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Photoisomerization and photoluminescence are two distinct energy dissipation pathways in light‐driven molecular motors. The photoisomerization properties of discrete molecular motors have been well established in solution, but their photoluminescent properties have been rarely reported—especially in aggregates. Here, it is shown that an overcrowded alkene‐based molecular motor exhibits distinct dynamic properties in solution and aggregate states, for example, gel and solid states. Despite the poor emissive properties of molecular motors in solution, a bright emission is observed in the aggregate states, including in gel and the crystalline solid. The emission wavelength is highly dependent on the nature of the supramolecular packing and order in the aggregates. As a result, the fluorescent color can be readily tuned reversibly via mechanical grinding and vapor fuming, which provides a new platform for developing multi‐stimuli functional materials. [ABSTRACT FROM AUTHOR]

A non-equilibrium cucurbit[7]uril-mediated supramolecular host–guest system is fabricated by using urea/urease to control aqueous solution pH on time dimension, showing transient assembly behavior and time-dependent fluorescence. The dynamic assembly can be also achieved in hydrogel network, resulting in a time-dependent fluorescent hydrogel for information encryption. [ABSTRACT FROM AUTHOR]

Facile fabrication, low material complexity and closed‐loop recycling are essential for polymer plastics to alter their linear product economy towards a cradle‐to‐cradle one. Covalent adaptable networks (CANs) are one way to achieve that, which intrinsically exhibit decent mechanical properties like the thermosets but could also be easily recycled like the thermoplastics. In this work, we introduce rigid ester structural motifs into dynamic poly(disulfide)s to form a series of dual polymer networks. Owning to the coherence of soft/rigid segments and the reversible sacrificial crosslinking, they exhibit tailorable mechanical properties and good resistance towards different chemicals. Their closed‐loop recycling is achieved via mild solvolysis, maintaining materials' mechanical integrities. It offers a solution as a sustainable replacement for engineering plastics which are massively under production but hard to be recycled. [ABSTRACT FROM AUTHOR]

Covalent adaptable networks (CANs), leveraging the dynamic exchange of covalent bonds, emerge as a promising material to address the challenge of irreversible cross‐linking in thermosetting polymers. In this work, we explore the introduction of a catalyst‐free and associative C=C/C=N metathesis reaction into thermosetting polyurethanes, creating CANs with superior stability, solvent resistance, and thermal/mechanical properties. By incorporating this dynamic exchange reaction, stress‐relaxation is significantly accelerated compared to imine‐bond‐only networks, with the rate adjustable by modifying substituents in the ortho position of the dynamic double bonds. The obtained plasticity enables recycle without altering the chemical structure or mechanical properties, and is also found to be vital for achieving shape memory functions with complex spatial structures. This metathesis reaction as a new dynamic crosslinker of polymer networks has the potential to accelerate the ongoing exploration of malleable and functional thermoset polymers. [ABSTRACT FROM AUTHOR]

Circularly polarized luminescence (CPL) is promising for applications in many fields. However, most systems involving CPL are within the visible range; near‐infrared (NIR) CPL‐active materials, especially those that exhibit high glum values and can be controlled spatially and temporally, are rare. Herein, dynamic NIR‐CPL with a glum value of 2.5×10−2 was achieved through supramolecular coassembly and energy‐transfer strategies. The chiral assemblies formed by the coassembly between adenosine triphosphate (ATP) and a pyrene derivative exhibited a red CPL signal (glum of 10−3). The further introduction of sulfo‐cyanine5 resulted in a energy‐transfer process, which not only led to the NIR CPL but also increased the glum value to 10−2. Temporal control of these chiral assemblies was realized by introducing alkaline phosphatase to fabricate a biomimetic enzyme‐catalyzed network, allowing the dynamic NIR CPL signal to be turned on. Based on these enzyme‐regulated temporally controllable dynamic CPL‐active chiral assemblies, a multilevel information encryption system was further developed. This study provides a pioneering example for the construction of dynamic NIR CPL materials with the ability to perform temporal control via the supramolecular assembly strategy, which is expected to aid in the design of supramolecular complex systems that more closely resemble natural biological systems. [ABSTRACT FROM AUTHOR]

