Hydrogels formed by l-histidine derivatives with highly selective release for charged dyes

The amphiphilic derivatives of l-histidine with different alkyl chains, NIPCA, UIPCA, and TIPCA, have been designed and their self-assembly behaviors with citric acid were investigated. All l-histidine derivatives can form hydrogels with citric acid, and exhibit the increasing gelation ability and mechanical strength with the increasing chain length. The gelation ability is considered to be affected by the synergistic effect of electrostatic interaction, hydrogen bonding and hydrophobic interaction. The hydrogels exhibit excellent releasing selectivity for charged dyes in aqueous solution, enlightening people to utilize this kind of hydrogels as intelligent carriers to separate the mixtures of charged dyes.