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

Abstract

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