Hydrogen‐bonded organic frameworks (HOFs) possess various merits, such as high porosity, tunable structure, facile modification, and ready regeneration. These properties have yet to be explored in ...the context of new functional HOF materials. The facile and inexpensive electrophoretic deposition (EPD) method applied in this study generated a transparent HOF film at room temperature in just 2 min and is applicable to other HOFs. The resulting film exhibited reversible electrochromism with the advantage of long cycle life (>500 cycles). More strikingly, this all‐organic film could be readily regenerated (through rinsing with DMF and redeposition) and showed tunable electrochromic behavior (through low‐cost postsynthetic modification) with the ability to undergo successive color changes, which is difficult to achieve with conventional electrochromic materials. An electrochromic device was manufactured to further demonstrate the application potential of the film.
Facile and efficient electrophoretic deposition was used to prepare an electrochromic hydrogen‐bonded organic framework film (see picture), which exhibited reversible electrochromism with the advantages of long cycle life, ready regeneration, and tunable electrochromic behavior. An electrochromic device was manufactured with the film to further demonstrate its application potential.
This work reports the kinetics of anionic ring‐opening polymerization of hexaethylcyclotrisiloxane (D3Et) with potassium trimethylsilanolate as initiator and diglyme and N,N‐dimethylformamide (DMF) ...as promoters. The polymerization rate of D3Et is influenced by the nature of promoters and the reaction temperatures. With the use of DMF as a promoter, the polymerization activation energy is 107.89 kJ/mol, and the polymerization rate constant at 110°C is 0.08466 min−1 with P/I = 3.0. Gel permeation chromatography and 29Si NMR spectra showed that the intermolecular redistribution occurred during the late stage of polymerization, which facilitated the synthesis of high‐molecular‐weight polydiethylsiloxane (PDES). Differential scanning calorimetry analysis showed that PDES exhibited a glass transition temperature of −142°C and complex crystallization phenomena. Thermogravimetric analysis illustrated that the PDES that was prepared using this method had good thermal stability with onset decomposition temperatures of 483 and 452°C under nitrogen and air conditions, respectively. This work presents innovative approaches for achieving a more energy‐efficient synthesis of PDES to meet the demands of industrial‐scale production.
Synthesis of high molecular weight of polydimethylsiloxane with the backbiting and intermolecular redistribution suppressed.
Polysiloxane dielectric elastomers have garnered a considerable deal of attention over the last decade due to their potential as electroactive soft materials. However, the intrinsic low dielectric ...constant of polysiloxanes has proven a serious limitation in their practical use. In this work, we controlled the dielectric properties of silicone rubber composites by changing the type and content of oxide fillers. The silicone‐based dielectric elastomers with a high dielectric constant (5.21@1 kHz), low modulus (1.62 MPa), and high elongation (1100%) were successfully obtained. The effects of different types of metal oxides on the dielectric properties and mechanical properties of the prepared composites are further explored. Due to their excellent comprehensive features, these types of materials are expected to be applied in capacitive sensors, actuators, generators, and beyond.
Dielectric performance of silicone rubber enhanced by metal oxides.
We consider boundary output feedback stabilization for a one-dimensional anti-stable wave equation subject to general control matched disturbance. The active disturbance rejection control (ADRC) ...approach is adopted in investigation. Using the output of the system, we first design a variable structure unknown input type state observer which is shown to be exponentially convergent. The disturbance is estimated, in real time, through an extended state observer for an ODE reduced from the PDE observer. The disturbance is then canceled in the feedback loop by its approximated value. The stability of the resulting closed-loop system is proven. Simulation results are presented to validate the theoretical conclusions and to exhibit the peaking value reduction by time varying gain instead of constant high gain.
The global spread of SARS-CoV-2 is posing major public health challenges. One feature of SARS-CoV-2 spike protein is the insertion of multi-basic residues at the S1/S2 subunit cleavage site. Here, we ...find that the virus with intact spike (Sfull) preferentially enters cells via fusion at the plasma membrane, whereas a clone (Sdel) with deletion disrupting the multi-basic S1/S2 site utilizes an endosomal entry pathway. Using Sdel as model, we perform a genome-wide CRISPR screen and identify several endosomal entry-specific regulators. Experimental validation of hits from the CRISPR screen shows that host factors regulating the surface expression of angiotensin-converting enzyme 2 (ACE2) affect entry of Sfull virus. Animal-to-animal transmission with the Sdel virus is reduced compared to Sfull in the hamster model. These findings highlight the critical role of the S1/S2 boundary of SARS-CoV-2 spike protein in modulating virus entry and transmission and provide insights into entry of coronaviruses.
