Polyethyleneimine derivatives as catalysts : dye-binding capacity and reactivity are not diminished on extensive internal cross-linking of the polymers

Polyethyleneimine molecules alkylated with naphthylmethyl bromide and benzyl bromide and internally cross-linked by reaction with alkyl dihalides have binding capabilities enhanced by up to twofold. The modified and cross-linked polyethyleneimines bind large numbers of methyl orange dye molecules; since no evidence is found for dye stacking the cross-linked polyethyleneimine is considered to retain the flexibility of the native material. Increasing the cross-linking percentage from 0 to 20% of the available nitrogen causes a modest twofold increase in binding strength; cross-linking of polyethyleneimine in the presence of methyl orange dye produces a polymer which has doubled binding capacity for this dye than has the polymer cross-linked in the absence of added dye. Cross-linking does not reduce the number of primary amines in the alkylated polyethyleneimine available for reaction with Cu (1) ions or with 2,4,6-trinitrobenzenesulphonate anion. The reactivity of the cross-linked polymers with 4-nitrophenyl esters is not reduced below that of the native polyethyleneimine.