| In this paper, a new type of amphiphilic chitosan (CS) derivative was synthesized, andthe solution behavior and application was investigated. Firstly, CS was acylated with succinicanhydride to synthesize hydrophilic succinyl chitosan (SCS). Then SCS was hydrophobicallymodified by using Lauroyl chloride to prepare lauroyl succinyl chitosan (LSCS). Thestructure of product was characterized by FTIR and1H-NMR spectrum. In the hydrophilicmodification, Zeta potential and isoelectric point of SCS decreased with the mole ratio ofchitosan/succinic anhydride increasing, that indicated the succinyl substitution increased.Inthe hydrophobic modification, with the condition of SCS/lauroyl chloride mole ratio1:2,reaction-time7h, volumn of NaOH (0.1mol/L)4mL, the LSCS contained more alkyl chainsand the solution had a higher viscosity.The solution behavior of LSCS was investigated by turbidity method, fluorescentmolecular probe, dynamic laser light scattering and rheometer. The results show that it had agood solubility at pH<3.0and pH>6.5. The LSCS could self-aggregate in solution as sphericalmicelles through hydrophobic interaction and the critical micelle concentration (CMC) wasabout0.009mg/mL. As the concentration of LSCS increased, the size of micelles becamelarger. The LSCS could aggregate in water solution through inter-molecular interaction, as aresult, the solution viscosity of LSCS increased significantly with the increasing ofconcentration. When the concentration was up to2.0%(w/w), it presented gel-like behavior.The gel was sensitive to NaCl, and the strength of gel decreased along with the concentrationof NaCl increased.Emulsifying properties were characterized by determining creaming index and particalsize of emulsion, and the efforts of emulsifier types, LSCS concentration, pH andconcentration of NaCl were studied. Results showed that LSCS had better emulsifyingproperties than SCS through hydrophobic interaction. As the concentration of LSCS increased,the emulsifying capacity increased. The stability of emulsion decreased with the pHincreasing from6.5-9, while the addition of NaCl could result breaking of emulsion. LSCSwas used in preparation of skin lotion to investigate its emulsion and thickening performance.The results showed that LSCS could compound with other emulsifier in formula and haveemulsion and thickening effect at the same time. LSCS could also be used as a thickener inskin care system, and variation of the quantity could affect viscosity of the system. |
