Achieving high viscoelasticity in additive-free anionic surfactant systems remains a significant challenge. Herein, taking the natural product resveratrol as the starting material, a series of resveratrol-based star-type trimeric anionic surfactants...
Classical contact mechanics is widely used to describe mechanical coupling in nanoparticle assemblies, yet its validity at the nanoscale remains experimentally unresolved. Here, we investigate size-dependent collective vibrational dynamics in...
Conventional emulsion lubricants suffer from issues such as oil film rupture under high loads, poor lubrication stability and insufficient load-carrying capacity. To address these issues, this study developed an acrylic polymer emulsion (PAS) with a simple composition and KH570-modified hydroxylated boron nitride nanosheets (KH570-OH-BNNS), which were used to prepare a nanocomposite emulsion lubricant via in situ polymerisation. The resulting emulsion lubricant exhibits excellent stability, lubricity and load-carrying capacity. Under a test load of 294 N, a minimum coefficient of friction of 0.047 was achieved, representing a reduction of 85.6% compared with the base lubricant. The wear rate was as low as 1.03 × 10-9 mm3 N-1 m-1, whilst the maximum anti-seize load (PB) reached 1579 N. The lubrication mechanism indicates a synergistic effect between the polymer matrix and the modified boron nitride nanosheets at the friction interface, forming a dense organic-inorganic lubricating film that effectively prevents direct contact between steel surfaces, thereby exhibiting excellent tribological performance. This study provides a new strategy for the design of high-performance water-based emulsified lubricants and expands their potential applications in the field of lubrication.
Perceiving the surrounding environment via hydrodynamic signals is a critical survival skill for numerous aquatic organisms and represents a promising technology for intelligent robotic platforms. This study investigates the wall-detection...
Solutions of partially depolymerized xanthan gum which form cholesteric lyotropic liquid crystal (LLC) phases, can be used to produce structurally colored, non-brittle photonic films. A key factor which determines the photonic properties of the dried xanthan films is the helical pitch p in the solid cholesteric structure retained from the liquid crystal phase, which enables the films to selectively reflect visible light. However, detailed experiments and a sophisticated theoretical model for unraveling the evolution of helical pitch over a broad concentration range in LLC systems containing semiflexible building blocks have remained elusive. In this work, we systematically study the temperature and concentration dependence of the helical pitch in aqueous solutions of ultrasonically treated xanthan gum over an extended concentration range up to 30 wt%. This investigation reveals that while the inverse pitch, i.e. the helical twist, decreases linearly with temperature, it grows much more dramatically with concentration. Current theories cannot explain such strong non-linear concentration dependence of the inverse pitch at high concentration. Therefore, we propose a new molecular statistical model based on the so-called generalized van der Waals theory (GVWT) of the nematic phase, taking into account the concentration dependent steric intermolecular correlations as well as the effective attraction interaction. This model successfully interprets the divergence of the inverse pitch at high concentrations and estimates reasonable minimum achievable pitch values in the dried films as observed for the xanthan samples. These findings reinforce our understanding of chiral interactions in semiflexible LLCs, more deeply bridging the cholesteric ordering and structural coloration in solid films.
Understanding the dissociation vs. varied salt conditions in weakly charged polymers is critical to develop innovative charged polymers for sustainability.
Further investigation was carried out into the mechanism underlying the changes in electric resistance in an aqueous solution of poly(sodium acrylate) induced by a vigorous flow, as we had previously observed. The change in resistance increased with concentration and showed a broad peak at a NaPAA concentration of approximately 2 × 10-3 wt%, which was close to the entanglement concentration (1.2 × 10-3 wt%). The change in resistance of the NaPAA solution increased with increasing frequency and tended to reach a plateau above approximately 3 × 103 Hz. The absolute value of the change in resistance due to the flow could be quantitatively explained by the decrease in the polymer concentration.
Correction for 'Droplet breakup against an isolated obstacle' by David J. Meer et al., Soft Matter, 2026, 22, 2809-2822, https://doi.org/10.1039/d5sm01266j.
This research addresses the challenge of controlling complex director fields in confined chiral liquid crystal (CLC) geometries. CLC droplets were inkjet-printed onto high-resolution photoalignment patterns to study the competition among chiral pitch, geometric confinement, and surface-alignment periodicity. Polarized microscopy analysis and conceptual 3D modeling reveal that surface photoalignment dictates the droplet structure, steering the director field independently of the curved droplet's profile. Findings show that at small periods Λ, surface anchoring suppresses domain curvature in favour of a well-defined 1D director lattice. This transition confirms that photoalignment can either enforce directional orientation or allow curvilinear fields depending on the confinement.
