Soft Matter最新文献

Ferroelectric nematic liquid crystals (FNLCs) exhibit strong polarization responses, yet accurate evaluation of their dielectric properties without polarization contribution, that is, soft-mode-like dielectric permittivity, remains challenging because fluctuations of spontaneous polarization can lead to an apparent overestimation of permittivity. Here, we investigate the dielectric response of a DIO-based FNLC material under DC electric fields and show that the soft-mode-like contribution can be isolated once the director is reoriented perpendicular to the substrates. At field strengths sufficient to induce this vertical alignment, the peak dielectric relaxation strength becomes independent of cell thickness, consistent with effective suppression of the polarization-related contributions. Using this approach, we determine the DC-field dependence of the transition temperature to the ferroelectric phase and show that the relationship between the transition temperature and the DC field changes across field-induced intermediate phases, consistent with differences in the symmetry of their molecular alignment. In particular, at high fields, the transition from a nematic-like intermediate phase to a ferroelectric phase exhibits characteristics of a second-order phase transition. These results establish a practical route to extract reliable dielectric properties of FNLCs and provide a basis for quantitative physical characterization of this class of materials.

Spherical particles confined to a sphere surface cannot pack densely into a hexagonal lattice without defects. In this study, we use hard particle Monte Carlo simulations to determine the effects of continuously deformable shape anisotropy and underlying crystal lattice preference on inevitable defect structures and their distribution within colloidal assemblies of hard rounded polyhedra confined to a closed sphere surface. We demonstrate that cube particles form a simple square assembly, overcoming lattice/topology incompatibility, and maximize entropy by distributing eight three-fold defects evenly on the sphere. By varying particle shape smoothly from cubes to spheres we reveal how the distribution of defects changes from square antiprismatic to icosahedral symmetry. Congruent studies of rounded tetrahedra reveal additional varieties of characteristic defect patterns within three, four, and six-fold symmetric lattices. This work has promising implications for programmable defect generation to facilitate different vesicle buckling modes using colloidal particle emulsions.

Polymers of intrinsic microporosity (PIMs) offer exceptional gas permeability but remain brittle and susceptible to physical aging, limiting their durability in separation applications. Here, we introduce a reconfigurable microporous polymer network that uniquely integrates permanent PIM microporosity with autonomous, intrinsic self-healing driven by imidazolium-based ionic motifs. Spirobisindane units generate the intrinsic free-volume architecture, while an imidazolium-containing polyamide ionene supplies dynamic ionic and hydrogen-bonding interactions that reorganize under mild activation. Incorporation of imidazolium-based ionic liquids further tunes cohesion, mobility, and densification, enabling the network to relax, re-associate, and retain microporosity without structural collapse. Through a comprehensive multiscale approach combining spectroscopy, scattering, thermal and mechanical characterization with all-atom molecular dynamics and density functional theory calculations, we elucidate how ionic content, as a single control parameter that reshapes free-volume distributions, modulates local coordination environments, and governs relaxation and healing kinetics. At intermediate ionic loadings, the networks achieve rapid, repeatable self-healing while maintaining CO₂ selectivity, demonstrating an optimal balance between segmental mobility and structural integrity. By establishing how hierarchical ionic interactions couple structure, dynamics, and transport in microporous ionene networks, this work provides generalizable design rules for adaptive soft-matter systems that require simultaneous mechanical resilience, reconfigurability, and selective gas transport.

Counter-ion distribution in aqueous ionic surfactant solutions is a complex phenomenon, which is challenging to study experimentally. The degree of counter-ion binding to charged aggregates can significantly impact water activity. In atmospheric aerosols, which often include organic surfactants, such mechanisms may in turn strongly affect cloud droplet formation and earth's radiation balance. Here, we combine ²³Na nuclear magnetic resonance (NMR) relaxation and diffusion experiments with advanced relaxation modelling for determining counter-ion dynamics and distribution in aqueous sodium decanoate solutions. Relaxation modelling of a complex system may require too many parameters to determine. Here, we assume, based our previous ¹H NMR study, that below the critical micelle concentration (CMC), surfactants are monomers or form small clusters (about five decanoate ions), and above the CMC they form small clusters or larger micelles (about 48 decanoate ions). We propose two analytical relaxation models for the system. The number of adjustable parameters is reduced by molecular dynamics simulations. Our analysis indicates that below the CMC, the vast majority (about 97%) of Na⁺ counterions are unbound in the bulk, whereas above the CMC, a significant amount (36-58%) of Na⁺ ions are bound to micelles or clusters, greatly reducing the impact of both Na⁺ ions and surfactant aggregates on water activity. Also, Na⁺ ions associated with micelles undergo fast dynamics with sub nanosecond correlation times.

The modular integration of natural enzymes with synthetic nanozymes provides a promising strategy for creating hybrid catalytic systems with high efficiency and adaptability. However, achieving precise spatial organization and responsive control within a unified scaffold remains challenging. Herein, we report a Pickering emulsion-guided approach to fabricate responsive microgel-laden microcapsules, termed microgelsomes (MGC). Using oil-water emulsion droplets as templates, catalytic Fe₃O₄ nanoparticle-loaded poly(N-isopropylacrylamide-co-serine) microgels (Fe-PNSER) were assembled at the interface to form microcapsules that act as catalytic reactors. By incorporating enzymes in the aqueous core and Fe₃O₄ nanoparticles within the microgel membrane, self-contained chemo-enzymatic cascade reactors with tightly coupled reaction pathways were constructed. Using a glucose oxidase (GOx)/Fe-PNSER cascade as a model reaction, these multicompartment reactors showed roughly two-fold higher efficiency than homogeneous systems or simple mixtures of the same components, highlighting the advantage of spatially organized hybrid catalysis. The system also offers tunable properties, robustness, and compatibility for integrating diverse catalytic functions. This work provides a versatile and scalable platform for designing next-generation hybrid reactors with combined structural precision and functional synergy.

