A Novel Dynamic Polymer Synthesis via Chlorinated Solvent Quenched Depolymerization

Dynamic polymers with both physical interactions and dynamic covalent bonds exhibit superior performance,but achieving such dry polymers in an effi-cient manner remains a challenge.Herein,we report a novel organic solvent quenched polymer synthesis using the natural molecule thioctic acid(TA),which has both a dynamic disulfide bond and carboxylic acid.The effects of the solvent type and concentration along with reaction times on the proposed reaction were thoroughly explored for polymer synthesis.Solid-state proton nuclear magnetic resonance(1 H NMR)and first-principles simulations were carried out to investigate the reaction mechanism.They show that the chlorinated solvent can efficiently stabilize and mediate the depolymerization of poly(TA),which is more kinetically favorable upon lowering the temperature.Attributed to the numerous dynamic covalent disulfide bonds and noncovalent hydrogen bonds,the obtained poly(TA)shows high extensibility,self-healing,and reprocessable properties.It can also be employed as an efficient adhesive even on a Teflon surface and 3D printed using the fused deposition modeling technique.This new polymer synthesis approach of using organic solvents as catalysts along with the unique reaction mechanism provides a new pathway for efficient polymer synthesis,especially for multifunctional dynamic polymers.

High-Performance 3-D Fiber Network Composite Electrolyte Enabled with Li-Ion Conducting Nanofibers and Amorphous PEO-Based Cross-Linked Polymer for Ambient All-Solid-State Lithium-Metal Batteries

Solid electrolytes have gained attention recently for the development of next-generation Li-ion batteries since they can fun-damentally improve the battery stability and safety.Among various types of solid electrolytes,composite solid electrolytes(CSEs)exhibit both high ionic conductivity and excellent interfacial contact with the electrodes.Incorporating active nanofib-ers into the polymer matrix demonstrates an effective method to fabricate CSEs.However,current CSEs based on traditional poly(ethylene oxide)(PEO)polymer suffer from the poor ionic conductivity of PEO and agglomeration effect of inorganic fillers at high concentrations,which limit further improvements in Li+conductivity and electrochemical stability.Herein,we synthesize a novel PEO based cross-linked polymer(CLP)as the polymer matrix with naturally amorphous structure and high room-temperature ionic conductivity of 2.40×10^(−4)S cm^(−1).Li_(0.3)La_(0.557)TiO_(3)(LLTO)nanofibers are incorporated into the CLP matrix to form composite solid electrolytes,achieving enhanced ionic conductivity without showing filler agglomeration.The high content of Li-conductive nanofibers improves the mechanical strength,ensures the conductive network,and increases the total Li+conductivity to 3.31×10^(−4)S cm^(−1).The all-solid-state Li|LiFePO_(4)batteries with LLTO nanofiber-incorporated CSEs are able to deliver attractive specific capacity of 147 mAh g^(−1)at room temperature,and no evident dendrite is found at the anode/electrolyte interface after 100 cycles.

Multifunctional Fibroblasts Enhanced via Thermal and Freeze-Drying Post-treatments of Aligned Electrospun Nanofiber Membranes

Parallel fibrous scaffolds play a critical role in controlling the morphology of cells to be more natural and biologically inspired.Among popular tissue engineering materials,poly(2-hydroxyethyl methacrylate)(pHEMA)has been widely investigated in conventional forms due to its biocompatibility,low toxicity,and hydrophilicity.However,the swelling of pHEMA in water remains a major concern.To address this issue,randomly oriented and aligned as-spun pHEMA nanofibrous scaffolds were first fabricated at speeds of 300 and 2000 rpm in this study,which were then post-treated using either a thermal or a freeze-drying method.In cell assays,human dermal fibroblasts(HDFs)adhered to the freeze-drying treated substrates at a significantly faster rate,whereas they had a higher cell growth rate on thermally-treated substrates.Results indicated that the structural properties of pHEMA nanofibrous scaffolds and subsequent cellular behaviors were largely dependent on post-treatment methods.Moreover,this study suggests that aligned pHEMA nanofibrous substrates tended to induce regular fibroblast orientation and unidirectionally oriented actin cytoskeletons over random pHEMA nanofibrous substrates.Such information has predictive power and provides insights into promising post-treatment methods for improving the properties of aligned pHEMA scaffolds for numerous tissue engineering applications.

