Visible-light-excitable aqueous afterglow exhibiting long emission wavelength and ultralong afterglow lifetime of 7.64 s.

We utilize the dopant-matrix strategy and emulsion polymerization to obtain aqueous afterglow dispersions from a liquid precursor, which avoids the processing of solid materials, protects organic triplets and achieves long phosphorescence lifetime of 7.64 s. The aqueous afterglow dispersions display great potential for biomedical applications due to their ultralong-lived excited states.

Effect of Cosolvent on the Vesicle Formation Pathways under Solvent Exchange Process: A Dissipative Particle Dynamics Simulation.

The effective control over the vesicle formation pathways is vital for tuning its function. Recently, a liquid-liquid phase-separated intermediate (LLPS) is observed before a vesicular structure during the solvent exchange self-assembly of block copolymers. Though the understanding of polymer structures and chemical compositions on the competition between LLPS and micellization has made some progress, little is known about the role of cosolvent on it. In this study, the influence of cosolvent on the vesicle formation pathways is investigated by using dissipative particle dynamics. The results show that the range of water fraction within which the LLPS is favored will be highly dependent on the affinity difference of cosolvent to water and to polymer repeat units. The change of the cosolvent-water interaction and the water fraction impact the distribution of cosolvent in the polymer domain, the miscibility between the components in the system as well as the chain conformations, which finally induce different self-assembly behaviors. Our findings would be helpful for understanding the LLPS and controlling the morphologies of diblock polymers in solutions for further applications.

A DOPO-Based Compound Containing Aminophenyl Silicone Oil for Reducing Fire Hazards of Polycarbonate.

A novel P/N/Si-containing flame retardant (marked as DASO) was synthesized through an Atherton-Todd reaction between 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide and aminophenyl silicone oil, and further used for reducing fire hazards of polycarbonate (PC). The chemical structure of DASO was verified via FTIR, 1H, and 31P NMR. Upon the incorporation of 2 wt% DASO, the FRPC composite achieved a high limiting oxygen index (LOI) of 32.2% and a desired UL-94 V-0 rating. In this case, the peak heat release rate (PHRR) and total smoke production (TSP) were reduced by 26% and 44% as compared with the pure PC, respectively. The improved fire safety contributed to the flame retardant roles of DASO in both the condensed phase and gas phase. The presence of DASO promoted the formation of dense and highly graphited char layer in the condensed phase, and released non-combustible gases and phosphorus-containing radicals in the gas phase. Furthermore, the FRPC composites displayed comparable elongation at break but a slightly reduced tensile and impact strength.

A Nitrogen-Rich DOPO-Based Derivate for Increasing Fire Resistance of Epoxy Resin with Comparable Transparency.

To endow synergistically epoxy resin (EP) with excellent fire resistance and high optical transparency, a nitrogen-rich DOPO-based derivate (named as FATP) was synthesized and incorporated into EP. It showed that the incorporation of the FATP reduced the fire hazard of the EP, as demonstrated by the fact that the EP/4% FATP blends gained a UL-94 V-0 rating and an LOI value of 35%, with the lowest values of the THR (86.7 MJ/m2), the PHRR (1059.3 kW/m2), and the TSP (89.6 MJ/m2). The presence of the FATP also reduced the thermal stability and the crosslinking density whilst improving the curing reaction and the storage modulus of the EP/FATP blends. The TG-FTIR spectra showed that •HPO/•PO free radicals and some nonflammable gases (HN3 and NH3) were produced during the pyrolysis, and the characterization (SEM, Raman spectroscopy, and XPS) of char residues confirmed that the FATP facilitated the formation of continuous and compact carbon layers of greater graphitization degree. It was thus concluded that the FATP played the flame-retardant roles in both the gas and condensed phases. Furthermore, the FREPs kept almost identical transparency as the pristine EP, and mechanical properties were also slightly enhanced. The FREPs presented in this work show promising applications in the fields of advanced optical technology.

Facile Preparation of a Novel Vanillin-Containing DOPO Derivate as a Flame Retardant for Epoxy Resins.

A novel bio-based flame retardant designated AVD has been synthesized in a one-pot process via the reaction of 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO), vanillin (VN), and 2- aminobenzothiazole (ABT). The structure of AVD was confirmed using Fourier transform infrared spectroscopy (FTIR), and 1H and 31P nuclear magnetic resonance spectroscopy (NMR). The curing process, thermal stability, flame retardancy, and mechanical properties of the epoxy resin (EP) modified with AVD have been investigated comprehensively. The extent of curing, the glass transition temperature and the crosslinking density of the blend decreased gradually with increasing AVD content. The thermogravimetric analysis (TGA) was used to demonstrate that the presence of AVD reduced the thermal decomposition rate for EP and enhanced the formation of carbon residue during resin decomposition. A blend of 7.5 wt% AVD (0.52% phosphorus) displays a UL-94V-0 rating and a LOI of 31.1%. Reduction of the peak heat release rate, total heat release rate and total smoke production was 41.26%, 35.70%, and 24.03%, respectively, as compared to the values for pure EP. The improved flame retardancy of the flame retardant epoxy (FREP) may be attributed to the formation of a compact and continuous protective char layer into the condensed phase as well as the release of non-combustible gases and phosphorus-containing radicals from the decomposition of AVD in the gas phase. AVD is a new and efficient biobased flame retardant for epoxy with great prospects for industrial applications.

