Improving the thermal stability of poly[methyl(trifluoropropyl)siloxane] by introducing diphenylsiloxane units.

A series of poly(methyl(trifluoropropyl)-diphenyl siloxane) (P(MTFPS-co-DPS)) was synthesized by polycondensation of diphenylsilanediol and methyltrifluoropropylsiloxanediol. Their chemical structures were investigated by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimeter (DSC). The effect of diphenylsiloxane (DPS) units on the thermal stability of poly[methyl(trifluoropropyl)siloxane] (PMTFPS) was studied by thermogravimetric analysis (TGA), isothermal degradation tests, and pyrolysis-gas chromatography-mass spectrometry (Py-GCMS). The results showed that the thermal stability of PMTFPS improved with the introduction of DPS units into the chain. In particular, the temperature for 5% mass loss in PMTFPS increased by 72 °C under a nitrogen atmosphere. In addition, the mechanism by which the DPS units improve the thermal stability of PMTFPS was also investigated.

Programmable Morphology Evolution of Rod-Coil-Rod Block Copolymer Assemblies Induced by Variation of Chain Ordering.

Morphology transition of block copolymer assemblies in response to external stimuli has attracted considerable attention. However, our knowledge about the mechanism of such a transition is still limited, especially for rod-coil block copolymers. Here, we report a programmable morphology evolution of assemblies induced by variation of chain ordering for rod-coil-rod triblock copolymers. A sequence of morphology transition from ellipsoids to disks, bowls, and vesicles is observed by increasing the solution temperature. At high temperatures, the mobility of the rod chain increases and the rigidity of the rod chain decreases. This gives rise to an ellipsoid-to-vesicle morphology transition. Dissipative particle dynamics theoretical simulations were performed to reveal the mechanism of this morphology transition process. It was found that the increase of rod chain mobility and the decrease of rod chain rigidity induce a decrease of chain ordering of rod blocks as temperature increases, which results in an ellipsoid-to-vesicle morphology transition. The gained information can guide the construction of nanoassemblies based on the rod-coil block copolymers.

High-Safety and Long-Life Silicon-Based Lithium-Ion Batteries via a Multifunctional Binder.

Lithium-ion batteries with high energy density and good safety are in urgent demand nowadays. Silicon has the advantages of high theoretical capacity, low cost, and vast reserves. It is regarded as an ideal anode material for high-energy lithium-ion batteries. Unfortunately, its huge volume change during cycling results in unstable cycle behavior and limits its application. To develop a robust electrode by employing effective binders is still a big challenge. Furthermore, both conventional binders and organic liquid electrolytes bring serious safety risks due to their flammability. Herein, a flame-retardant binder is designed and prepared by cross-linking polyacrylic acid (PAA) with a flame-retardant epoxy resin (FREP) containing phosphorus and nitrogen elements. Compared with PAA, it has better wettability to liquid electrolytes. Moreover, the three-dimensional PAA-FREP polymer binder not only provides sufficient mechanical strength to buffer the volume change of Si powders but also enhances the interfacial adhesion between the active film and Cu current collector via epoxy groups. Most importantly, the FREP component in the binder leads to admirable flame retardance. In these ways, the multifunctional binder exhibits excellent mechanical, electrochemical, and safety performances.

Tuning the thermoreversible temperature domain of PTMC-based networks with thermosensitive links concentration.

In this work, thermoreversible poly(trimethylene carbonate) (PTMC) based networks with different crosslinking densities were obtained by Diels-Alder (DA) reaction between furan-functionalized PTMC precursors and a bismaleimide. Furan-grafted PTMC with various functionalities determined by 1H-NMR analyses were prepared from telechelic PTMC oligomer, glycerol, 4,4'-methylenebis(cyclohexyl isocyanate) (H12MDI) and furfuryl alcohol. The formation of network structures by DA reaction between furan and maleimide groups were proved by Fourier-transform infrared spectroscopy (FT-IR). Although both exo and endo DA adduct forms exist, the thermally more stable exo form dominates. The thermoreversibility of networks was evidenced by FT-IR, solubility, differential scanning calorimetry (DSC) and rheology experiments at different temperatures. By increasing furan functionality or node concentration, denser and stiffer networks could be formed with higher Young's modulus and true stress at break in tensile tests, as well as higher crossover temperature, which indicates a nominal transition from elastic behavior to viscous state. The disruption of networks was found to occur in high temperature ranges from 130 to 160 °C, depending on their crosslinking density.

Production of High Internal Phase Emulsion with a Miniature Twin Screw Extruder.

Emulsions are traditionally prepared by batched emulsifying an oil phase and aqueous phase with a magnetic/mechanical stirrer, homogenizer, or ultrasonic machine, etc. Herein, high internal phase emulsions (HIPEs) produced with a miniature twin screw extruder were first investigated. Adding an oil phase (the mixture of styrene, divinylbenzene, and span 80) and aqueous phase to the inlet of a miniature twin screw extruder, a series of white and viscous HIPEs were obtained at the outlet of the extruder. With the screw rotation speed and the surfactant content varied respectively in the ranges of 50-200 rpm and 5-20%, a series of HIPEs having uniform droplet size were produced. Polymerizing these HIPEs caused a series of polymerized HIPES, which have a well-defined open-cell structure. The method developed herein shows that it is possible to prepare emulsions with oil and water by twin screw extrusion. Also, it may also cause a continuous preparation of HIPEs when the miniature twin screw extruder was replaced by an industrial extruder.

