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1. Evidence of a liquid–liquid transition in a glass-forming ionic liquid

   https://doi.org/10.1073/pnas.2020878118  

   Harris, Matthew A.; Kinsey, Thomas; Wagle, Durgesh V.; Baker, Gary A.; Sangoro, Joshua (March 2021, Proceedings of the National Academy of Sciences)

   A liquid–liquid transition (LLT) is a transformation from one liquid to another through a first-order transition. The LLT is fundamental to the understanding of the liquid state and has been reported in a few materials such as silicon, phosphorus, triphenyl phosphite, and water. Furthermore, it has been suggested that the unique properties of materials such as water, which is critical for life on the planet, are linked to the existence of the LLT. However, the experimental evidence for the existence of an LLT in many molecular liquids remains controversial, due to the prevalence and high propensity of the materials to crystallize. Here, we show evidence of an LLT in a glass-forming trihexyltetradecylphosphonium borohydride ionic liquid that shows no tendency to crystallize under normal laboratory conditions. We observe a step-like increase in the static dielectric permittivity at the transition. Furthermore, the sizes of nonpolar local domains and ion-coordination numbers deduced from wide-angle X-ray scattering also change abruptly at the LLT. We independently corroborate these changes in local organization using Raman spectroscopy. The experimental access to the evolution of local order and structural dynamics across a liquid–liquid transition opens up unprecedented possibilities to understand the nature of the liquid state. 

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2. Mixed Nanosphere Assemblies at a Liquid–Liquid Interface

   https://doi.org/10.1002/smll.202308560  

   Fink, Zachary; Wu, Xuefei; Kim, Paul Y.; McGlasson, Alex; Abdelsamie, Maged; Emrick, Todd; Sutter‐Fella, Carolin M.; Ashby, Paul D.; Helms, Brett A.; Russell, Thomas P. (November 2023, Small)

   Abstract The in‐plane packing of gold (Au), polystyrene (PS), and silica (SiO₂) spherical nanoparticle (NP) mixtures at a water–oil interface is investigated in situ by UV–vis reflection spectroscopy. All NPs are functionalized with carboxylic acid such that they strongly interact with amine‐functionalized ligands dissolved in an immiscible oil phase at the fluid interface. This interaction markedly increases the binding energy of these nanoparticle surfactants (NPSs). The separation distance between the Au NPSs and Au surface coverage are measured by the maximum plasmonic wavelength (λ_max) and integrated intensities as the assemblies saturate for different concentrations of non‐plasmonic (PS/SiO₂) NPs. As the PS/SiO₂content increases, the time to reach intimate Au NP contact also increases, resulting from their hindered mobility. λ_maxchanges within the first few minutes of adsorption due to weak attractive inter‐NP forces. Additionally, a sharper peak in the reflection spectrum at NP saturation reveals tighter Au NP packing for assemblies with intermediate non‐plasmonic NP content. Grazing incidence small angle X‐ray scattering (GISAXS) and scanning electron microscopy (SEM) measurements confirm a decrease in Au NP domain size for mixtures with larger non‐plasmonic NP content. The results demonstrate a simple means to probe interfacial phase separation behavior using in situ spectroscopy as interfacial structures densify into jammed, phase‐separated NP films. 

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3. Low viscosity liquid bridges: Stretching of liquid bridges immersed in a higher viscosity liquid

   https://doi.org/10.1016/j.jciso.2023.100079  

   Lopez, Ramon; Vaswani, Jovina; Butler, Dylan T.; McCarthy, Joseph; Velankar, Sachin S. (April 2023, JCIS Open)
4. Peeling from a liquid

   https://doi.org/10.1039/D3SM00487B  

   Kumar, Deepak; Zhou, Nuoya; Brau, Fabian; Menon, Narayanan; Davidovitch, Benny (October 2023, Soft Matter)

   We establish the existence of a cusp in the curvature of a solid sheet at its contact with a liquid subphase. 

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5. Polyethylene nano crystalsomes formed at a curved liquid/liquid interface

   https://doi.org/10.1039/c7nr08106e  

   Wang, Wenda; Staub, Mark C.; Zhou, Tian; Smith, Derrick M.; Qi, Hao; Laird, Eric D.; Cheng, Shan; Li, Christopher Y. (January 2018, Nanoscale)

   Crystallization is incommensurate with nanoscale curved space due to the lack of three dimensional translational symmetry of the latter. Herein, we report the formation of single-crystal-like, nanosized polyethylene (PE) capsules using a miniemulsion solution crystallization method. The miniemulsion was formed at elevated temperatures using PE organic solution as the oil phase and sodium dodecyl sulfate as the surfactant. Subsequently, cooling the system stepwisely for controlled crystallization led to the formation of hollow, nanosized PE crystalline capsules, which are named as crystalsomes since they mimic the classical self-assembled structures such as liposome, polymersome and colloidosome. We show that the formation of the nanosized PE crystalsomes is driven by controlled crystallization at the curved liquid/liquid interface of the miniemulson droplet. The morphology, structure and mechanical properties of the PE crystalsomes were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and atomic force spectroscopy. Electron diffraction showed the single-crystal-like nature of the crystalsomes. The incommensurateness between the nanocurved interface and the crystalline packing led to reduced crystallinity and crystallite size of the PE crystalsome, as observed from the X-ray diffraction measurements. Moreover, directly quenching the emulsion below the spinodal line led to the formation of hierarchical porous PE crystalsomes due to the coupling of the PE crystallization and liquid/liquid phase separation. We anticipate that this unique crystalsome represents a new type of nanostructure that might be used as nanodrug carriers and ultrasound contrast agents. 

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