Janus Separator

Electrochemical energy storage devices, e.g., rechargeable batteries, flow batteries, fuel cells, and supercapacitors, have been widely exploited and rapidly propelled for a low-carbon, green, and sustainable society The separator is a crucial component of electrochemical energy storage devices and its unique functionalities are indispensable (38). 

For example, separators for secondary batteries and supercapacitors separate the cathode and anode to prevent shorting, while in flow batteries and fuel cells, an ideal separator should selectively control the mass transportation in the cell. 

But in newly emerging electrochemical energy storage devices with revolutionary conversion electrochemistry, such as lithium-sulfur batteries and lithium-air batteries, separators are supposed to play a crucial role in fuUy demonstrating superior high energy density. 

A Janus separator was proposed because Janus structures can offer asymmetry and realize the emergence of properties inconceivable for homogeneous or S5mnmetric structures (39). The name Janus was derived from the Roman god Janus. 

In this Janus separator, a nanoporous poly(propylene) (PP) membrane serves as an insulating substrate in contact with lithium anode while a layer of cellular graphene framework, which has extraordinary electrical conductivity, abimdant in-plane mesopores, high electrochemically active surface area, and large mesopore volume, adheres to the cathode side to reactivate the shuttiing-back of the lithium polysulfides and to preserve the ion channels (39). A meso-porous material is a material containing pores with diameters between 2 and 50 nm (40). 

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The Janus separator of PP-supported cellular graphene framework separator promises the efficient utilization of sulfur cathode with high capacity and good cycling stability. 

Moreover, the Janus separator, besides modifying electrode materials and electrolyte formulations, essentially opens new opportunities for facilitating the utilization of active materials that are... 

Preparation 2-2 Carbonaceous materials are coated on PP substrates via facile filtration. 18 mg of carbon, a cellular graphene framework fabricated by a modified template chemical vapor deposition method on hy-drothermally synthesized MgO templates and 2.0 mg of a poly(vinylidene fluoride) binder were dispersed in N-methyl-2-pyrrolidone, cf. Figure 2.8, by ultrasonication for 1.0 h. Then, 36.0 ml of the dispersion was filtered through a piece of a commercial PP separator (Celgard 2400) and subsequently dried at room temperature for 24.0 h. The Janus separator was found with carbon loading amount of 0.3 mgcm. ... 

Volatiles and cuticular extracts from both sexes of the currant stem girdler, Janus integer, were analyzed by GC-EAD using antenna ofboth sexes. A female specific compound, (9Z)-octadec-9-en-4-olide 7, was identified as active only on male antennas [33]. Separation by chiral GC has shown that only one enantiomer is produced in females. The synthesis ofboth enantiomers has recently been described [34] and the field testing results are forthcoming. 

Janus Green B (3-dimethylamino-7-[4-dimethylaminoazo]-5-phenylphenazonium chloride (2869-83] M 511.1. Dissolves in H2O to give a bluish violet soln which becomes colourless when made lOM in. NaOH. Dissolve in EtOH to give a blue-violet colour, filter from insoluble material then add dry Et2O whereby the dye separates out leaving a small amount of blue colour in soln. Filter off the solid and dry in vacuum. Store in a dark bottle. 

IL-2 often synergizes with other cytokines (notably IL-12) to induce IFNy production by NK cells and to increase cytotoxicity by NK and LAK cells. The expression of the receptor for this cytokine on NK cells is, however, continuous in character, but only a very small percentage of these cells have receptors of great affinity. The study of differential use of Janus kinase-signal transducer activator of transcription signaling pathways in the stimulation of human NK cells by IL-2, IL-12, and IFNa has demonstrated a differential phosphorylation and consequent differential activation of both separate and overlapping STAT proteins by IL-2, IL-12, and IFNa. This may provide a molecular basis for the similarities and differences in the actions of these cytokines on NK cells. ... 

Figure 5.21 TEM images of poly(w-butyl methacrylate)-grafted MWCNTs with azido groups (MWCNT-Az-PnBMA) (a), MWCNTs grafted with both poly( -butyl methacrylate) and poly(ethylene glycol) brushes (MWNT-PnBMA-PEG) (b, c). (d) Cartoon for the local phase separation and assembly of amphiphilic polymer brushes into Janus polymer structures on CNTs as shown in (c) (marked by arrows), (e) Photograph of MWCNT-PnBMA-PEG dispersed in a mixed solvent of water (upper layer) and chloroform (bottom layer). Reprint with permission from Zhang et al...

