Soft Matter最新文献

Topologically nontrivial adiabatic loops of the orientation of a homogeneous external magnetic field drive the walking of paramagnetic colloidal bipeds above a deformed quasi-periodic magnetic square pattern. Depending on the topological properties of the loop we can simultaneously control the walking directions of colloidal bipeds as a function of their size and as a function of the size of a deformed unit cell of the pattern. The bipeds walk performing steps with their two feet alternatingly grounding one foot and lifting the other. The step width of the bipeds is given by a set of winding numbers (w_x, w_y) ∈ ² - a set of topological invariants - that can only change by integers as we continuously increase the length of the bipeds. We experimentally use this discrete size dependence for the robust sorting of bipeds according to their length.

This study explores the encapsulation of magnetic and non-magnetic hydrogels within a liquid medium using the liquid-liquid encapsulation technique. The encapsulation process involves the suspension of hydrogels in laser oil, followed by the generation of compound core droplets, which are then wrapped by an interfacial layer of canola oil floating on a water bath. This method produces magneto-responsive compound encapsulated cargos with potential applications in diverse fields such as drug delivery, tissue engineering, and soft robotics. The magnetic properties of these encapsulated cargos are exploited for magnet-assisted release and underwater manipulation, demonstrating enhanced stability, controlled release, and adaptability. This research opens new avenues for the application of magnetic hydrogels in dynamic and responsive systems.

We utilize the generalized entropy theory (GET) of glass formation to address one of the most singular and least understood properties of polymer glass-forming liquids in comparison to atomic and small molecule liquids-the often relatively high fragility of the polymer dynamics on a segmental scale, m_s. Based on this highly predictive framework of both the thermodynamics and segmental dynamics in terms of molecular structure, polymer backbone and side-group rigidities, and intermolecular interaction strength, we first analyze the relation between m_s and the ratio, , where S_c is the configurational entropy density of the polymer fluid, equals S_c at the onset temperature T_A for non-Arrhenius relaxation, and T_g is the glass transition temperature at which the structural relaxation time τ_α equals 100 s. While the reduced activation energy estimated from an Arrhenius plot (i.e., differential activation energy) normalized by k_BT_g is determined to be not equal to the actual activation energy, we do find that an apparently general nonlinear relation between m_s and holds to a good approximation for a large class of polymer models, . The predicted ranges of m_s and are consistent with experimental estimates for high molecular-mass polymer, oligomeric, small molecule, and atomic glass-forming liquids. In particular, relatively high values of m_s are found for polymers having complex monomer structures and significant chain stiffness. The variation of m_s with molecular mass, chain stiffness, and intermolecular interaction strength can be traced to the variation of , which is shown to provide a measure of packing frustration defined in terms of the dimensionless thermal expansion coefficient and isothermal compressibility. The often relatively high fragility and large extent of cooperative motion are found in the GET to derive from the often relatively large packing frustration in this class of polymer glass-forming liquids. Finally, we also develop a tentative model of the "dynamical segmental relaxation time" based on the GET, in which the polymers on a coarse-grained scale are modeled as strings of structureless "beads", as assumed in the Rouse and reptation models of polymer dynamics.

Stimuli-responsive polymers have garnered significant attention for their ability to adapt to environmental changes, offering applications in sensing, smart coatings, and adaptive devices. However, challenges remain in developing multifunctional polymers that combine dynamic responsiveness with robust mechanical properties. In this study, we design and synthesize multifunctional azobenzene-based copolymers, poly(thiourea triethylene glycol)-co-azobenzene (PTUEG₃-co-Azo) copolymers, through a controlled polycondensation process to address these limitations. The flexible PTUEG₃ backbone, with its strong hydrogen-bonding networks, is combined with azobenzene moieties to impart thermal isomerization, acid-base responsiveness, and enhanced adhesion performance. The azobenzene groups exhibited thermally induced cis-to-trans isomerization, leading to structural reorganization, increased molecular packing, and elevated glass transition temperatures (T_g). Additionally, the azobenzene moieties demonstrated reversible acid-base responsiveness, undergoing distinct and repeatable color changes upon protonation and deprotonation. By balancing the flexibility of the PTUEG₃ backbone with the rigidity of azobenzene groups, PTUEG₃-co-Azo copolymers achieved strong adhesion performance and tunable dynamic properties. The 4 : 1 PTUEG₃-co-Azo composition demonstrated superior adhesive strength, attributed to the synergistic effects of hydrogen bonding and azobenzene-induced reorganization under thermal activation. These results present PTUEG₃-co-Azo as a versatile material, bridging the gap between dynamic responsiveness and mechanical robustness, with potential applications in smart sensing, adhesives, and functional coatings.

Dense suspensions often exhibit shear thickening, characterized by a dramatic increase in viscosity under large external forcing. This behavior has recently been linked to the formation of a system-spanning frictional contact network (FCN), which contributes to increased resistance during deformation. However, identifying these frictional contacts poses experimental challenges and is computationally expensive. This study introduces a graph neural network (GNN) model designed to accurately predict FCNs by two dimensional simulations of dense shear thickening suspensions. The results demonstrate the robustness and scalability of the GNN model across various stress levels (σ), packing fractions (ϕ), system sizes, particle size ratios (Δ), and amounts of smaller particles. The model is further able to predict both the occurrence and structure of a FCN. The presented model is accurate and interpolates and extrapolates to conditions far from its control parameters. This machine learning approach provides an accurate, lower cost, and faster predictions of suspension properties compared to conventional methods, while it is trained using only small systems. Ultimately, the findings in this study pave the way for predicting frictional contact networks in real-life large-scale polydisperse suspensions, for which theoretical models are largely limited owing to computational challenges.

