA), tetraethyleneglycol diacrylate (TEGDA) and divinyl benzene (DYB) in different proportions to afford crosslinked polyacrylamide gels of varying nature and extent of crosslinking. These gels have been functionalised with amino groups by treating with excess ethylenediamine. The extent of amino functionalisation is found to be dependent on the nature and degree of crosslinking. The reactivity of amino groups in these polyacrylamide gels has been investigated by following the course of aminolysis of <em>p</em>-nitrophenyl acetate with these resins. These studies reveal a significant influence of the nature and extent of crosslinking on the aminolysis reaction. The polarity of the crosslinking agent and its molar percentage affect the extent of swelling and solvation which are decisive in the facilitation of the aminolysis of the <em>p</em>-nitrophenyl active ester.