Synthesis and characterisation of hydrophobic modified polyacrylamide

Polyacrylamide has been modified hydrophobically with low amounts of N-alkyl groups by a transamidation method, using alkylamines. The amide group in the polymer backbone has been N-substituted in water solutions, where the substituting amine is water-soluble. The alkyl groups include N-alkyl (up to octyl), N,N-diethyl, N,N-dipropyl, N-isopropyl, N,N-diisopropyl and N-cyclohexyl groups. This transamidation method is more convenient compared with the traditional micellar copolymerisation methods and the direct method using alkyl halide substitution. However, a limitation of the method is due to the failure to achieve substitution of highly hydrophobic groups such as dodecyl. The mutual insolubility of dodecylamine and the potential substituted product, with N-dodecyl substitution of polyacrylamide, makes it impractical to carry out the reaction in water. Other mixed solvents were used for the amine substitution, including water with dimethylsulfoxide and ethylene glycol, without transamidation occurring, since these solvents decreased the solubility of polyacrylamide. The NMR and IR spectra of modified polyacrylamides are reported. The mechanism of the reaction under acid- and base-catalysed situations is discussed.