A controlled synthesis method of alkyl methacrylate block copolymers via living anionic polymerization at ambient temperature.

A controlled synthesis method of alkyl methacrylate block copolymers such as poly(methyl methacrylate)-b-poly(ethyl methacrylate) (PMMA-b-PEMA), poly(methyl methacrylate)-b-poly(butyl methacrylate) (PMMA-b-PBMA) and poly(ethyl methacrylate)-b-poly(butyl methacrylate) (PEMA-b-PBMA) via living anionic polymerization was innovated with potassium tert-butoxide (t-BuOK) as initiator in tetrahydrofuran(THF) solvent. The sequential anionic copolymerization could be smoothly conducted at 0 °C and the conversion of all monomers reached up to almost 100%. The copolymers were characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H-NMR), fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analysis (DMA). It was found that all block copolymers were in a narrow MWD while M w and weight ratio of each block were coincided with the theoretical values and feed ratio. DMA measurement indicated that all the block copolymers have two glass transition temperatures which have proved the certain microphase separation and the partial compatibility of the blocks. The similar results were achieved after changing feed order or addition amount. Furthermore, the reactivity ratio was also studied and confirmed that reactivity ratio of MMA was the largest among alkyl methacrylate. Based on these results, the anionic block copolymerization containing polar alkyl methacrylate monomers at a commercial scale starts to become possible.

Synthesis of Emulsion-Templated Magnetic Porous Hydrogel Beads and Their Application for Catalyst of Fenton Reaction.

The pristine Fe3O4 nanoparticle (FeNP) is supposed to be a good catalyst of Fenton processes which have shown significant potential for water purification. Herein the magnetic macroporous hydrogel beads, having an open-cell structure, were synthesized by sedimentation polymerization of pristine FeNP stabilized oil-in-water high internal phase emulsions. The effects of the FeNP amount, internal phase fraction, and the costabilizer Tween85 concentration on the structure, such as interconnecting degree, void size, and its distribution of both the surface and inner of the beads, were investigated. With a methyl orange (MO) aqueous solution passing through a chromatography column that was filled with the FeNPs loaded hydrogel beads, the efficiency of these hydrogel beads as catalyst for Fenton reaction to decompose MO in water was tested. The MO was decomposed quickly at the first hour, followed by decomposed gradually in a further 5 h, and the decomposition rate of MO could be up to 99.6% at the end of the test. Moreover, MO decomposition rate remained over 98.2% in six batches which were run in the same beads filled column. The results showed that these FeNPs loaded porous hydrogel beads were reusable and highly efficient supporter for catalysis of Fenton reaction for decomposing organic pollutants in water.

Macroporous polymers prepared via frozen UV polymerization of the emulsion-templates stabilized by a low amount of surfactant.

Macroporous polymers based on high internal phase emulsions (HIPEs) possess tunable porous structures and device shapes, and these characteristics make it possible for it to be applied in many fields. However, such materials also demonstrate undesirable properties, such as their brittleness and chalkiness, due to a great amount of surfactant required (5.0-50.0%, relative to the external phase) to realize the transformation from HIPEs to macroporous polymers (polyHIPEs). Herein, O/W HIPEs stabilized by a small amount (as low as 0.1 wt%, relative to the external phase) of commercial surfactant were prepared by magnetic stirring and subsequently homogenizing, and well-defined polyHIPEs were obtained through frozen UV polymerization of these HIPEs. In this process, the prepared HIPE was squeezed out by an injector and frozen at once, which effectively prevented the coalescence of internal phase. Then a 365 nm UV light was utilized to initiate the polymerization and the temperature was kept at -20 °C in order to avoid the melting of the frozen HIPE. After the polymerization, samples, having a typical polyHIPE structure, were obtained. Besides, the original monomer, surfactant and the oil (internal phase) were respectively replaced, and well-defined polyHIPEs could still be obtained. All the results suggested that frozen UV polymerization of HIPEs was an effective and universal approach to produce polyHIPEs with a low amount of surfactant.

Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2.

Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms·pm²), the maximum Stark splitting manifold of ²F7/2 level (781 cm-1), and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers.

Tuning of the surface biological behavior of poly(L-lactide)-based composites by the incorporation of polyelectrolyte complexes for bone regeneration.

