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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...

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.

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.