Conductive hydrogels have great potential as sensing materials for wearable flexible electronics; however, their practical applications are often limited by low mechanical strength, poor adhesion, and low self-healing efficiency. To meet the requirements of flexible wearable sensors, in this study we introduced zinc trifluoromethanesulfonate (Zn(CF3SO3)2) into the network structure of polyacrylic acid (PAA) and prepared a polyacrylic acid/zinc trifluoromethanesulfonate (PAA/Zn(CF3SO3)2) conductive hydrogel via free radical polymerization. The addition of Zn(CF3SO3)2 not only improves the ionic conductivity but also enhances the crosslinking density through metal coordination. The PAA/Zn(CF3SO3)2(6 wt%) conductive hydrogel exhibits excellent mechanical properties, with a tensile strength of 1.628 MPa, an elongation at break of 670%, and a high electrical conductivity of 1.212 S m-1. Furthermore, this hydrogel exhibits good moisture retention, anti-swelling, self-healing, and adhesive properties. Importantly, the wearable sensor based on the PAA/Zn(CF3SO3)2(6 wt%) hydrogel exhibits a wide detection range, fast response time, negligible hysteresis, and high sensitivity (GF = 4.56 at 400-600% strain), enabling accurate capture of large-scale human motions as well as movements such as mouth opening and swallowing. This study demonstrates a multifunctional, high-performance conductive hydrogel, showing promise for applications in wearable health monitoring.
Adjusting the formulations of aqueous solutions to maximize their power to clean oil soils from solid substrates, often called detergency, is mostly based on empirical knowledge. Here, we quantitatively describe the removal of a single oil droplet attached to a solid wall under the action of a flow of surfactant solutions. To do so, we design a microfluidic set-up allowing control of the flow and monitoring of the droplet volume, shape, contact area and its detachment. We work with surfactant solutions whose varied composition allows us to span a wide range of both oil solubility and interfacial tension: the system forms microemulsions. Two detergency regimes are identified and described. (i) At large flow rates, the viscous shear forces the droplet to detach which is well accounted for by a single-valued capillary number. As a result, the detachment threshold depends on the antagonistic effects of the detergent composition on the wetting of oil on the solid and the interfacial tension that we describe. (ii) Below the threshold for detachment, the oil from the droplet is solubilized into the detergent according to the advection-diffusion model for transport. This allows us to predict the optimum composition. In both cases we release quantitative predictions, provided that independent characterization studies, using conventional methods, of the oil solubility, micelle size and concentration, interfacial tension and wetting angles are available.
Peptide-based supramolecular assemblies provide experimentally accessible model systems for probing structure-property relationships in soft molecular materials. Here, three short β-sheet-forming peptides with graded histidine substitution were designed as minimal supramolecular networks to systematically examine how sequence-level variation regulates supramolecular organization, viscoelastic response, and pH-modulated molecular transport in aqueous environments. All peptides spontaneously assembled into β-sheet-rich nanofibrous networks, as confirmed by spectroscopic and microscopic characterization, and exhibited stable viscoelastic behavior with pronounced reversible self-recovery. Using doxorubicin as a representative small-molecule probe, the assemblies displayed distinct pH-dependent transport regimes, and kinetic analysis based on the Korsmeyer-Peppas model revealed sequence- and pH-dependent differences in release behavior. Rather than focusing on detailed molecular-level mechanisms, this work emphasizes experimentally accessible correlations between supramolecular network structure, mechanical response, and transport behavior. These results highlight histidine-substituted β-sheet peptide assemblies as adaptable soft-matter model systems for investigating pH-regulated transport phenomena in supramolecular networks.
Silica gels are colloidal hydrogels that can be used in drug delivery techniques, and the introduction of proteins into the system would be of interest in cases where the protein is the element to be delivered. In this study repulsive colloids (silica particle) are mixed with ionic species to form a fractal gel. We then study the impact of adding a protein (bovine serum albumin (BSA)), whose overall charge is the same sign as silica, on the structural and mechanical properties of the gel. Thanks to SAXS and rheology measurements, we can deduce some micro and macro parameters such as, the interaction potential between beads, the gelation time, the elastic modulus and the critical strain of the gel and their variation with the volume fraction in BSA. The protein allows to form gels with very low ionic strength compared to the case without proteins; BSA acts as a binding agent between the silica particles. Thanks to a power-law model, hypotheses are proposed about the gel structure, to make a link between the structure and the mechanical properties.
