Synthesis and characterization of a novel amphiphilic chitosan–polylactide graft copolymer

Water soluble chitosan (CS) derivatives containing polylactide unit were synthesized by reacting dl-lactide (DLLA) with chitosan in dimethyl sulfoxide solution in the presence of triethylamine. The chemical structure and physical properties of chitosan derivatives were characterized by FTIR, 1HNMR, TGA and XRD. Formation and characteristics of polymeric micelles of graft copolymers were studied by fluorescence spectroscopy and dynamic light scattering (DLS) method. The critical micelles concentration (cmc) of polymeric amphiphiles was determined by measuring the fluorescence intensity of pyrene as a fluorescent probe. The cmc value of DLLA/CS (11:1) (dl-lactide/aminoglucoside units molar ratio=11:1) in water was 6.49×10−2 mg/ml. The size of micelles and their size distribution in water were measured by DLS. Mean diameter of the polymeric amphiphiles micelles of DLLA/CS (11:1) in water was 154 nm with an unimodal size distribution (polydispersity=μ/Γ2=0.03). The spherical micelles were observed by transmission electron microscopy (TEM).