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Achieving both higher performance and faster recycling is the target of developing self-healable and malleable epoxy resins. Herein, 1,4,5-oxadithiepane-2,7-dione (DSAA) was synthesized to be the cocuring agent with methylhexahydrophthalic anhydride for constructing new epoxy resins with dynamic and permanent cross-linked network. Through adjusting the weight ratio of two curing agents, the developed epoxy resin exhibits high mechanical and thermal properties as well as excellent malleability and reversible self-healing ability. For the resin (Ep3) containing 22.7 wt % of DSAA, its fracture toughness reaches 1.25 ± 0.08 MPa m1/2. After heating at 160 °C for 1 h, the self-healing efficiency of Ep3 is 96% and glass transition temperature of remolded Ep3 is still as high as 110 °C, and Ep3 is recycled completely after staying at 140 °C for only 0.5 h with the aid of catalytic amount of 4-dimethylaminopyridine and triphenylphosphine. These outstanding integrated performances demonstrate that Ep3 is beneficial...

This paper presents the instability mechanism of an innovative Rhombic Grid Hyperboloid-Latticed Shell (RGHLS) under vertical load through experimental and numerical investigations. The RGHLS is only composed of bidirectional inclined primary and secondary columns without any circumferential members or lateral braces in its radial direction along its height. Therefore it would likely fail by out-of-plane multi-column interaction instability and the corresponding load-carrying capacity should be predicted. The experimental investigation of a reduced-scale test model of RGHLS was firstly performed to study its vertical load-carrying capacity and the multi-column interaction instability. A special spatial beam-string device for vertical multi-point loading of the test model has been initially designed and fabricated to precisely distribute the concentrated load to the top of the columns according to proportional distribution of loads required by designers. The experimental results revealed that the inclined columns indeed exhibited strong mutual restraining actions, and the ratio of the actual ultimate load-carrying capacity of the test model to its design load was 3.37, indicating a reasonable safety margin. In addition, FE numerical results of the test model corresponded well with the experimental results. Ultimately, additional FE numerical analyses have been conducted on the test model. Accordingly the effects of the ratio of stiffness between the secondary and primary columns, overall initial geometric imperfection, in-plane stiffness of top ring beam, and dimensions of portal columns on the load-carrying capacity and failure mode of RGHLS have been investigated extensively. As a result, the ratio of stiffness between the secondary and primary columns has been particularly recommended within a range of 0.46–0.70, so as to eliminate premature failure of X-joints prior to the instability of columns in the prototype of RGHLS.

The rapid development of flexible transparent electronic devices puts forward more requirements for substrate materials, not only including high transparency, but also possessing good self-healing ability, high mechanical strength and toughness. Herein, a urea-containing chain-extended polydimethylsiloxane (LPx) was first designed and synthesized to construct dynamic physical crosslinks induced by hydrogen bonds. Subsequently, multi-amino terminated hyperbranched polysiloxane (HPSi) was selected as the permanent chemical crosslinking point and connected with LPx through isocyanate with controlled exchangeable aliphatic disulfide (SS-NCO). Consequently, a series of LPx-SS-HP films with hierarchical crosslinked networks and dual dynamic bonds are developed. The chain-extension degree of LPx has been proved to play a key role in adjusting the mechanical, thermal and self-healing properties. Among the serial films, LP2-SS-HP shows the best comprehensive properties, of which the glass transition temperature (Tg), tensile strength, Young's modulus and toughness are as high as 96 °C, 8.6 ± 0.6 MPa, 188.5 ± 11.2 MPa and 16.3 ± 0.2 MJ m−3, respectively. Besides, its outstanding flexibility could generate reversible shape changes from folding to bending and scrolling. After three scratching-healing cycles, the healing efficiency of LP2-SS-HP at the same location is still above 90% and the transmittance at 550 nm is as high as 88.6%. These remarkable properties demonstrate that LP2-SS-HP is a high performance scrollable and foldable substrate for fabricating transparent healable electrodes.