We analyzed the effect of charge density (CD) on the phase behavior, viscoelasticity, and underwater adhesion of complex coacervates formed from high-molecular-weight, semi-flexible, bio-sourced polyelectrolytes. For this, hyaluronic acid (HA) was complexed with chitosan (CHI) of different degrees of deacetylation (DD) at pH 5.0. It was found that increasing CHI deacetylation enhanced macroion pairing, expanding the two-phase region of the phase diagram. Time-salt superposition (TSS) was successfully applied, allowing us to rescale the linear viscoelastic response of all the HA-CHI series onto individual master curves, indicating that the relaxation dynamics of all series are controlled by macroion pairing. The TSS curves were further collapsed onto a universal master curve via a so-called time-salt-charge density superposition (TSCDS). This first report of TSCDS for entangled complex coacervates revealed that the salt sensitivity of the dynamics depends on the charge density, which is in contrast with reports on flexible polyelectrolytes. It is proposed that this difference is due to the interplay between the persistence length of the semi-flexible polyelectrolytes and kinetic trapping in these entangled systems. The underwater adhesion strength (σ_max) of HA-CHI reached 74 kPa at 0.2 M NaCl. Replacing CHI's acetyl moiety with a less polar butyryl group (but-CHI) at a given DD had a slight effect on the composition and viscoelastic properties. However, HA-but-CHI had the highest underwater adhesion near physiological salinity (σ_max of 110 kPa and an adhesion energy of 18 J m^-2), placing it among the most high-performing coacervate-based underwater adhesives without an external trigger.

Compound droplets of complex fluids (such as polymeric liquids) are becoming increasingly prominent for their applications in targeted drug delivery, cell and particle encapsulation, and many other micro- and millifluidic processes. Despite this, the morphological behaviors of such drops are yet to be properly addressed even in simple canonical flows. The main challenge in this regard perhaps originates from the complex and non-linear constitutive relation of the constituent fluids. To address this, here, we analyze the flow field and the deformations of a compound viscoealstic drop, subject to uniaxial extensional flows. All three phases are considered to obey the Giesekus constitutive model, known for its ability to accurately capture the rheological properties of many polymeric liquids. We derive asymptotic solutions for the limiting case of small deformation and weak viscoelasticity, and subsequently validate them against full numerical simulations based on the ternary phase field method. The results, derived mainly from the asymptotic analysis, demonstrate that the elongational elastic stresses help reduce the deformations in both the shell and the core, and this is facilitated by the shear-thinning nature and the finite extensibility of the Giesekus model. We also show that depending on the extent of viscoelasticity of the outermost phase and the core size, the shape of the shell may change from prolate to oblate and vice versa for the core. The viscoelasticity of the core on the other hand has relatively little influence on the deformation of the shell, although it is found to significantly impact the core's evolution.

While the autonomous assembly of hard nanoparticles with different shapes has been studied extensively both in experiments and simulations, little is known about systems where particle shape can be dynamically altered. DNA origami nanostructures offer an alternative route to synthesize nanoparticles that can change their shape on demand. Motivated by recent experiments, here we study the structure and dynamics of suspensions of hard squares in response to an elongation into a rectangle. Performing dynamic hard-particle Monte Carlo simulations at constant volume and employing two protocols, we numerically analyze the collective diffusion and ordering during the shape change and the subsequent relaxation towards the new equilibrium state. We find that the cascading protocol, which mimics experimentally realized DNA origami, can become dynamically arrested due to the increase in effective packing fraction.

Mechanical oscillations play fundamental roles in cellular processes such as motility, signalling, and structural regulation; however, the mechanisms by which artificial cytoskeletal networks can be engineered to reproduce such autonomous oscillatory behaviours remain poorly understood. In this study, we demonstrate that a chemically polyethylene glycol-crosslinked filamentous actin hydrogel exhibits autonomous, long-lasting, and synchronised mechanical oscillations during self-organised polymerisation. These oscillations arise from chemo-mechanical responses coupled with the treadmilling polymerisation-depolymerisation equilibrium of filamentous actin. We propose that the rigid and highly hierarchical structure of the chemically crosslinked network plays an important role in the emergence of such autonomous mechanical oscillations. Our results reveal how hierarchical crosslinking and chemo-mechanical coupling drive sustained oscillations in active polymer networks, providing new insight into the fundamental mechanisms underlying autonomous dynamics in soft materials.

We use a combination of experiments, mathematical modelling, and parameter estimation to better understand how agar density affects colony biofilm growth of the yeast species Saccharomyces cerevisiae. We obtained 15 total experimental replicates on rectangular plates filled with 0.6%, 0.8%, 1.2%, and 2.0% agar. In the experiments, we measured the horizontal expansion over time, the number of living cells, and the colony biofilm aspect ratio. These measurements quantify the colony biofilm size, composition, and shape, respectively. We modelled colony biofilm expansion using a thin-film extensional-flow mathematical model. By fitting five unknown model parameters to mean experimental data, we show that nutrient uptake decreases and biofilm-substratum adhesion strength increases with an increase in agar density. Sensitivity analysis, fitting to individual replicates, and synthetic-data analysis confirmed that increased biofilm-substratum adhesion is the most consistent effect of increased agar density. This finding aligns with similar results reported for bacteria, and suggests that substratum properties are important for yeast colony biofilm growth.