Transforming polyolefins (POs), such as polyethylene (PE), into vitrimers is a promising research field due to their low cost, high availability, and excellent chemical resistance and mechanical properties. In these systems, the introduction of dynamic crosslinking can affect the degree of crystallinity in POs and may lead to phase separation due to incompatibility between the PO matrix and crosslinking agents, both of which can impact mechanical performance. This study investigates the relationship between crystallinity, crosslinking, and thermal-mechanical properties in commodity PE-derived vitrimers utilizing reactive 8-arm polyhedral oligomeric silsesquioxane (POSS) nanoparticles by deconvoluting the crosslinked and non-crosslinked components. Specifically, the insoluble crosslinked components displayed a lower modulus and increased brittleness, while the non-crosslinked phase performed similarly to neat PE. Together, the PE-vitrimer, crosslinked with 8-arm POSS, exhibited reduced toughness, elongation at break, and a slight increase in ultimate tensile strength. These behaviors were consistent when comparing the crosslinking density and gel fraction with a bifunctional crosslinker analogue. This work demonstrates the influence of multi-arm, nanoparticle-based crosslinker content on the mechanical properties of semi-crystalline PO-vitrimers, elucidating the roles of network density and crystallinity in determining their performance.

The phase transition mechanism of isotactic polybutene-1 (iPB-1) has always been a central research topic in the fields of polymer physics and industrial application. Phase transition kinetics of the flow-induced oriented form II is significantly faster than the isotropic form II that crystallizes under quiescent condition. In this study, combining the in situ X ray diffraction technique and a homemade extensional rheometer, the influence of amorphous region on the transformation kinetics was been investigated. Results indicated that annealing above the melting temperature (T_m) decreased the phase transition rate, while annealing below the T_m exhibited no obvious impact on the phase transition rate when the annealing time was only 5 min. However, prolonging the annealing time significantly reduced the phase transition kinetics. Remarkably, the crystallinity remained constant during the annealing process, while it exhibited an increase during the subsequent cooling process. The SAXS measurements showed that long spacing decreased after annealing. It is speculated that extended chains in the amorphous region are relaxed and shortened during the annealing process. This work recommends the rapid cooling of iPB-1 products in industrial manufacturing to prevent the relaxation of amorphous chains and promote the phase transition process.

A novel family of symmetric squaramide-based LMWGs has been synthesised, functionalized with both dansyl moieties and alkyl chain spacers of different lengths (n = 3 and n = 4 named L1 and L2, respectively). L1 and L2 are able to form hydrogels in the DMSO : H₂O mixture in different ratios and concentrations. The gels obtained were characterized by means of rheology, TEM and small angle X-ray scattering (SAXS). Afterwards, the adsorption properties of these materials were studied and the gels were used for the removal of dyes, in particular Nile Blue A, Rose Bengal and Naphthol Yellow S from water samples. The reported results demonstrated the potential use of these materials for the removal of dyes in real polluted water matrices.

Over the last decade, the field of programmable self-assembly has seen an explosion in the diversity of crystal lattices that can be synthesized from DNA-coated colloidal nanometer- and micrometer-scale particles. The prevailing wisdom has been that a particular crystal structure can be targeted by designing the DNA-mediated interactions, to enforce binding between specific particle pairs, and the particle diameters, to control the packing of the various species. In this article, we show that other ubiquitous nonspecific interactions can play equally important roles in determining the relative stability of different crystal polymorphs and therefore what crystal structure is most likely to form in an experiment. For a binary mixture of same-sized DNA-coated colloidal micrometer-scale particles, we show how changing the magnitudes of nonspecific steric and van der Waals interactions gives rise to a family of binary body-centered tetragonal crystals, including both cesium-chloride and copper-gold crystals. Simulations using pair potentials that account for these interactions reproduce our experimental observations quantitatively, and a theoretical model reveals how a subtle balance between specific and nonspecific forces determines the equilibrium crystal structure. These results highlight the importance of accounting for nonspecific interactions in the crystal-engineering design process.

The field of cultural heritage conservation science has seen significant advancements over recent decades, particularly through the application of soft matter and colloid science. Gels, nanostructured fluids, nanoparticles, and other advanced functional materials have been developed to address challenges in cleaning, consolidation, and protection of art. More recently, the focus has shifted toward "green" materials and sustainable practices, aligning with broader trends in science and technology. This emphasis on sustainability has revealed the immense potential for cross-disciplinary exchange between conservation science and fields like drug delivery, the food industry, tissue engineering, and more. A clear example of this synergy is seen in the cleaning of artworks, where bio-derived surfactants and biomaterials are increasingly incorporated into microemulsions and gels. These innovations not only enhance cleaning efficacy but also align conservation practices with sustainable principles, drawing parallels to research in cosmetics, pharmaceuticals, and detergents. The examples and materials discussed in this contribution illustrate how advancements in art conservation science can foster mutual technological transfer with other industries. By leveraging the central role of soft matter and colloids, these collaborations produce sustainable solutions that can address critical societal, environmental, and economic challenges.