Soft Matter最新文献

Soft colloids are widely used to study glass transition, aging and jamming. A high size polydispersity is typically introduced in these systems to avoid crystal formation. Here, we use binary mixtures of hollow and regular microgels with comparable sizes to inhibit crystallization. The phase behavior of the mixture is probed as a function of the number fraction of hollow microgels and characterized by small-angle X-ray scattering. Molecular dynamic simulations are used to extract the particle–particle pair potential and obtain insight on their deformation. The results suggest that the high deformability of the hollow microgels offers an alternative route to maximize the entropy without crystal formation.

Correction for ‘Flow and clogging of capillary droplets’ by Yuxuan Cheng et al., Soft Matter, 2024, https://doi.org/10.1039/D4SM00752B.

The measurement of ion diffusivity inside nanoporous materials by Pulsed-Field Gradient (PFG) NMR is not an easy task due to enhanced NMR relaxation. Here, we employed multinuclear (¹H, ³¹P, and ⁷Li) NMR spectrometry and diffusometry to probe ion dynamics of a fluorine-free battery electrolyte comprising the [P_4,4,4,4][MEEA] ionic liquid (IL) and LiMEEA salt in a 7 : 3 molar ratio, confined in three different nanoporous SiO₂ glasses with pore diameters of 3.7, 7 and 98 nm. Confinement of the electrolyte leads to NMR resonance line broadening and variation in the ³¹P and ⁷Li NMR chemical shifts. The complicated diffusion decays are explained taking into consideration the complex porous structure of the porous glasses, the presence of pore “necks” and the “partially isolated volumes” containing the liquid, which is in a “slow exchange” regime with the rest of the liquid. The mean apparent diffusivity is controlled by the exchange of ions between the “narrow” and the “large” pores and the boundary separating these pores to measure diffusion coefficients by PFG NMR is in the range of pore sizes of Vycor and Varapor. The temperature-dependent ion diffusivities in the “large” pores deviate from the Arrhenius law and the exchange of diffusing units between the “narrow” and the “large” pores leads to abnormal temperature-dependent diffusion coefficients. Like the bulk, diffusivity of the small Li⁺ is slower than that of the larger organic ions in the confinement, demonstrating the solvation of Li⁺ inside the pores.

Reversible dry adhesion is exploited by lizards and insects in nature, and is of interest to robotics and bio-medicine. In this paper, we use numerical simulation to study how the soft elasticity of liquid crystal elastomers can affect its adhesion and provide a technological opportunity. Liquid crystal elastomers are cross-linked elastomer networks with liquid crystal mesogens incorporated into the main or side chain. Polydomain liquid crystalline (nematic) elastomers exhibit unusual mechanical properties like soft elasticity, where the material deforms at nearly constant stress, due to the reorientation of mesogens. Our study reveals that the soft elasticity of nematic elastomers dramatically affects the interfacial stress distribution at the interface of a nematic elastomer cylinder adhered to a rigid substrate. The stress near the edge of the nematic cylinder under tensile load deviates from the singular behavior predicted for linear elastic materials, and the maximum normal stress reduces dramatically. This suggests that nematic elastomers should display extremely high, but controllable adhesion, consistent with the available experimental observations.

Dip coating a planar substrate with a suspension of particles in a shear-thinning liquid will entrain particles in the liquid film, facilitating filtration and sorting of particles. Experiments were performed for both monodisperse and bidisperse particle suspensions of shear-thinning Xanthan Gum solutions. Particle entrainment occurs when the coating thickness at the stagnation point of the thin film flow is larger than the particle diameter. A model is developed to predict the entrainment criteria using lubrication theory applied to an Ostwald power-law fluid which yields a modified Landau–Levich–Derjaguin (LLD) law governing the coating film thickness that depends upon a properly defined capillary number Ca. The critical withdrawal velocity for particle entrainment depends upon the particle size and fluid rheology through a relationship between Ca and the bond number Bo, which agrees well with our model predictions and prior experimental results of A. Sauret et al. Phys. Rev. Fluids, 2019, 4, 054303 for the limiting case of Newtonian suspensions. Single particle entrainment and particle clustering is observed for monodisperse suspensions, which depends on Ca and the particle volume fraction ϕ. In bidisperse suspensions, particle sorting can occur whereby only the smaller particles are entrained in the film over an active filtration range of Ca and Bo, which also agrees well with our model predictions.