Poly(L-lactide)(PLLA)-based composites have been widely used for tissue regeneration. Novel polyelectrolyte complexes (PECs) consisted of carboxymethyl starch sodium (CMS) and chitosan oligosaccharide (COS) was fabricated and evaluated. The results suggested that the CMS/COS-PECs (CC-PECs) distinguished from the original polymers alone, presenting an amorphous structure. Then, the CC-PECs/PLLA composites were prepared by varying the relative amount of CC-PECs in the PLLA-matrix, demonstrated by means of the surface morphology, hydrophilicity, water uptake, in vitro degradability and primary cell responses. The results suggested that the CC-PECs physically attached on the PLLA surface enhanced the formation of the surface seepage network, which could target modification of the surface biological behavior of the materials. The phenomena had been evidenced by the performed tests in respect to hydrophilicity, water uptake and degradation in PBS, which also may provide effective support for cell adhesion and proliferation. Further, the CC-PECs/PLLA surfaces clearly promoted the adhesion and proliferation of MC3T3-E1 cells compared with PLLA materials, indicating excellent cytocompatibility. This study suggested that the CC-PECs/PLLA-50 composite with excellent biological behavior could be a promising candidate for bone repair.

Macroporous Polymers with Aligned Microporous Walls from Pickering High Internal Phase Emulsions.

A novel class of macroporous polymers, open macroporous polymers with aligned microporous void walls, were prepared by combining particle-stabilized high internal phase emulsion (Pickering HIPE) and unidirectional freezing technique. These Pickering HIPEs were prepared by utilizing poly(urethane urea)/(vinyl ester resin) nanoparticles as the sole stabilizer, and this nanoparticles also acted as building blocks for the resulting macroporous polymers. Moreover, the morphology and compression modulus of the resulting porous materials could be tuned easily. This means now Pickering-HIPE templated open-cell foams can be prepared, and this route was normally achieved with surfactant and/or chemical reaction involved.

Nitrogen-doped hierarchical porous carbon microsphere through KOH activation for supercapacitors.

A porous carbon microsphere with moderate specific surface area and superior specific capacitance for supercapacitors is fabricated from polyphosphazene microsphere as the single heteroatoms source by the carbonization and subsequent KOH activation under N2 atmosphere. With KOH activation, X-ray photoelectron spectroscopy analysis confirms that the phosphorus of polyphosphazene microsphere totally vanishes, and the doping content of nitrogen and its population of various functionalities on porous carbon microsphere surface are tuned. Compared with non-porous carbon microsphere, the texture property of the resultant porous carbon microsphere subjected to KOH activation has been remarkably developed with the specific surface area growing from 315 to 1341 m(2) g(-1)and the pore volume turning from 0.17 to 0.69 cm(3) g(-1). Prepared with the KOH/non-porous carbon microsphere weight ratio at 1.0, the porous carbon microsphere with moderate specific surface area of 568 m(2) g(-1), exhibits intriguing electrochemical behavior in 1 M H2SO4 aqueous electrolyte, with superior specific capacitance (278 F g(-1) at 0.1 A g(-1)), good rate capability (147 F g(-1) remained at 10 A g(-1)) and robust cycling durability (No capacitance loss after 5000 cycles). The promising electrochemical performance could be ascribed to the synergy of nitrogen heteroatom functionalities and the porous morphology.

Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions.

Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, the Co/N-C composite also shows better bifunctional catalytic activity than its oxidative counterparts, which could be attributed to the high specific surface area and the efficient charge transfer ability of the composite, as well as the good synergistic effect between N-doped carbon and the Co nanoparticles in the Co/N-C composite.

Development and population study of the 12 X-STR loci multiplexes PCR systems.

To develop a multiplex polymerase chain reaction (PCR) system with 12 X-chromosomal short-tandem repeat (X-STR) loci and to investigate their polymorphism and linkage and/or independence, the 12 loci (DXS6807, DXS8378, DXS9902, DXS6800, DXS6803, DXS6799, DXS6804, GATA172D05, DXS6854, HPRTB, DXS8377, and DXS7423) were simultaneously analyzed in 1,005 unrelated individuals (574 males and 431 females) from Guangdong Han individuals and Kazakh populations living in China. The allele frequencies and mutation rates were investigated. Allele frequency distribution among different populations was compared. Haplotypes of linkage disequilibrium markers (DXS6807-DXS8378-DXS9902) and linked markers (DXS6804-GATA172D05 and DXS8377-DXS7423) were also reported. A total of 117 alleles, ranging from five to 20 for each locus, were observed in our selected populations. Eight cases with mutation of the selected loci were detected in 9,480 meioses. Pairwise comparisons of allele frequencies distribution showed statistically significant differences at most loci among different populations. Haplotype diversity of linked markers was 0.9404-0.9694. The results indicated that this multiplex system is very useful for forensic analysis and may be complementarities for X-12 kits or X-8 kits in forensic case.

PMMA based foams made via surfactant-free high internal phase emulsion templates.

Open porous PMMA based foams have been synthesized from surfactant-free high internal phase emulsion templates.

[Analysis on the injury by lock-against-theft].

Nowdays, it is common seen that criminals tend to use the lock-against-theft for motorcycle to harm others as a tool. In order to find out the chief characters of this kind of injury, 28 cases in which victims were hurt by lock-against-theft for motorcycle were analyzed. In each case, the victims carefully questioned to confirm the damage procedure. Furthermore, the wound configuration was observed and the forming mechanism was deduced to provide morphological evidences for the judgement in this kind of case.