The rhombic grid hyperboloid-latticed shells (RGHLSs) in the China Comic and Animation Museum (CCAM) are located on the ground floor, and they sustain enormous vertical and horizontal loads induced from upper building structures on top of them. Each RGHLS consists of numerous bidirectional inclined major and secondary columns that intertwine with one another to form a rhombic grid with X-shaped joints. Without both horizontal circumferential members and horizontal lateral braces in the radial direction of the RGHLS, as well as the existence of significant difference of compressive stiffness between major and secondary columns, the RGHLS would ultimately fail in a complicated form of in-plane and out-of-plane multi-column interaction instability in addition to its overall twist deformation under relatively low vertical loads. Currently, no design method for estimating its design strength and safety is available. Therefore, the load-carrying capacity of the RGHLS must be examined experimentally. This paper selects the RGHLS denoted by Y4 in the structure of the CCAM as the prototype, and presents an experimental investigation of its reduced scale (1:1/4) test model. A loading protocol consisting of six loading phases has been devised in order to predict the static vertical and horizontal load resistance, and horizontal hysteretic response of the RGHLS by keeping the amplitudes of the vertical load constantly as 1.0, 1.4 and 1.6 times the vertical design load of the reduced-scale test model, respectively. The experimental results obtained indicate that the test model remains elastic under 1.8 times its design loads, which is commonly adopted as static structural strength limit in practical design in China. In addition, horizontal cyclic load test indicated that the reduced-scale test model demonstrated sufficiently large horizontal load-carrying capacity as well as exhibited stable and ample hysteretic curves even under 1.6 times vertical load actions without any obvious stiffness reductions. This study comprehensively introduces the experimental test schemes and deeply analyzes the experimental results, thus forming an important basis for designing the load-carrying capacity of such RGHLSs. Ultimately, according to the experimental loading protocol, numerical simulations and analyses of the test model have been conducted by adopting ANSYS 12.1. The interaction strength design curve of the test model under a combination of vertical and horizontal loads is also proposed by carrying out additional numerical simulations of the model. The FE and experimental results have been compared, and they correspond well to one another, indicating that the results of the reduced-scale test model are accurate enough and reliable.

A new type of core-separated buckling-restrained braces, namely a core-separated battened buckling-restrained brace (B-BRB) has been proposed. Its load-carrying capacity and hysteretic response are investigated theoretically and experimentally in this paper. The B-BRB has a remarkable advantage over a common buckling-restrained brace (BRB), in which the newly formed cross-section of the B-BRB is spread outwards by spacing two cores, hence resulting in higher material utilization efficiency in its structural design. In addition, the two independent all-steel BRBs, each having a single plate core simply in-filled in a narrow hollow section, are connected by longitudinally distributed battens rather than continuous plates. Based on the elastic-plastic FE analysis of a B-BRB under monotonic compressive load, its ultimate resistance and failure modes are investigated numerically, considering the effect of its overall initial geometric imperfection. An interaction formula between normalized slenderness ratio and buckling factor of the B-BRB is proposed for predicting its ultimate load-carrying capacity. Consequently, the hysteretic response of the B-BRB is explored through elastic-plastic FE analysis. The maximum normalized slenderness ratios of the B-BRBs required for a load-bearing type and an energy-dissipation type are proposed in their strength designs, respectively. Ultimately, hysteretic responses of five B-BRB specimens have been experimentally investigated. The experimental results are compared with the FE numerical analysis, which considers plate local buckling of all components of the B-BRBs. The comparison has verified the rationality of the proposed design method.