Electrochromic technology offers exciting opportunities for smart applications such as energy‐saving and interactive systems. However, achieving dual‐band regulation together with the multicolor ...function is still an unmet challenge for electrochromic devices. Herein, an ingenious electrochromic strategy based on reversible manganese oxide (MnO2) electrodeposition, different from traditional ion intercalation/deintercalation‐type electrochromic materials is proposed. Such a deposition/dissolution‐based MnO2 brings an intriguing electrochromic feature of dual‐band regulation for the ultraviolet (UV) and visible lights with high optical modulation (93.2% and 93.6% at 400 and 550 nm, respectively) and remarkable optical memory. Moreover, a demonstrative smart window assembled by MnO2 and Cu electrodes delivers the electrochromic properties of effective dual‐band regulation accompanied by multicolor changes (transparent, yellow, and brown). The robust redox deposition/dissolution process endows the MnO2‐based electrochromic device with excellent rate capability and an areal capacity of 570 mAh m−2 at 0.1 mA cm−2. It is believed that the metal oxide‐based reversible electrodeposition strategy would be an attractive and promising electrochromic technology and provide a train of thought for the development of multifunctional electrochromic devices and applications.
A novel electrochromic strategy based on reversible manganese oxide (MnO2) electrodeposition is demonstrated, in which the robust deposition/dissolution process endows the MnO2‐based device with selective dual‐band regulation in ultraviolet–visible regions, remarkable optical memory, multicolor changes (transparent, yellow, and brown), in addition to high rate capability and superior energy storage capacity.
Summary
In this article, we are concerned with the error feedback regulator design for a one‐dimensional anti‐stable wave equation with harmonic reference signal and distributed disturbance. By the ...tracking error of the left end displacement, we first introduce a transport equation and a transformation to transform the original wave system to an auxiliary system, where the displacement at the left end is a scaling of the tracking error of the original system. Then an adaptive error‐based observer is designed by using the tracking error to estimate the state of the auxiliary system and unknown amplitudes of the harmonic disturbance and reference signal. Next we propose an observer‐based error feedback controller to regulate the tracking error to zero asymptotically and keep all the states uniformly bounded. Finally some numerical results are presented to illustrate the effectiveness of the controller.
This paper considers the adaptive error feedback regulation problem for a one-dimensional heat equation with general harmonic disturbance anticollocated with control. We first construct an auxiliary ...system in which the control and the anticollocated disturbance become collocated and the measured error becomes the output. Then, we design an error feedback adaptive servomechanism for this system, which includes estimators for the parameters characterizing the disturbance and the reference signals. The control is thus designed to regulate the tracking error to zero and keep the states bounded.
To explore a potential method for improving the toughness of a polylactide (PLA), we used a thermoplastic polyurethane (TPU) elastomer with a high strength and toughness and biocompatibility to ...prepare PLA/TPU blends suitable for a wide range of applications of PLA as general-purpose plastics. The structure and properties of the PLA/TPU blends were studied in terms of the mechanical and morphological properties. The results indicate that an obvious yield and neck formation was observed for the PLA/TPU blends; this indicated the transition of PLA from brittle fracture to ductile fracture. The elongation at break and notched impact strength for the PLA/20 wt %TPU blend reached 350% and 25 KJ/m², respectively, without an obvious drop in the tensile strength. The blends were partially miscible systems because of the hydrogen bonding between the molecules of PLA and TPU. Spherical particles of TPU dispersed homogeneously in the PLA matrix, and the fracture surface presented much roughness. With increasing TPU content, the blends exhibited increasing tough failure. The J-integral value of the PLA/TPU blend was much higher than that of the neat PLA; this indicated that the toughened blends had increasing crack initiation resistance and crack propagation resistance.
In recent years, polysiloxane dielectric elastomers (DEs) have attracted extensive attention, but their low dielectric constant and electrical breakdown strength are the main factors that limit their ...wide application. In this work, we report the effects that a high content of hydrophobic silica has on the dielectric properties and dielectric relaxation behavior of polymethylphenylsiloxane (PMPS). Introducing a high content of hydrophobic silica into PMPS composites increased the dielectric constant of PMPS composites from 3.11 to 3.70 and the breakdown strength of PMPS composites from 35.31 to 42.66 kv/mm. The high content of hydrophobic silica is beneficial for restraining or delaying the occurrence of direct current (DC) conductivity and for effectively reducing the dielectric loss of composites in high temperature and low‐frequency regions. The high content of hydrophobic silica also produces interfacial polarization in the composites, and this increases the dielectric constant and dielectric loss in the high frequency and low‐temperature regions. The dielectric relaxation behavior of PMPS composites was studied in detail using broadband dielectric spectroscopy (BDS) and thermally stimulated depolarization current (TSDC) to better understand the effect of hydrophobic silica on dielectric properties. This work opens a new way to design and prepare polysiloxane‐based materials that have a high dielectric constant, low dielectric loss, and high breakdown strength.
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