Cryogenic Electron Microscopy Study of Nanoemulsion Formation from Microemulsions

We examine a process of preparing oil-in-water nanoemulsions by quenching (diluting and cooling) precursor microemulsions made with nonionic surfactants and a cosurfactant. The precursor microemulsion structure is varied by changing the concentration of the cosurfactant. Water-continuous microemulsions produce initial nanoemulsion structures that are small and simple, mostly unilamellar vesicles, but microemulsions that are not water-continuous produce initial nanoemulsion structures that are larger and multilamellar. Examination of these structures by cryo-electron microscopy supports the hypothesis that they are initially vesicular structures formed via lamellar intermediate structures, and that if the lamellar structures are too well ordered they fail to produce small simple structures

Almost Fooled Again: New Insights into Cesium Dodecyl Sulfate Micelle Structures

Replacing sodium with cesium as the counterion for dodecyl sulfate in aqueous solution results in stronger complexation and charge shielding, which should lead to larger micelles and ultimately to a cylindrical structure (cf. spheres for sodium dodecyl sulfate), but small angle X-ray scattering (SAXS) and small angle neutron scattering patterns previously have been interpreted with ellipsoidal micelle models. We directly image CsDS micelles via cryo-transmission electron microscopy and report large core–shell spherical micelles at low concentrations (≤2 wt %) and cylindrical micelles at higher concentrations (5.0 and 8.1 wt %). These structures are shown to be consistent with SAXS patterns modeled using established form factors. These findings highlight the importance of combining real and reciprocal space imaging techniques in the characterization of self-assembled soft materials

Design and Characterization of a PVLA-PEG-PVLA Thermosensitive and Biodegradable Hydrogel

A set of poly­(δ-valerolactone-<i>co</i>-d,l-lactide)-<i>b</i>-poly­(ethylene glycol)-<i>b</i>-poly­(δ-valerolactone-<i>co</i>-d,l-lactide) (PVLA-PEG-PVLA) triblock copolymers was synthesized and the solution properties were characterized using rheology, cryo-TEM, cryo-SEM, SANS, and degradation studies. This polymer self-assembles into a low viscosity fluid with flowerlike spherical micelles in water at room temperature and transforms into a wormlike morphology upon heating, accompanied by gelation. At even higher temperatures syneresis is observed. At physiological temperature (37 °C) the hydrogel’s average pore size is around 600 nm. The PVLA-PEG-PVLA gel degrades in about 45 days in cell media, making this unique hydrogel a promising candidate for biomedical applications

Tunable Oleo-Furan Surfactants by Acylation of Renewable Furans

An important advance in fluid surface control was the amphiphilic surfactant composed of coupled molecular structures (i.e., hydrophilic and hydrophobic) to reduce surface tension between two distinct fluid phases. However, implementation of simple surfactants has been hindered by the broad range of applications in water containing alkaline earth metals (i.e., hard water), which disrupt surfactant function and require extensive use of undesirable and expensive chelating additives. Here we show that sugar-derived furans can be linked with triglyceride-derived fatty acid chains via Friedel–Crafts acylation within single layer (SPP) zeolite catalysts. These alkylfuran surfactants independently suppress the effects of hard water while simultaneously permitting broad tunability of size, structure, and function, which can be optimized for superior capability for forming micelles and solubilizing in water