The material properties of connective tissues are often considered to be dominated by the extracellular matrix. However, cells within tissues contribute significantly to the mechanics, particularly when considering volume-changing deformations such as axial compression. Recent studies have considered the compression response of model tissues at long times, where the role of the interstitial fluid is negligible. Here, we experimentally study the interplay of matrix, cell and fluid mechanics in the short time response of model tissues based on fibrous networks with embedded microgel inclusions as passive cell-like mimics. By simultaneously applying compression at a fixed strain rate while measuring the shear modulus via small strain shear oscillations, we show that at long times fibrous networks transition from compression-softening behaviour to compression-stiffening behaviour upon incorporation of microgel particles. At short times, however, we show that fluid pressure build-up leads to significant compression-stiffening, regardless of the inclusion of microgels. Our findings demonstrate that the role of fluid pressurisation is key to understanding the response of tissues to deformations on timescales on the order of a few seconds, common in many tissues subject to physiological deformations.
The ethylene oxide (EO)/propylene oxide (PO) triblock copolymers (EO)m-(PO)n-(EO)m, also known as poloxamers, self-assemble in aqueous solution due to the differences in hydrophobicity between EO and PO. Both the overall length of the blocks and their relative lengths in the copolymer impact self-assembly. Even though poloxamers lack charge, they respond to the presence of salts, including ionic liquids (ILs). Here, the response of poloxamer 188 to 1-alkyl-3-methylimidazolium chlorides having long and short alkyl chains was studied by small-angle neutron scattering. The dilute state of both the polymer and ILs was studied, with the IL concentrations being below published critical micelle concentrations. The goal was to probe initial stages of self-assembly. The results demonstrate a clear interaction between the long chain imidazolium chloride and the poloxamer that is surfactant-like, which is not observed for the short alkyl chain salt.
Molecular dynamics simulations were performed to investigate the structural evolution and frictional behaviors of breaking polymer brushes subjected to shear imposed by a moving wall with systematic comparisons to non-breaking systems. Our results show that the structural and dynamical properties of breakable brushes are strongly coupled with the shear velocity. At low wall velocities, bond cleavage is rare, and the two systems exhibit nearly identical structural and frictional responses. With increasing wall velocity, brush chains become progressively stretched and oriented along the shear direction, leading to bond rupture. Bonds with the highest degree of shear-induced orientation are more susceptible to breaking, while the location of maximum orientation shifts with wall velocity, i.e., the polydispersity of free and brush chains are altered by the velocity. When the wall velocity exceeds a critical value, a large number of free chains accumulate near the moving wall and form a mobile interfacial lubricating layer, resulting in a pronounced self-lubrication effect. In this high-velocity regime, the friction coefficient decreases by approximately one order of magnitude relative to the corresponding non-breaking system. Moreover, this critical velocity decreases with increasing chain length. Further analysis reveals that, compared with the contact number, which is conventionally used to estimate the strength of friction, chain orientation maintains a robust linear relation with the friction coefficient over a much broader shear range, therefore serves as a more reliable descriptor for the interfacial frictional response. This study elucidates the molecular mechanism of bond-breaking-induced self-lubrication in polymer brushes and provides physical insights for the design of polymer-brush interfaces with tunable frictional properties.
The liquid crystalline ferroelectric nematic (NF) phase is well known for its distinctive physical and electrical properties, namely the bulk polarity. It is therefore important to consider whether the nematic bulk properties are affected by very highly polar molecules and underlying polar phases. In this paper, we present a detailed temperature-dependence of the splay (K11) and bend (K33) elastic constants, and the Fréedericksz threshold voltage for a positive dielectric anisotropy LC mixture exhibiting both non-polar (N) and polar (NF) nematic phases, and include theoretical discussions. Such properties are compared to those of two conventional nematic liquid crystals (NLCs). In the NF LC mixture, we show a marked reduction in the splay elastic constant (1.8-0.5 pN) and the threshold voltage (150-35 mV), across the nematic phase, at temperatures much lower than the nematic to isotropic transition. The values for K11 and Vth linearly extrapolate to 0 pN and 0 V respectively, at the nematic to the intermediate nematic (NX) phase transition. Such reduction in the splay elastic constant, which is a deviation from conventional nematic behaviour, is attributed to flexoelectric coupling becoming significant at these temperatures. Corrections with temperature dependent flexoelectric coupling for the elastic constants, dielectric permittivity, and Fréedericksz threshold voltage, are discussed in detail.
