0428同步年報-2021-全

036 ACTIVITY REPORT 2021 shape of micelles is either elliptic or short-cylindrical, which can move freely; thus the viscosity is small. As S 0 increases, the reverse micelles grow into long, flexible cylinders that entangle one another to enhance greatly the viscosity and even lead to gelation. Above a critical S 0 , the length of micelles decreases and the viscosity decreases accordingly. Fourier-transform infrared spectroscopy (FT-IR) techniques were utilized to investigate the interactions between inorganic salts and the functional groups on lecithin ( Fig. 2(c) ). The data show that the inorganic salts initially bind to the lecithin headgroup and hold lecithin more tightly through strong electrostatic interactions. The lecithin molecules are thus more straightened and more densely packed, causing a CPP change that transforms the nearly spherical micelles into cylindrical ones. Once the headgroups are saturatedly bonded with the salts, the excess salts move to the ester linkages on lecithin where they work as a spacer that separates the tails, which in turn disrupts the regular packing of the tails so that the tail area expands accordingly. The long cylindrical micelles thus break into short ones and the viscosity sharply decreases ( Fig. 3 ). The results highlight the importance of the location of the inorganic salts on lecithin in the self-assembly of lecithin reverse micelles. In summary, through a systematic study of the lecithin reverse worms induced by inorganic salts, the rheological properties, the self-assembled structures and the interactions between lecithin and salts were well correlated. This work manifests the crucial role of the binding site of the salts in the micellar structure and rheological behaviours of lecithin reverse micelles. Although this study focused on the reverse system, the findings in this work might be significant also for aqueous systems in which the interaction between inorganic salts and lipid bilayers is critical in physiological functions. (Reported by Shih-Huang Tung, National Taiwan University) This report features the work of Shih-Huang Tung and his collaborators published in J. Mol. Liq. 329 , 115543 (2021). TLS 23A1 Small/Wide Angle X-ray Scattering ANSTO BILBY – Small-angle Neutron Scattering • SAXS, WAXS • Soft Matter, Nanomaterials, Alloy References 1. S.-T. Lin, C.-S. Lin, Y.-Y. Chang, A. E. Whitten, A. Sokolova, C.-M. Wu, V. A. Ivanov, A. R. Khokhlov, S.-H. Tung, Lang- muir 32 , 12166 (2016). 2. C.-Y. Lin, S.-H. Tung, J. Mol. Liq. 329 , 115543 (2021). Fig. 3 : Schematic of reverse micellar structures formed by lecithin with inorganic salts. The binding sites of salts on lecithin affect the effective molecular geometry and thus cause altered micellar structures. [Reproduced from Ref. 2]