BSA adsorption on bimodal PEO brushes

BSA adsorption onto bimodal PEO brushes at a solid surface was measured using optical reflectometry. Bimodal brushes consist of long (N=770) and short (N=48) PEO chains and were prepared on PS surfaces, applying mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) block copolymers and using the Langmuir-Blodgett technique. Pi-A isotherms of (mixtures of) the block copolymers were measured to establish the brush regime. The isotherms of PS(29)-PEO(48) show hysteresis between compression and expansion cycles, indicating aggregation of the PS(29)-PEO(48) upon compression. Mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) demonstrate a similar hysteresis effect, which eventually vanishes when the ratio of PS(37)-PEO(770) to PS(29)-PEO(48) is increased. The adsorption of BSA was determined at brushes for which the grafting density of the long PEO chains was varied, while the total grafting density was kept constant. BSA adsorption onto monomodal PEO(48) and PEO(770) brushes was determined for comparison. The BSA adsorption behavior of the bimodal brushes is similar to the adsorption of BSA at PEO(770) monomodal brushes. The maximum of BSA adsorption at low grafting density of PEO(770) can be explained by ternary adsorption, implying an attraction between BSA and PEO. The contribution of primary adsorption to the total adsorbed amount is negligible.     

聚合物-锂改性蒙脱石复合材料离子迁移

以聚合物（ＰＥＯ,ＰＥＯ－ＰＭＭＡ）和锂改性蒙脱石作为主要原料,采用聚合物粉末直接熔融嵌入的方法,制备聚合物－蒙脱石复合材料．利用ＮＭＲ、ＡＣ阻抗等分析方法探讨了复合材料中聚合物链对 Ｌｉ＋离子迁移的影响．结果表明,聚合物（ＰＥＯ）嵌入蒙脱石层间,层间聚合物链的无序度增大,有利于Ｌｉ＋离子迁移．ＰＭＭＡ引入对ＰＥＯ链的改性,进一步加大聚合物链的无序度,更易于层间Ｌｉ＋离子迁移;复合材料的常温离子电导率接近１０－２Ｓ·ｃｍ－１,且具有良好的温度稳定性．     

Advances in host selection and interface regulation of polymer electrolytes

Polymer electrolyte (PE) has been emerging as a promising alternative to liquid electrolytes due to the unique advantages such as excellent flexibility and processability, high chemical and thermal stability, and low risk of leakage and combustion, especially for lithium-ion batteries (LIBs). Even though abundant attempts focusing on polymer chemistries have been made, the inadequate capacity of lithium-ion transport via segmental motion still cannot provide satisfying room temperature ionic conductivity and lithium-ion transference number. In addition, safety concerns and short lifespan resulted from the brittle and incompatible interface between the electrode and polymer materials also hinder the commercialization of PEs-based LIBs. Hence, for the above performance defects and interface issues, this review provides an overview of polymer electrolytes from the conductivity improvement, polymer selection and mechanical strength enhancement for protrusion suppressing. The improvement of conductivity specifically includes structure modification of poly(ethylene oxide) (PEO) host and novel electrolyte matrix beyond PEO, while the section of interface regulation mainly involves dendrite-inhibited polymers, mechanical strengthening, and in situ polymerization. Finally, perspectives and challenges are pointed out in the development of polymer electrolytes with both excellent electrochemical performance and safety for LIBs.     

Electrokinetic characterization of poly(acrylic acid) and poly(ethylene oxide) brushes in aqueous electrolyte solutions

Surfaces carrying hydrophilic polymer brushes were prepared from poly(styrene)-poly(acrylic acid) and poly(styrene)-poly(ethylene oxide) diblock copolymers, respectively, using a Langmuir-Blodgett technique and employing poly(styrene)-coated planar glass as substrates. The electrical properties of these surfaces in aqueous electrolyte were analyzed as a function of pH and KCl concentration using streaming potential/streaming current measurements. From these data, both the zeta potential and the surface conductivity could be obtained. The poly(acrylic acid) brushes are charged due to the dissociation of carboxylic acid groups and give theoretical surface potentials of -160 mV at full dissociation in 10(-)(3) M solutions. The surface conductivity of these brushes is enormous under these conditions, accounting for more than 93% of the total measured surface conductivity. However, the mobility of the ions within the brush was estimated from the density of the carboxylic acid groups and the surface conductivity data to be only about 14% of that of free ions. The poly(ethylene oxide) (PEO) brushes effectively screen the charge of the underlying substrate, giving a very low zeta potential except when the ionic strength is very low. From the data, a hydrodynamic layer thickness of the PEO brushes could be estimated which is in good agreement with independent experiments (neutron reflectivity) and theoretical estimates. The surface conductivity in this system was slightly lower than that of the polystyren substrate. This also indicates that no significant amount of preferentially, i.e., nonelectrostatically attracted, ions taken up in the brush.     