SiC/Al composites are widely used in aerospace and other fields due to their excellent mechanical properties. For large-concentration composites, due to the extremely high proportion of SiC and the unstable interface between the two phases, the SiC particles are broken and detached during the processing, which makes the surface quality of the workpiece insufficient to meet the service requirements. Electrically assisted cutting technology is expected to break through this technical bottleneck. This paper investigates the surface quality of high-concentration SiC/Al grinding with electroassisted biolubricant MQL. The surface morphology after processing is observed. Firstly, by comparing the traditional grinding and electrically assisted grinding conditions, it is found that the fundamental reason for the improvement in the grinding surface quality using a pulse current is the improvement in the Al plasticity. Secondly, based on the thermal effect and non-thermal effect of the pulse current, the influence of the electrical parameters (current, duty cycle and frequency) on the machining indication quality is discussed. It is found that when the current and duty cycle increase, the machining surface quality will also increase, while the frequency change has little effect on the surface quality. Finally, friction and wear experiments are carried out on the grinding surface under different working conditions to explore the friction and wear characteristics of the surface of the workpiece. The results show that the pulse current can significantly improve the wear resistance of the grinding surface. [ABSTRACT FROM AUTHOR]

Since droplet collision with walls has become a research hotspot, scholars have conducted a large number of studies on the dynamic behavior of electrically neutral droplets colliding with dry walls. However, with the rapid development of electrostatic spray technology, there is an increasingly urgent need to study the dynamic process of collision between charged droplets and walls. In this paper, considering the actual working conditions of electrostatic spray, an electric field model is introduced based on the two-phase flow field. Through the coupling of a multiphase flow field and electric field and a multiphysics field, the dynamic numerical calculation method is used to explore the collision electrodynamic behavior of charged droplets and liquid film. The dynamic evolution process of the formation and development of the liquid crown in the collision zone was clarified, and the critical velocity and critical Weber number of the rebound, spreading, and splashing of charged droplets were tracked. The distribution characteristics of electrostatic field, pressure field, and velocity field under different working conditions are analyzed, and the dynamic mechanism of the charged droplet collision liquid film under multi-physics coupling is revealed based on the electro-viscous effect. It is confirmed that the external electric field can increase the critical velocity of droplet splashing and fragmentation and promote the spreading and fusion behavior of droplets and liquid films. The influence of the impact angle of charged droplets on the collision behavior was further explored. It was found that the charged droplets not only have a smaller critical angle for fragmentation and splashing, but also have a faster settling and fusion speed. [ABSTRACT FROM AUTHOR]

Electrostatic atomization minimum quantity lubrication (EMQL) technology has been developed to address the need for environmentally friendly, efficient, and low-damage grinding of challenging titanium alloy materials. EMQL leverages multiple physical fields to achieve precise atomization of micro-lubricants, enabling effective lubrication in high temperature, high pressure, and high-speed grinding environments through the use of electric traction. Notably, the applied electric field not only enhances atomization and lubrication capabilities of micro-lubricants but also significantly impacts heat transfer within the grinding zone. In order to explore the influence mechanism of external electric field on spatial heat transfer, this paper first comparatively analyzes the grinding heat under dry grinding, MQL, and EMQL conditions and explores the intensity of the effect of external electric field on the heat transfer behavior in the grinding zone. Furthermore, the COMSOL numerical calculation platform was used to establish an electric field-enhanced (EHD) heat transfer model, clarifying charged particles' migration rules between poles. By considering the electroviscous effect, the study reveals the evolution of heat transfer structures in the presence of an electric field and its impact on heat transfer mechanisms. [ABSTRACT FROM AUTHOR]

Introducing photo‐responsive molecules offers an attractive approach for remote and selective control and dynamic manipulation of material properties. However, it remains highly challenging how to use a minimal amount of photo‐responsive units to optically modulate materials that are inherently inert to light irradiation. Here we show the application of a light‐driven rotary molecular motor as a "motorized photo‐modulator" to endow a typical H‐bond‐based gel system with the ability to respond to light irradiation and create a reversible sol‐gel transition. The key molecular design feature is the introduction of a minimal amount (2 mol %) of molecular motors into the supramolecular network as photo‐switchable non‐covalent crosslinkers. Advantage is taken of the subtle interplay of the large geometry change during photo‐isomerization of the molecular motor guest and the dynamic nature of a supramolecular gel host system. As a result, a tiny amount of molecular motors is enough to switch the mechanical modulus of the entire supramolecular systems. This study proves the concept of designing photo‐responsive materials with minimum use of non‐covalent light‐absorbing units. [ABSTRACT FROM AUTHOR]