Micellar structure of decenyl succinic anhydride modified pullulan with degree of substitution dependence in aqueous...

A broad distribution pullulan (PUL) sample was hydrophobically modified by a relative longer decenyl succinic anhydride (DCSA) side chains with seven different degree of substitution (DS) to obtain the PUL-DCSA. The micellar structure of PUL-DCSA with DS dependence was investigated by pyrene-probe fluorescence and small-angle X-ray scattering (SAXS) in 0.05 M aqueous NaCl. While PUL-DCSA with DS > 0.26, both the SAXS and fluorescence results can be explained by the flower necklace model, when DS < 0.26, PUL-DCSA forms the loose flower necklace model. Moreover, the micellar structure of PUL-DCSA characterized by SAXS and fluorescence was different from that of the PUL-bearing shorter alkyl (octenyl or nonenyl) chains. The smaller chain stiffness q_FN and larger number of monomer (glucose residues) per unit flower micelle N_0u of PUL-DCSA, mainly due to the difference in the different hydrophobic alkyl side chains. This research will provide a theoretical guidance for designing biomedical materials with appropriate scale and characteristic functions in drug delivery system.