Developing a multi-functional coating with high mechanical strength, and reversible self-healing and antibacterial ability has become an effective strategy for preventing the severe threat to human health posed by biofilm contamination. Herein, a novel linear polyacrylate resin (LP) containing pendent sulfobetaine and acetoacetyloxy groups was designed and synthesized, and was subsequently reacted with hyperbranched polysiloxane terminated by multi-amine (HPSi) to form dynamic vinylogous urethane groups. The resultant novel multi-functional crosslinked polyacrylate coating (LP-HP) shows high mechanical strength, and outstanding reversible self-healing and remarkable antibacterial ability. The concentration of HPSi in the polyacrylate coating is systematically researched and proved to play a key role in adjusting the mechanical, thermal and self-healing properties. For the polyacrylate coating (LP-HP6) containing 6.3 wt% of HPSi, its tensile strength and toughness are as high as 17.89 ± 0.42 MPa and 5.72 ± 0.32 MPa, respectively. The self-healing efficiency of LP-HP6 is higher than 92% under mild conditions (maintained at 60 °C for 24 h). This is ascribed to the unique configuration of HPSi that is rich in amine groups and has fewer chain entanglements to facilitate easier segmental motion. Furthermore, the surface of LP-HP6 exhibits high resistance to the adhesion of E. coli and S. aureus with antibacterial rates above 95%, originated from the nonspecific and nontoxic sulfobetaine groups immobilized in the main chain via convenient copolymerization. These excellent properties demonstrate that LP-HP coatings have great potential applications to resist biofilm contamination in architectural ornament, medical engineering, food and pharmaceutical fields.

Grid Cylindrical-Lattice Shells (GCLSs) have found their wide application in high-rise buildings and TV towers as the outer cylindrical frame of tube-in-tube structures subjected mainly to axial compression. This paper presents the elastic buckling behaviour of Grid Cylindrical-Lattice Shells (GCLSs) under axial compression. Because of a lack of lateral braces in the radial direction of the GCLS along its height, the GCLS tends to fail by two buckling modes under axial compression, namely global flexural buckling and circumferential multi-wave buckling. First, the fundamental three-story GCLS is investigated by using the energy method. The restraining action of the ring beam on the columns in the two buckling modes is explored separately, and this exploration leads to the radial rotational restraint stiffness, tangential rotational restraint stiffness and translational restraint stiffness of the ring beams, denoted by βr, βt and α, respectively; in addition, the corresponding elastic buckling loads of the three-story GCLS in the two buckling modes are separately derived. Then, based on the three key parameters, simple fitting formulas are developed to separately predict the elastic buckling loads of the multi-story GCLS in the two buckling modes. This outcome provides fundamentals for further establishing load-carrying capacity design of GCLSs under axial compression.

Surface icing and delamination damage have been tough problems of outdoor devices and equipment in many fields including aerospace, new energy and electronics. Herein, one new thermally resistant tri-layered composites with superhydrophobic surface and great self-healing after complete fracture were fabricated based on self-healable epoxy resin (hEP), multiwalled carbon nanotubes (CNTs) and superhydrophobic copper powders (nCu). Integrated properties of composites are greatly associated with the loading of CNTs. The composite with 10 wt% CNTs (nCu-CNT3/hEP-hEP) shows excellent superhydrophobicity, and its glass transition temperatures of bottom layer (hEP) and interlayer (CNT3/hEP) are as high as 110–113 °C, guaranteeing the dimensional stability during Joule heating. Under a voltage of 10 V, ice blocks on nCu-CNT3/hEP-hEP melt within 26 s and rolled off from the superhydrophobic surface with a 5° horizontal tilt. Besides, two pieces obtained by cutting a whole block of nCu-CNT3/hEP-hEP composite were replanted to produce a perfect block of the composite after staying at 160 °C for 1 h; moreover, the healed composite also exhibits excellent superhydrophobicity, proving good abilities to ensure lifespan of related products. The mechanism behind these remarkable properties of nCu-CNT3/hEP-hEP properties was elucidated.

In the past several decades, a great deal of attention has been focused on the control of light emission of luminescent materials. Compared to our previous work on an aggregation-induced emission (AIE) initiator, an aggregation-caused quenching (ACQ) initiator (TPP-A) has been successfully synthesized and acted as an initiator of atom transfer radical polymerization (ATRP). Four end-functionalized polymers, PS-A, PS-NI, PNIPAM-A and PNIPAM-NI, were obtained using TPP-A or TPP-NI as an initiator via ATRP. TPP-A exhibits a weak charge transfer (CT) and ACQ, but TPP-NI possesses a strong CT and AIE. After two initiators were introduced to polystyrene (PS) chains, the CT of PS-A and PS-NI are well-preserved, but their photoluminescence (PL) intensity is increased because the PS chains could separate initiators from intermolecular interactions and restrict their intramolecular rotations. However, the emission behaviours of PNIPAM-A are different from those of PS-A due to the high polarity of the PNIPAM chain. When the temperature of the solution for PNIPAM-A is above the lower critical solution temperature (LCST), the PNIPAM-A solution possessed higher emission intensities than those measured at room temperature due to the decrease the polarity of the PNIPAM chain and the emission behaviours of PNIPAM-NI are similar to that of PS-NI.