Preparation of Mn2+ Doped Piperazine Phosphate as a Char-Forming Agent for Improving the Fire Safety of Polypropylene/Ammonium Polyphosphate Composites.

A piperazine phosphate doped with Mn2+ (HP-Mn), as a new char-forming agent for intumescent flame retardant systems (IFR), was designed and synthesized using 1-hydroxy ethylidene-1,1-diphosphonic acid, piperazine, and manganese acetate tetrahydrate as raw materials. The effect of HP-Mn and ammonium polyphosphate (APP) on the fire safety and thermal stability of polypropylene (PP) was investigated. The results showed that the combined incorporation of 25 wt.% APP/HP-Mn at a ratio of 1:1 endowed the flame retardant PP (PP6) composite with the limiting oxygen index (LOI) of 30.7% and UL-94 V-0 rating. In comparison with the pure PP, the peak heat release rate (PHRR), the total heat release (THR), and the smoke production rate (PSPR) of the PP6 were reduced by 74%, 30%, and 70%, respectively. SEM and Raman analysis of the char residues demonstrated that the Mn2+ displayed a catalytic cross-linking charring ability to form a continuous and compact carbon layer with a high degree of graphitization, which can effectively improve the flame retardancy of PP/APP composites. A possible flame-retardant mechanism was proposed to reveal the synergistic effect between APP and HP-Mn.

Manipulation of Organic Afterglow by Thermodynamic and Kinetic Control.

The fabrication of room-temperature organic phosphorescence and afterglow materials, as well as the transformation of their photophysical properties, has emerged as an important topic in the research field of luminescent materials. Here, we report the establishment of energy landscapes in dopant-matrix organic afterglow systems where the aggregation states of luminescent dopants can be controlled by doping concentrations in the matrices and the methods of preparing the materials. Through manipulation by thermodynamic and kinetic control, dopant-matrix afterglow materials with different aggregation states and diverse afterglow properties can be obtained. The conversion from metastable aggregation state to thermodynamic stable aggregation state of the dopant-matrix afterglow materials to leads to the emergence of intriguing afterglow transformation behavior triggered by thermal and solvent annealing. The thermodynamically unfavorable reversible afterglow transformation process can also be achieved by coupling the dopant-matrix afterglow system to mechanical forces.

Cross-Linking Modification of Ammonium Polyphosphate via Ionic Exchange and Self-Assembly for Enhancing the Fire Safety Properties of Polypropylene.

Modified ammonium polyphosphate (MAPP) was prepared as a novel mono-component intumescent flame retardant (IFR) via the ionic exchange between ammonium polyphosphate (APP) and piperazine sulfonate, which is synthesized by self-assembly using 1-(2-aminoethyl) piperazine (AEP) and p-aminobenzene sulfonic acid (ASC) as raw materials. This all-in-one IFR integrating three functional elements (carbon, acid, and gas source) showed more efficient flame retardancy and excellent smoke suppression as well as better mechanical properties than the conventional APP. The incorporation of 22.5 wt.% MAPP into polypropylene (PP) eliminated the melt dripping phenomenon and passed the UL-94 V-0 rating. The results of the cone calorimetry test (CCT) revealed that the release of heat, smoke, and CO is significantly decreased, demonstrating that this novel IFR endows PP with excellent fire safety more effectively. For PP/MAPP composites, a possible IFR mechanism was proposed based on the analysis of the pyrolysis gas and char residues.

Improvement of Exciton Collection and Light-Harvesting Range in Ternary Blend Polymer Solar Cells Based on Two Non-Fullerene Acceptors.