A hybrid lithium sulfonated polyoxadiazole derived single-ion conducting gel polymer electrolyte enabled effective suppression of dendritic lithium growth

Lithium metal is deemed as an ideal anode material in lithium-ion batteries because of its ultrahigh theoretical specific capacity and the lowest redox potential.However,the rapid capacity attenuation and inferior security resulting from the dendritic lithium growth severely limit its commercialization.Herein a novel hybrid gel polymer electrolyte (GPE) based on electrospun lithium sulfonated polyoxadiazole (LiSPOD) nanofibrous membrane swelled by lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) ether liquid electrolyte is proposed to address the issue of lithium dendrites.The Li-SPOD membrane synthesized by a simple one-pot method exhibits excellent mechanical strength and thermal resistance due to its high molecular weight and rigid backbone.The electron-withdrawing oxadiazole ring and oxadiazole ring-Li;complex,and N,O heteroatoms with lone pairs of electrons in Li-SPOD macromolecular chains facilitate the dissociation of-SO_(3)Li group and Li^(+)transference.The hybrid Li-SPOD GPE exhibits both a high lithium-ion transference number (0.64) and high ionic conductivity (2.03 m S/cm) as well as superior interfacial compacity with lithium anodes.The Li Fe PO_(4)-Li cell using this novel GPE can operate steadily at 2C for 300 cycles,remaining a high discharge capacity of 125 m Ah/g and dendrite-free anode.Remarkable performance improvements for the Li-Li and Cu-Li cells are also presented.

Ionic/electronic conductivity regulation of n-type polyoxadiazole lithium sulfonate conductive polymer binders for high-performance silicon microparticle anodes

Low-cost silicon microparticles(SiMP),as a substitute for nanostructured silicon,easily suffer from cracks and fractured during the electrochemical cycle.A novel n-type conductive polymer binder with excellent electronic and ionic conductivities as well as good adhesion,has been successfully designed and applied for high-performance SiMP anodes in lithium-ion batteries to address this problem.Its unique features are attributed to the stro ng electron-withdrawing oxadiazole ring structure with sulfonate polar groups.The combination of rigid and flexible components in the polymer ensures its good mechanical strength and ductility,which is beneficial to suppress the expansion and contraction of SiMP s during the charge/discharge process.By fine-tuning the monomer ratio,the conjugation and sulfonation degrees of the polymer can be precisely controlled to regulate its ionic and electronic conductivities,which has been systematically analyzed with the help of an electrochemical test method,filling in the gap on the conductivity measurement of the polymer in the doping state.The experimental results indicate that the cell with the developed n-type polymer binder and SiMP(~0.5 μm) anodes achieves much better cycling performance than traditional non-conductive binders.It has been considered that the initial capacity of the SiMP anode is controlled by the synergetic effect of ionic and electronic conductivity of the binder,and the capacity retention mainly depends on its electronic conductivity when the ionic conductivity is sufficient.It is worth noting that the fundamental research of this wo rk is also applicable to other battery systems using conductive polymers in order to achieve high energy density,broadening their practical applications.

Electrospun Nanofibers Enabled Advanced Lithium−Sulfur Batteries

CONSPECTUS:Lithium−sulfur(Li−S)batteries have been extensively studied because both S and Li have high theoretical capacities,and S is abundant and environmentally friendly.However,their practical applications have been hindered by several challenges,including poor conductivity of S and its intermediates,shuttle effects of polysulfides,Li dendrite growth,etc.Tremendous efforts have been taken to tackle these issues by developing functional S host materials,separators and interlayers,solid-state electrolytes,etc.,during the past decade.Compared to structurally complicated materials and intricate preparation approaches,electrospun nanofibers have obtained tremendous interests since they have played an extremely crucial role in improving the overall performance of Li−S cells due to their unique features such as easy-setup,substantial surface area,outstanding flexibility,high porosity,excellent mechanical properties,etc.