The equilibrium shear modulus of some swollen polymer networks decreases with increasing temperature, even when the corresponding dry network shows the classical positive temperature coefficient of entropic elasticity. This sign reversal cannot be explained by the conventional Frenkel-Flory-Rehner framework, in which the mixing free energy is assumed independent of deformation. We show that allowing the Flory-Huggins parameter χ to depend on isochoric strain invariants, a thermodynamically general but previously unexplored possibility, resolves this inconsistency. Within continuum thermodynamics, this yields, to leading order under commonly encountered conditions, an affine modulus-temperature relation, Geq = θ(X - Y) +ΘY, which separates the dry-network contribution X from a solvent-mediated contribution Y. The resulting structure defines an experimental strategy: measure dry and swollen networks over temperature and concentration, then test the consistency of Y inferred from slope and intercept, or directly when Θ is known independently. We apply this framework to poly(n-butyl acrylate) swollen in butyl benzoate and poly(ethylene glycol) swollen in dimethylformamide, obtaining Y < 0 and Y > 0, respectively. For the latter system, the fitted Θ agrees with the known crystallization temperature of poly(ethylene glycol) in dimethylformamide. The present work establishes a thermodynamic framework and validation strategy for solvent-deformation coupling in swollen networks, while leaving molecular identification to future study.
A strategy for the fabrication of porous polymeric micro-/nanomaterials via reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) has been proposed. The process is regulated by tuning the stepwise addition strategy of the macromolecular chain transfer agent (macro-CTA). A systematic study was carried out on three types of polymerization-induced self-assembly (PISA) systems, including redox-initiated and photo-initiated aqueous emulsion polymerization of glycidyl methacrylate (GlyMA), as well as thermally initiated dispersion polymerization of styrene (St) in methanol. All systems were mediated by the same poly(ethylene glycol) methacrylate (PPEGMA) macro-CTA. Experimental results show that all three polymerization-induced self-assembly systems can successfully prepare porous polymer micro-/nanomaterials with regular morphology, tunable pore size, and abundant pores, namely PPEGMA9.1-b-PGlyMAn and PPEGMA9.1-b-PSn. It should be noted that the redox and thermal systems are comprehensively characterized by kinetic and GPC tests, while the photoinitiated system only acts as a supporting demonstration based on TEM images in the supplementary information. Moreover, the process conditions for achieving porous morphologies were explored by adjusting the molar ratio of the macro-CTA added in batches, the time intervals between additions, and the monomer concentration.
Most coarse-grained models of the nanoscale self-assembly process employ rigid building blocks that do not exhibit shape adaptation, limiting our understanding of the role of elasticity in altering self-assembly pathways. We study how bending rigidity of nanoscale building blocks affects their self-assembly using microsecond-long Langevin dynamics simulations of a coarse-grained model of deformable building blocks. Our model is inspired by the protein subunits, also known as capsomers, of a typical small icosahedral virus system. Transitions in assembly products from dispersed capsomers to symmetric cages to malformed aggregates are observed with increasing bending modulus of the capsomer. Simulations find a mechanical "goldilocks zone" in the space of capsomer bending modulus and capsomer-capsomer steric attraction for successful protein cage formation, where capsomers are sufficiently rigid to suppress strong shape fluctuations and promote capsid assembly nucleation, and also sufficiently soft to correct errors during the capsid growth pathway. The pronounced effects of changing capsomer bending rigidity on the steady-state assembly products are linked to the changes in the assembly kinetics, and explained by the variations in the angular fluctuations characterizing the capsomer and associated "shape entropy" costs. We apply the deformable capsomer model to probe the encapsulation of charged nanoparticles and show that encapsulation behavior depends on capsomer elasticity. Our results highlight how block elasticity can guide nanoscale assembly and provide a computational framework for designing deformable particles and reconfigurable materials.