Enhanced ionic conductivity in PEO/PMMA glassy miscible blends: Role of nano‐confinement of minority component chains

AC impedance spectroscopy was used to investigate the ionic conductivity of solution cast poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends doped with lithium perchlorate. At low PEO contents (below overlap weight fraction w^*), ionic conductivities are almost low. This could be due to nearly distant PEO chains in blend, which means ion transportation cannot be performed adequately. However, at weight fractions well above w^*, a significant increase in ionic conductivity was observed. This enhanced ionic conductivity mimics the PEO segmental relaxation in rigid PMMA matrix, which can be attributed to the accelerated motions of confined PEO chains in PMMA matrix. At PEO content higher than 20 wt % the conductivity measured at room temperature drops due to crystallization of PEO. However by increasing temperature to temperatures well above the melting point of PEO, a sudden increase of conductivity was observed which was attributed to phase transition from crystalline to amorphous state. The results indicate that some PEO/PMMA blends with well enough PEO content, which are structurally solid, can be considered as an interesting candidate for usage as solid‐state electrolytes in Lithium batteries. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2065–2071, 2010     

Gold nanoparticle/polymer nanocomposites: dispersion of nanoparticles as a function of capping agent molecular weight and grafting density

The dispersion of polymer-covered gold nanoparticles in high molecular weight (MW) polymer matrixes is reported. Complete particle dispersion was achieved for PS125-Au in the polystyrene (PS) matrixes studied (up to and including Mn = 80 000 g/mol). PS19-Au, on the other hand, exhibits complete dispersion in a low MW PS matrix (Mn = 2000 g/mol) but only partial dispersion in higher MW matrixes (up to 80 000 g/mol). Similarly, PEO45-Au is fully dispersed in a low MW poly(ethylene oxide) (PEO) matrix (Mn = 1000 g/mol) but only partially in a higher MW PEO matrix (Mn = 15 000 g/mol). Wetting of the polymer-Au brushes by the polymer matrix is associated with dispersibility. Theory predicts that, for dense polymer brushes, wetting is achieved when the MW of the polymer brush equals (and is greater than) that of the polymer matrix. The observed partial dispersion of the PS19-Au and PEO45-Au nanoparticles in matrixes whose MW is greater than the brush MW is attributable to the existence of a high volume fraction of voids within the brush. These voids arise from the unique geometry of the nanoparticle surface arising from the juxtaposed facets of the gold nanoparticle. PS125-Au brushes are wetted by PS matrixes whose degree of polymerization is larger than 125, probably because of their lower grafting density on the gold core or the high fraction of void volumes caused by the facets on the gold cores. Dispersion thus occurs when the matrix MW is greater than that of the brush.     

PEO/LiClO_4纳米SiO_2复合聚合物电解质的电化学研究

将实验室制备的纳米二氧化硅和市售纳米二氧化硅粉末与PEO LiClO4复合 ,制得了复合PEO电解质 .它们的室温离子电导率可比未复合的PEO电解质提高 1～ 2个数量级 ,最高可以达到 1 2 4× 10 - 5S cm .离子电导率的提高有两方面的原因 :一是无机二氧化硅粉末的加入抑制了PEO的结晶 ,是二氧化硅粉末和聚合物电解质之间形成的界面对电导率的提高也有一定的作用 .在进一步加入PC EC(碳酸丙烯酯 碳酸乙烯酯 )混合增塑剂后制得的复合凝胶PEO电解质 ,可使室温离子电导率再提高 2个数量 ,达到 2× 10 - 3 S cm .用这种复合凝胶PEO电解质组装了Li|compositegelelectrolyte|Li半电池 ,并测量了该半电池的交流阻抗谱图随组装后保持时间的变化 ,实验观察到在保持时间为 144h以内钝化膜的交流阻抗迅速增大 ,但在随后的时间内逐渐趋于平稳 ,表明二氧化硅粉末的加入可以有效地抑制钝化膜的生长     

Ultraviolet-Cured Semi-Interpenetrating Network Polymer Electrolytes for High-Performance Quasi-Solid-State Lithium Metal Batteries