Evaporation of multicomponent drops can induce liquid–liquid phase separation and spatial reconfiguration of phases. Here, we unveil several novel dynamics near the contact line of evaporating multicomponent drops containing polyethylene glycol and dextran. The interplay between background Marangoni flow and self-migration of nucleated microdroplets creates both unstable and stable equilibrium points. This leads to either continuous migration or stepwise advancement of microdroplets, influenced by random coalescence events. Tiny dextran microdroplets nucleating at the contact line can migrate toward the bulk only by growing in size with coalescence events. Our findings offer new insights into the fundamental understanding of evaporating multicomponent drops and factors influencing the spatial segregation of phases in evaporative liquid–liquid phase separation with implications in prebiotic biomolecular reactions to industrial applications.

Due to the sustainability and widespread use of proteins, protein-based materials are extensively utilized in the preparation of Pickering emulsions. However, the relationship between the secondary structure of proteins and their emulsifying ability has not been further investigated. This study used the addition of three different amino acids to influence the interaction between zein chains, which may induce changes in the secondary structure of the prepared zein complex particles. This study demonstrates that the emulsifying properties of proteins, such as dispersibility, zeta potential, three-phase contact angles, interfacial affinity, adsorption rates, and the volume of the stabilized oil phase, are closely related to the β-sheet content of the complex particles, providing a theoretical reference for protein-based stabilizers. Additionally, amino acids, as the blocks of proteins, have high compatibility with proteins, and using amino acids as modifiers aligns with the safety requirements for food processing. In this study, the prepared zein–lysine complex particles have good emulsifying ability, capable of stabilizing a 50 (v/v)% emulsion at a lower concentration (10 mg mL⁻¹), and the prepared emulsion exhibits high-temperature stability and ionic resistance. This characteristic makes the emulsion potentially valuable for application in systems with high salt concentrations and those that may undergo heat treatment.

Hybrid heterostructure materials have received considerable attention due to the integration of each component and abundant functional applications in micromotors, catalysis, photothermal therapy, drug delivery, and bioimaging. However, the preparation of organic/inorganic heterostructure nanoparticles (HSNPs) with high quality still remains a remarkable challenge since thermodynamically metastable structures usually coexist, resulting in a lack of organic scaffolds with extreme uniformity both in shape and size distribution. Here, we prepared polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) core–shell spherical colloids driven by interfacial instability of soft and deformable emulsion droplets. Ultra-low interfacial tension was achieved through the co-adsorption of BCP segments and sodium dodecyl sulfate (SDS) surfactant, which had a strong affinity with the P4VP segment at the interface of the emulsified droplets. The excellent and homogeneous BCP colloids were further utilized as organic scaffolds to selectively grow a functional SiO₂ layer on the surface of the BCP spherical colloids, producing BCP/SiO₂ HSNPs with highly uniform shape and size distribution originating from the PS-b-P4VP scaffolds, thus providing an efficient and general strategy to construct and design organic/inorganic HSNPs with diverse applications.

Supramolecular crystal gels, a subset of molecular gels, are formed through the self-assembly of low molecular weight gelators into interconnecting crystalline fibers, creating a three-dimensional soft solid network. This study focuses on the formation and properties of viologen-based supramolecular crystalline gels. It aims to answer key questions about the tunability of network properties and the origin of these properties through in-depth analyses of the gelation kinetics triggered by thermal quenching. Experimental investigations, including UV-Vis absorption spectroscopy, rheology, microscopy and scattering measurements, contribute to a comprehensive and self-consistent understanding of the system kinetics. We confirm that viologen-based gelators crystallize by forming nanometer radius hollow tubes that assemble into micro to millimetric spherulites. We then show that crystallization follows the Avrami theory and is based on pre-existing nuclei. We also establish that the growth is interface-controlled, leading the hollow tubes to branch into spherulites with fractal structures. Finally, we demonstrate that the gel properties can be tuned depending on the quenching temperature. Lowering the temperature results in the formation of denser and smaller spherulites. In contrast, the gel's elasticity is not significantly affected by the quench temperature, leading us to hypothesize that the densification of spherulites occurs at the expense of connectivity between spherulites.

We have used spin-echo small-angle neutron scattering (SESANS) to probe the hierarchy of structures present in polymer–carbon nanocomposites, with length scales spanning over three orders of magnitude, from 10 nm to 16 μm. The data processing and reduction show a unified approach across two SESANS instruments (TU Delft and Larmor at the ISIS neutron source) and yield consistent data that are able to be modelled using well-established hierarchical models in freely available software such as SasView. Using this approach, we are able to extend the measured length scales by over an order of magnitude compared to traditional scattering methods. This yields information about the structure in the bulk that is inaccessible with conventional scattering techniques (SANS/SAXS) and points to a way for interrogating and investigating polymer nanocomposites routinely across multiple length scales.