Characterization of the Micelle Formed by a Hydrophobically Modified Pullulan in Aqueous Solution: Size Exclusion Chromatography

Size exclusion chromatography equipped with a multi-angle, light-scattering online detector (SEC-MALS) measurements were carried out on a hydrophobically modified pullulan (PUL-OSA) with degrees of substitution (DS) of 0.14, 0.2, and 0.3 in 0.01 M aqueous NaCl to obtain the degree of polymerization (N-0) dependence of the radius of gyration (< S-2 >(1/2)) for PUL-OSA in the aqueous NaCl. The result was consistent with the loose flower necklace model proposed in a previous study, and the increase in the chain size with introducing OSA groups was explained by the backbone stiffness of the loose flower necklace formed by PUL-OSA. For PUL-OSA samples with DS = 0.2 and 0.3, < S-2 >(1/2) obtained by SEC-MALS in a high N-0 region deviated downward from < S-2 >(1/2) expected by the loose flower necklace model. This deviation came from a tiny amount of the aggregating component of PUL-OSA, taking a branched architecture composed of loose flower necklaces. Although the aggregating component of PUL-OSA was also detected by previous small angle X-ray scattering measurements, its conformation was revealed in this study by SEC-MALS.

Automated summary

Size exclusion chromatography equipped with a multi-angle, light-scattering online detector (SEC-MALS) was used to study the influence of degrees of substitution (DS) on the radius of gyration for hydrophobically modified pullulan (PUL-OSA) in aqueous NaCl solution. Results showed that the introduction of OSA groups led to an increase in chain size, consistent with the loose flower necklace model. However, samples with higher DS values exhibited deviations from the expected values due to the presence of aggregating components with a branched architecture composed of loose flower necklaces.