Solid polymer electrolytes with relatively low ionic conductivity at room temperature and poor mechanical strength greatly restrict their practical applications. Herein, we design semi-interpenetrating network polymer (SNP) electrolyte composed of an ultraviolet-crosslinked polymer network (ethoxylated trimethylolpropane triacrylate), linear polymer chains (polyvinylidene fluoride-co-hexafluoropropylene) and lithium salt solution to satisfy the demand of high ionic conductivity, good mechanical flexibility, and electrochemical stability for lithium metal batteries. The semi-interpenetrating network has a pivotal effect in improving chain relaxation, facilitating the local segmental motion of polymer chains and reducing the polymer crystallinity. Thanks to these advantages, the SNP electrolyte shows a high ionic conductivity (1.12 mS cm⁻¹ at 30 °C), wide electrochemical stability window (4.6 V vs. Li⁺/Li), good bendability and shape versatility. The promoted ion transport combined with suppressed impedance growth during cycling contribute to good cell performance. The assembled quasi-solid-state lithium metal batteries (LiFePO₄/SNP/Li) exhibit good cycling stability and rate capability at room temperature.     

Synthesis of networked polymers with lithium counter cations from a difunctional epoxide containing poly(ethylene glycol) and an epoxide monomer carrying a lithium sulfonate salt moiety

Poly(ethylene glycol)‐based networked polymers that had lithium sulfonate salt structures on the network were prepared by heating a mixture of poly(ethylene glycol) diglycidyl ether (PEGGE), poly(ethylene glycol) bis(3‐aminopropyl) terminated (PEGBA), and an ionic epoxy monomer, lithium 3‐glycidyloxypropanesulfonate (LiGPS). Flexible self‐standing networked polymer films showed high thermal stability, low crystallinity, low glass transition temperature, and good mechanical strength. The materials were ion conductive at room temperature even under a dry condition, although the ionic conductivity was rather low (10^?6 to 10^?5 S/m). The ionic conductivity increased with the increase in temperature to above 1 × 10^?4 S/m at 90 °C. The film samples became swollen by immersing in propylene carbonate (PC) or PC solution of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The samples swollen in PC showed higher ionic conductivity (ca.1 × 10^?3 S/m at room temperature), and the samples swollen in LiTFSI/PC showed much higher ionic conductivity (nearly 1 S/m at room temperature). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3113–3118, 2010     

Interface interaction within nanopores in thin films of an amphiphilic block copolymer and CTAB

Anion exchange membranes with semi-interpenetrating polymer network (semi-IPN) were prepared based on quaternized chitosan (QCS) and polystyrene (PS). The PS was synthesized by polymerization of styrene monomers in the emulsion of the QCS in an acetic acid aqueous solution under nitrogen atmosphere at elevated temperatures. The semi-IPN system was formed by post-cross-linking of the QCS. A hydroxyl ionic conductivity of 2.80×10(-2) S cm(-1) at 80°C and a tensile stress at break of 20.0 MPa at room temperature were reached, respectively, by the semi-IPN membrane containing 21 wt.% of the PS. The durability of the semi-IPN membrane in alkaline solutions was tested by monitoring the variation of the conductivity and the mechanical strength. The degradation of the conductivity at 80°C was about 5% by immersing the membrane in a 1 mol L(-1) KOH solution at room temperature for 72 h and at 60°C for 50 h, respectively. The tensile stress at break at room temperature could maintain about 20.0 MPa for the membrane soaking in a 10 mol L(-1) KOH solution at ambient temperature for more than 70 h. The water swelling of the semi-IPN membranes was discussed based on the stress relaxation model of polymer chains, and it obeyed the Schott's second-order swelling kinetics.     

相态结构对聚氧化乙烯/丁二腈/高氯酸锂复合电解质室温电导率的影响

采用聚氧化乙烯(PEO)、丁二腈和高氯酸锂(LiClO4)的复合电解质体系, 制备了一系列不同配比的PEO/SN/LiClO4复合电解质, 对其室温电性能和相态结构进行了表征, 并探讨了相态结构对室温电导率的影响.     

Lithium‐Salt‐Containing High‐Molecular‐Weight Polystyrene‐block‐Polyethylene Oxide Block Copolymer Films

Ionic conductivity in relation to the morphology of lithium‐doped high‐molecular‐weight polystyrene‐block‐polyethylene oxide (PS‐b‐PEO) diblock copolymer films was investigated as solid‐state membranes for lithium‐ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt‐doping level and the temperature. The PEO crystallites completely vanished at a salt‐doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS‐b‐PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded‐like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt‐doping level.     