The use of acrylic acid not only led to a functionalization of nanoparticles, but also was important as a structure-directing monomer for the formation of nanocapsules. In this case, the hydrophilic groups of the acrylic acid [30] or methacrylic acid [31] resulted in the formation of a nanocapsule structure, instead of Janus-like or even separate nanoparticles. The copolymerization of the functional n-methylol acrylamide with vinyl acetate was found to follow (in batch miniemulsion) the Mayo-Lewis equation, despite huge differences in the solubility of the monomers in the aqueous continuous phase [32]. A functionality of fluori-nated particles could be easily introduced by copolymerizing fluoroalkylacrylates with protonated monomers, such as acrylic acid and methacryloxyethyltrimethyl ammonium chloride [33]. 

Figure 30 shows the possible mesophase orderings that one might expect [99]. Early work [102,103] has focused on the possibility of microphase separation in the form of Janus cylinders [104], i.e., the cylinder splits into two halves, with a planar A-B interface (containing the cylinder axis, taken to be the z-axis henceforth). 

When a phase separation into a Janus cylinder structure occurs, e.g., where the upper half of the cylinder contains the B-rich phase and the lower half the A-rich phase, we have a planar AB interface (Fig. 32a) and the quantity that we wish to record is the vector normally oriented to this interface for any monomer of the backbone. Studying the orientational correlations of this vector will yield the desired information on possible fluctuations of interface orientation (Fig. 32b). Since the AB interface at nonzero temperature is not a sharp dividing surface, but rather has a finite width, a numerical characterization of the local orientation of this interface normal is difficult. Therefore, an essentially equivalent but numerically unambiguous characterization of this Janus cylinder-type ordering has been... 

Fig. 32 (a) Perfect phase separation of side chains in a binary (A, B) copolymer bottle bmsh with alternating grafting sequence ABAB... of side chains along the backbone into a Janus cylinder structure implies formation of an AB-interface phase (shaded) between the A-rich part (bottom) and the B-rich part (top) of the cylindrical brush. The local orientation of the interface can be characterized by a unit vector oriented normal to it (arrows), (b) At nonzero but low temperatures, phase separation will occur locally, but entropy will lead to long wavelength fluctuations of the... 

Janus particles have equal phase-separated domains which can be located either in the core or in the corona (if present), whereas multicomparOnent particles can be generally defined as a colloidal structures which are composed of multiple phase-separated domains in the core. Particles with patches on the surface are called patchy particles and have potential applications in electronics and targeted drug delivery. Furthermore, Janus or multicompartment particles with patches on the surface can be called patchy-Janus particles or patchy-multicompartment particles, respectively. 

A special case of a miktoarm star copolymer with many arms are so-called Janus Micelles, which are formed by cross-linking the short middle block of a triblock terpolymer in the microphase separated bulk state, in which the center block self-assembles in spherical [ 189,190] or cylindrical domains [191]. By this procedure the two different outer blocks are oriented to the two opposite hemicoronas around the center block domain and subsequent dissolution leads to amphiphilic particles (Figure 14). While spherical Janus Micelles form superstructures in solution, the cylindrically shaped Janus Micelles seem to have a lower tendency of self-aggregation to higher superstructures. 

It has been reported that a series of polymer blends in aqueous solution could self-assemble into phase-separated structures such as core—shell or Janus-type polymer nanoparticles (Motoyoshi et al, 2010). Moreover, Guo et al (2013) performed DPD simulations to systematically investigate the effects of hydrophobicity and compatibhity, and both play important roles in controlling the self-assembled structures of polymer blends in aqueous solution. Most importantly, the temperature-dependent core-shell to Janus structure transition of thermosensitive polymer blends was observed by DPD simulations for the first time. 

Guo HY, Qiu XQ, Zhou J SelTassembled core-shell and Janus microphase separated structures of polymer blends in aqueous solution, J Chem Phys 139 084907, 2013. 

Cationic dyes acridine orange, crystal violet, Janus green B, methyl violet, neutral red, Pyronin B, Pyronin Y (G), Safranin, Victoria blue B, and Victoria blue 4R, commonly used in histology, were studied by TLC on the Marshall and Lewis system (115). Marshall also separated some Sudan dyes, used for the histological staining of fats, on silica gel TLC sheets using benzene-CHCl3 (10 1) as the mobile phase (115). 

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