Preparation of Dehydroabietyl Polyethylene Glycol Aldehyde Modified Hydroxyethyl Chitosans and their Physicochemical Properties

A series of polymeric surfactants based on monodehydroabietyl polyoxyethylene(5) ether (DHA(EO)(5)H) and hydroxyethyl chitosan (HEC) were prepared through a three-step process. First, DHA(EO)(5)H was oxidized using activated MnO2 and transformed into dehydroabietyl polyethylene glycol(5) aldehyde (DHA(EO)(4)CH2CHO). Then, the DHA(EO)(4)CH2CHO was reacted with HEC and converted into Schiff-base. Finally, the polymeric surfactant, DHA(EO)(4)CH2CHO modified HEC (DHA(EO)(4)CH2CHO-m-HEC), was obtained by reducing the Schiff-base with sodium borohydride. The grafting degree (DG) of DHA(EO)(4)CH2CHO substitution onto HEC for DHA(EO)(4)CH2CHO-m-HECs was determined using elemental analysis (EA), and the surface activities and foam performance of DHA(EO)(4)CH2CHO-m-HECs in aqueous solution were investigated respectively. The emulsifying capacities of DHA(EO)(4)CH2CHO-m-HECs were evaluated according to the stability times of emulsion composed of water and liquid paraffin. The experimental results showed the DG could have significant influence on the critical micelle concentration (cmc) of DHA(EO)(4)CH2CHO-m-HECs and their surface tensions at cmc (gamma(cmc)), but nearly no effect on their minimum surface tensions (gamma(min)) in aqueous solution. Among the synthetic polymeric surfactants in this investigation, DHA(EO)(4)CH2CHO-m-HEC with DG of 56.95% exhibited the best emulsification and foam properties.