Measuring the spheroidal shapes of soft molecular aggregates using partial molar volume and DLS measurements: Triton X-100 micelles and reverse micelles

A microscopic volumetric method of measuring partial molar volume was employed in conjunction with dynamic light scattering measurements to identify the shapes of Triton X-100 micelles in water and reverse micelles in cyclohexane. It was found that the shape of Triton X-100 micelles in water depends strongly on the amount of water absorbed into the micelle. Water molecules in this context serve the purpose of hydrating the polyethylene oxide (PEO) moieties while also penetrating the PEO region. To date, measurements have yielded two distinct values for Xw: 42 and 90 water molecules. the importance of the dissimilar Xw values lies in their ability to shed light on the behavior of Triton X-100 in the presence of water, which has implications for a wide range of scientific and practical applications, from materials science to pharmaceuticals and biotechnology. We observed spheroidal forms of micelles for 42 water molecules per surfactant with a Triton X-100 up to a concentration of 15.00 %. However, with 90 water molecules per surfactant, we saw nearly spherical micelles up to a 5.00 % Triton X-100 concentration; at this concentration, we saw prolate and oblate spheroids with an aspect ratio in the 0.5-2.0 range. Yet, we were unable to detect a spheroidal shape for Triton X-100 reverse micelles. Dynamic Light Scattering was used to identify the size of the particles in the micelle and reverse micelle solutions at 25.0 OC and 30.0 OC respectively. The analysis of the radius of Brenner's theory from the PMV measurements and the radius of DLS measurements was not even close. Brenner's theory aids in understanding how oddly shaped particles, like spheroids, move in liquids. It helps validate DLS results and provides a fuller picture of their behavior, crucial for non-spherical particles in solutions. The study of Brenner's theory's radius based on PMV observations and that of the DLS data were not even near. This includes that non-spherical micelles were present in the reverse micellar solution