Polymer electrolytes based on room temperature ionic liquid: 2,3-dimethyl-1-octylimidazolium triflate

Room temperature ionic liquid (DMOImTf) based upon 2,3-dimethyl-1-octylimidazolium cation and trifluoromethanesulfonate or triflate (CF(3)SO(3))(-) anion has been synthesized and shows conductivity of 5.68 mS/cm and viscosity of 26.4 cP at 25 degrees C. Ion conducting polymer electrolytes based on polymers (poly(ethylene oxide) (PEO) and polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP)) and ionic liquid (DMOImTf) were prepared in film form by the casting technique. The conductivity of polymer electrolytes containing 0.5 M LiCF(3)SO(3) in PEO:DMOImTf taken in equal weight ratio increases with the addition of propylene carbonate (PC) while its mechanical stability improved by dispersing nanosize fumed silica. However, polymer electrolytes containing PVdF-HFP and ionic liquid show a high value of conductivity (10(-4)-10(-3) S/cm) alongwith better mechanical stability.     

Safety-enhanced Polymer Electrolytes with High Ambient-temperature Lithium-ion Conductivity Based on ABA Triblock Copolymers

Liquid electrolytes used in lithium-ion batteries suffer from leakage,flammability,and lithium dendrites,making polymer electrolyte a potential alternative.Herein,a series of ABA triblock copolymers(ABA-x)containing a mesogen-jacketed liquid crystalline polymer(MJLCP)with a polynorbornene backbone as segment A and a second polynorbornene-based polymer having poly(ethylene oxide)(PEO)side chains as segment B were synthesized through tandem ring-opening metathesis polymerizations.The block copolymers can self-assemble into ordered morphologies at 200℃.After doping of lithium salts and ionic liquid(IL),ABA-x self-assembles into cylindrical structures.The MJLCP segments with a high glass transition temperature and a stable liquid crystalline phase serve as physical crosslinking points,which significantly improve the mechanical performance of the polymer electrolytes.The ionic conductivity of ABA-x/lithium salt/IL is as high as 10-3 S·cm-1 at ambient temperature owing to the high IL uptake and the continuous phase of conducting PEO domains.The relationship between ionic conductivity and temperature fits the Vogel-Tamman-Fulcher(VTF)equation.In addition,the electrolyte films are flame retardant owing to the addition of IL.The polymer electrolytes with good safety and high ambient-temperature ionic conductivity developed in this work are potentially useful in solid lithium-ion batteries.     

聚苯并咪唑-锂盐-聚乙二醇单甲醚共混全固态聚合物电解质的制备及性能

使用共混后浇铸成膜的方法,制备了聚苯并咪唑-锂盐-聚乙二醇单甲醚组成的锂离子电池共混全固态聚合物电解质。通过傅里叶红外光谱(FT-IR)、X射线衍射(XRD)、差示扫描量热(DSC)、拉伸与交流阻抗测试表征了共混全固态电解质的结构与性能。研究了不同锂盐以及各组分含量对共混全固态电解质的力学性能与电导率的影响。结果表明:聚苯并咪唑与聚乙二醇单甲醚之间存在氢键;共混全固态电解质中聚乙二醇单甲醚处于无定形态;锂盐的加入使聚乙二醇单甲醚的玻璃化转变温度下降;聚乙二醇单甲醚含量越高,共混膜强度越低,电导率越高,并且使用三氟甲磺酸锂作为锂盐时其电导率最高,室温下可以达到3.58×10~(-5) S/cm,高温下可以达到3.3×10~(-3) S/cm,高温下满足对锂离子电池的使用需求。     

Effect of addition of 1-butyl-3-methylimidazolium thiocyanate on conductivity of Na-containing polymer electrolyte

Research in the environmentally friendly energy field has grown rapidly due to severe problems such as global warming and climate change. Sodium-ion technology is one of the most promising alternatives to lithium-ion batteries. Use of ionic liquids containing thiocyanate anion has been considered because of their low cost, low viscosity, and nonhazardous nature. In this work, polyethylene oxide (PEO)–sodium perchlorate (NaClO₄) samples containing different amounts of 1-butyl-3-methylimidazolium thiocyanate ionic liquid were prepared by a solution casting method. Addition of the ionic liquid to the PEO–NaClO₄ electrolyte further increased the ionic conductivity. The electrolyte containing 30 wt% ionic liquid exhibited the maximum ionic conductivity of ~5.0 × 10^?4 S/cm at room temperature. Fourier-transform infrared (FT-IR) spectroscopy revealed the interaction between the polymer chain and salt ion complexes for various sodium salt contents. Differential scanning calorimetry (DSC) demonstrated that the crystallinity was reduced by addition of 1-butyl-3-methylimidazolium thiocyanate ionic liquid.     