Abstract: A non-fullerene molecule named Y6 was incorporated into a binary blend of PBDB-T and IT-M to further enhance photon harvesting in the near-infrared (near-IR) region. Compared with PBDB-T/IT-M binary blend devices, PBDB-T/IT-M/Y6 ternary blend devices exhibited an improved short-circuit current density (JSC) from 15.34 to 19.09 mA cm-2. As a result, the power conversion efficiency (PCE) increased from 10.65% to 12.50%. With an increasing weight ratio of Y6, the external quantum efficiency (EQE) was enhanced at around 825 nm, which is ascribed to the absorption of Y6. At the same time, EQE was also enhanced at around 600-700 nm, which is ascribed to the absorption of IT-M, although the optical absorption intensity of IT-M decreased with increasing weight ratio of Y6. This is because of the efficient energy transfer from IT-M to Y6, which can collect the IT-M exciton lost in the PBDB-T/IT-M binary blend. Interestingly, the EQE spectra of PBDB-T/IT-M/Y6 ternary blend devices were not only increased but also red-shifted in the near-IR region with increasing weight ratio of Y6. This finding suggests that the absorption spectrum of Y6 is dependent on the weight ratio of Y6, which is probably due to different aggregation states depending on the weight ratio. This aggregate property of Y6 was also studied in terms of surface energy.

One-Step Synthesis of Highly Efficient Oligo(phenylphosphonic Dihydroxypropyl Silicone Oil) Flame Retardant for Polycarbonate.

A highly efficient flame retardant and smoke suppression oligomer, oligo(phenylphosphonic dihydroxypropyl silicone oil) (PPSO), was synthesized by a one-step reaction. The chemical structure of PPSO was confirmed by Fourier transform infrared (FTIR), 31P nuclear magnetic resonance (31P NMR), and 29Si nuclear magnetic resonance (29Si NMR). The flame-retardant effect of PPSO on the polycarbonate (PC) matrix was investigated by limiting oxygen index, UL-94 vertical burning test, and cone calorimetry, respectively. The results showed that PC/PPSO composites passed UL-94 V-0 rate testing with only 1.3 wt. % PPSO. Furthermore, the incorporation of PPSO can suppress the release of smoke. The flame-retardant mechanism was also investigated via thermogravimetric analysis-fourier transform infrared spectroscopy (TG-FTIR), field-emission scanning electronic microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. From the result of pyrolysis gas and char residue, PPSO played a synergistic flame-retardant mechanism including the gas phase and the condensed phase.

Design and Application of Highly Efficient Flame Retardants for Polycarbonate Combining the Advantages of Cyclotriphosphazene and Silicone Oil.

A novel flame retardant (HSPCTP) was successfully designed and incorporated into a polycarbonate (PC) matrix. Combining the advantages of cyclotriphosphazene and silicone oil, PC/HSPCTP composites passed UL-94 V-0 rating testing with only 3 wt% HSPCTP, and their LOI value increased from 25.0% to 28.4%. The findings showed that HSPCTP exhibits both gas-phase and solid-phase flame-retardant effects. Furthermore, the incorporation of HSPCTP into PC could suppress the release of smoke. Finally, the flame-retardant mechanism is discussed in depth.

Facile Preparation of Highly Conductive Poly(amide-imide) Composite Films beyond 1000 S m-1 through Ternary Blend Strategy.

Highly conductive thin films with suitable mechanical performances play a significant role in modern electronic industry. Herein, a series of ternary conductive polymer composites were fabricated by incorporating carbon black (CB) into binary conductive polymer composites of poly(amide-imide) (PAI) and polyaniline (PANI) to enhance their mechanical and conductive properties simultaneously. By varying the composition of PAI/PANI/CB ternary films, the conductivity enhanced by two orders of magnitude compared with the sum of PAI/PANI and PAI/CB binary conductive polymer composites, and a high conductivity of 1160 S m-1 was achieved. The improved conductivity is mainly because much more continuous conductive networks were constructed in the ternary conductive polymer composites. With the help of the unusual morphology, the tensile strength was also enhanced by more than 80% from 21 to 38 MPa. The origin for the improved morphology was discussed for further improvement.

Fabrication of a superhydrophobic mesh based on PDMS/SiO2 nanoparticles/PVDF microparticles/KH-550 by one-step dip-coating method.

In this study, a facile one-step dip-coating approach was reported for fabrication of superhydrophobic copper mesh by using PDMS, SiO2 nanoparticles, PVDF microparticles and a couple agent 3-aminopropyltriethoxysilane (KH-550). It is found that undesirable SiO2 agglomeration was obviously reduced by introducing KH-550 and PVDF microparticles. The KH-550 acts as the bridge-linker and binds SiO2, PVDF and PDMS together. The as-prepared superhydrophobic mesh exhibited a promising water contact angle of 160.1° and a small sliding angle of 2.5°. The coating displayed excellent resistance to various pollutants and retained its superhydrophobicity after abrasions (sandpaper abrasion or adhesive tape tear). The strong chemical stability was also observed when the mesh was immersed in various solutions, especially in neutral and alkaline solutions. The applications of the superhydrophobic mesh for quantitative water droplet manipulation and oil spill cleanup were also illustrated. The method is facile and economic, and could be used for large-scale fabrications for industrial applications.