4-(3-(4-(Dimethylamino)phenyl)acryloyl)phenyl-2-bromo-2-methylpropanoate (APPBr) was used for the heterogeneous atom transfer radical polymerization (ATRP) of styrene (St) with copper(I) bromide/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) catalytic system. The functional end group was characterized via UV-Vis and 1H NMR spectra. The polymerization showed a first-order kinetic characteristic and each of the obtained polymers had well-controlled molecular weight and relatively low polydispersity index (PDI). Furthermore, the obtained end-functionalized polystyrene (PS) in solution showed strong green-light emission which is further affected by mixing different metal cations. In particular, the fluorescent intensity of the polymer was decreased in the presence of Ag+, Cu2+ and Fe3+.

Aggregated or solid state red fluorescent materials with efficient light emission are rare but have wide applications in optoelectronic and biological fields. Herein, two pyran derivatives, EtAmPy and EtOxPy with different charge transfers (CT), were designed as initiators and introduced to polystyrene chains via atom transfer radical polymerization (ATRP). The emission of EtAmPy was quenched both in highly polar solvents and in an aggregated state because of its strong CT and intermolecular interactions, respectively. After EtAmPy was introduced to normal polystyrene chains, the obtained functional PS emitted strong red light with a quantum yield of 37% in an aggregated state. Differently from EtAmPy, EtOxPy, possessing a weak CT and not being sensitive to the change of microenvironment, was AIE-active and displayed a large red shift in emission spectra in an aggregated state. Meanwhile, the functional PS initiated by EtOxPy showed obviously blue-shifted emission, compared to its initiator, in an aggregated state by reducing their intermolecular interactions. EtAmPy-functionalized polystyrene showed a successful application in cell imaging. Therefore, using the CT effect in molecular design and polymerization is beneficial to obtaining new red emission probes.

A new hydrazine naphthalimide initiator (NI) was designed and synthesized. Two end functional group polymers NPVCz-1 and NPVCz-2 were prepared by ATRP. We successfully controlled the location of the naphthalimide functional group at one end of the polymer chain. NPVCz-1 and NPVCz-2 were fabricated as films by simple spin-coating and all of them were then prepared as sandwich memory devices ITO/NPVCz-1/Al and ITO/NPVCz-2/Al respectively. According to the measurements, all devices exhibited stable binary flash-type memory effects. In addition, ITO/NPVCz-1/Al and ITO/NPVCz-2/Al exhibited different turn-on threshold voltages of about −2.5 and −1.5 V respectively. It illustrated that NPVCz-2 possessing a larger molecular weight shows lower turn-on threshold voltage due to the lower hole injection barrier, which was related to low-power consumption.

The emission behavior of a new V-shaped organic fluorescent compound (p,p′-bis(2-aryl-1,3,4-oxadiazol-5-yl)diphenyl sulfone (OZA-SO)), consisting of diethylamino (donor) and sulfone (acceptor) units, has been studied in various polar solvents and with different morphologies. As expected, there is the gradual transition from the locally excited state to the intramolecular charge-transfer (ICT) state with the increasing solvent polarity. The photoluminescence intensity of OZA-SO initially decreases with a low water fraction (f(w)), owing to ICT effect, and then increases with a high f(w), owing to crystallization-induced emission enhancement. At the same time, the fluorescence lifetime of OZA-SO increases from 0.062 ns in dimethylformamide (DMF) to 5.80 ns in a solution containing 90 % water, and then to 7.49 ns in a solution containing 60 % water. Furthermore, the solid-state emission of OZA-SO can be tuned reversibly from green to yellow by fuming/grinding or fuming/heating owing to morphological changes. This color-switchable feature of OZA-SO may have potential applications in optical-recording and temperature-sensing materials.