A glucose modified filter paper for effective oil/water separation.

Efficient and low-cost oil/water separation remains a great challenge for industries. Natural cellulose-based filter paper, because of its abundance, low cost, biodegradability and excellent chemical stability, has been developed as an oil/water separator in recent years. In the present study, a superhydrophilic and underwater superoleophobic filter paper is successfully prepared by an aldol condensation reaction to crosslink glucose molecules with filter paper. The prepared filter paper is characterized by IR-spectroscopy, SEM spectroscopy and wettability measurements, and it has high underwater oil contact angles of over 162° for hexane, toluene and petroleum ether. It is shown that the modified filter paper has high water recovery from various oil/water mixtures, not only in a gentle environment but also in acidic, alkaline, and salty environments and at different temperatures. Moreover, the glucose modified filter paper shows excellent oil/water emulsion separation efficiency (>99%) and good recycling performance. The preparation is economic and could be easily scaled up, suggesting its great potential for large-scale industrial applications.

A facile approach to a silver conductive ink with high performance for macroelectronics.

An unusual kind of transparent and high-efficiency organic silver conductive ink (OSC ink) was synthesized with silver acetate as silver carrier, ethanolamine as additive, and different kinds of aldehyde-based materials as reduction agents and was characterized by using a thermogravimetric analyzer, X-ray diffraction, a scanning electron microscope, and a four-point probe. The results show that different reduction agents all have an important influence on the conductive properties of the ink through a series of complex chemical reactions, and especially when formic acid or dimethylformamide was used as the reduction agent and sintered at 120°C for 30 s, the resistivity can be lowered to 6 to 9 µΩ·cm. Furthermore, formula mechanism, conductive properties, temperature, and dynamic fatigue properties were investigated systematically, and the feasibility of the OSC ink was also verified through the preparation of an antenna pattern.

High-reproducibility, flexible conductive patterns fabricated with silver nanowire by drop or fit-to-flow method.

An unusual strategy was designed to fabricate conductive patterns with high reproducibility for flexible electronics by drop or fit-to-flow method. Silver nanowire (SNW) ink with surface tension of 36.9 mN/m and viscosity of 13.8 mPa s at 20°C was prepared and characterized using a field emission transmission electron microscope, X-ray diffractometer, thermogravimetric analyzer, scanning electron microscope, and four-point probe. Polydimethylsiloxane (PDMS) pattern as template was fabricated by spin coating (500 rpm), baking at 80°C for 3 h, and laser cutting. The prepared SNW ink can flow along the trench of the PDMS pattern spontaneously, especially after plasma treatment with oxygen, and show a low resistivity of 12.9 µΩ cm after sintering at 125°C for 30 min. In addition, an antenna pattern was also prepared to prove the feasibility of the approach.

Postfabrication encapsulation of model protein drugs in a negatively thermosensitive hydrogel.

A postfabrication encapsulation technique was developed for loading model protein drugs into an intelligent and biodegradable hydrogel film, which exhibits negative thermosensitivity with a desirable phase transition temperature between refrigerator temperature and body temperature. The hydrogel comprises mainly poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer, and oligo(lactide). The model proteins Hemoglobin and Bovine Serum Albumin were loaded into the hydrogel films by soaking the gels at 4 degrees C, at which the hydrogel film was swollen. The loaded drug was released gradually in PBS at 37 degrees C, where the hydrogel film was shrunken. Because the hydrogel is biodegradable, the loaded drug could be released completely. It is confirmed that proteins can, in their native structures, be included in the hydrogel via the present technique, as characterized by FTIR, Raman spectrum, UV/VIS spectrum, and circular dichroism spectrum. The highlight of our approach is avoidance of high temperatures and organic solvents in encapsulation, making it ideal for protein drug delivery systems.

A novel microgel and associated post-fabrication encapsulation technique of proteins.

A novel negatively thermo-sensitive and biodegradable microgel was prepared by combination of macromer synthesis and inverse suspension polymerization. A new post-fabrication encapsulation technique based upon this kind of intelligent microgel was developed. Model proteins (hemoglobin, bovine serum albumin and insulin) were encapsulated into the microgels at 4 degrees C and released in vitro at 37 degrees C. Relatively high loading levels and sustained release profiles demonstrate the feasibility of the encapsulation strategy. Since the encapsulation of proteins was performed at low temperature and after the preparation of microgels, organic solvent and high temperature were completely avoided in drug encapsulation. FTIR, Raman and circular dichroism measurements confirmed that the ordered structure of proteins was not destroyed during encapsulation and after release. Thus, the post-fabrication encapsulation technique in this paper is much unique and beneficial for controlled release of biomacromolecular drugs.