聚碳酸酯基固态聚合物电解质的研究进展

液态锂离子电池由于采用易泄露、易挥发、易燃烧的碳酸酯有机溶剂,在高温或极端条件下使用时,存在极大的安全隐患.使用固态电解质替代液态电解液,可以从根本上避免此类安全问题的发生,与此同时还可以大幅度提升固态锂电池的能量密度.固态电解质又分为无机固态电解质和聚合物固态电解质2大类.无机固态电解质能够在宽的温度范围内保持化学稳定性,并且电化学窗口较宽,机械强度更高,室温离子电导率较高,但脆性较大,柔韧性差,制备工艺复杂,成本较高.聚合物固态电解质,室温离子电导率偏低,难以满足室温锂离子电池的应用,但其加工成型容易,形状可变.比较而言,固态聚合物电解质,更适宜大规模生产,离产业化相对更近.固态聚合物电解质中研究较多的是聚醚基固态聚合物电解质(如聚环氧乙烷和聚环氧丙烷),但其缺点是室温离子电导率低,需要对其改性或进一步开发综合性能更加优异的其他固态聚合物电解质.聚碳酸酯基固态聚合物电解质由于其特殊的分子结构(含有强极性碳酸酯基团)以及高介电常数,可以有效减弱阴阳离子间的相互作用,提高载流子数量,从而提高离子电导率,因此被认为是一类非常有前途的固态聚合物电解质体系.基于此,本文重点综述了最近研究热点的聚碳酸酯基固态聚合物电解质,包括聚(三亚甲基碳酸酯)体系、聚(碳酸丙烯酯)体系、聚(碳酸乙烯酯)体系和聚(碳酸亚乙烯酯)体系等,并详细阐述了上述每种聚碳酸酯基固态聚合物电解质的制备、电化学性能、优缺点及改性手段,归纳出其离子配位-解配位过程和离子扩散机制,还对聚碳酸酯基固态聚合物电解质的未来发展方向和研究趋势望进行了预测和展望.     

Conductivity enhancement mechanism of the poly(ethylene oxide)/modified‐clay/LiClO4 systems

This study demonstrates that adding clay that was organically modified by dimethyldioctadecylammonium chloride (DDAC) and d2000 surfactants increases the ionic conductivity of polymeric electrolyte. A.C. impedance, differential scanning calorimetric (DSC), and Fourier transform infrared (FTIR) studies revealed that the silicate layers strongly interact with the dopant salt lithium perchlorate (LiClO₄) within a poly(ethylene oxide) (PEO)/clay/LiClO₄ system. DSC characterization verified that the addition of a small amount of the organic clay reduces the glass‐transition temperature of PEO as a result of the interaction between the negative charge in the clay and the lithium cation. Additionally, the strength of such a specific interaction depends on the extent of PEO intercalation. With respect to the interaction between the silicate layer and the lithium cation, three types of complexes are assumed. In complex I, lithium cation is distributed within the PEO phase. In complex II, lithium cation resides in an PEO/exfoliated‐clay environment. In complex III, the lithium cation is located in PEO/agglomerated‐clay domains. More clay favors complex III over complexes II and I, reducing the interaction between the silicate layers and the lithium cations because of strong self‐aggregation among the silicate layers. Notably, the (PEO)₈LiClO₄/DDAC‐modified clay (DDAC‐mClay) composition can form a nanocomposite electrolyte with high ionic conductivity (8 × 10^?5 S/cm) at room temperature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1342–1353, 2002     

含硅氢键聚二硅氧烷/聚醚共混聚合物电解质 II. PSEMH对PEO结晶性能及离子电导率的影响

通过Raman,DSC和XRD等方法对PEO-PSEMH-LiClO4全固态共混聚合物电解质进行了研究,结果表明PSEMH能够显著地降低PEO-LiClO4电解质体系的PEO的结晶性和玻璃化转变温度,同时PSEMH分子的二硅醚链节中氧原子与Li+间具有配位作用,从而大幅提高x%PEO-y%PSEMH-LiClO4电解质在低温区的离子电导率。而当PSEMH交联硫化之后,虽然降低了PEO的结晶度和Tg,但是由于PSEMH的交联网络限制了聚合物链段的运动性,使得电解质的离子电导率在低温区高于100%PEO-LiClO4(约为12倍),而在高温区则低于100%PEO-LiClO4,充分证明了PSEMH对电解质的离子电导率的具有显著的贡献作用。     

Architecture and solution properties of amphiphilic polymer brushes with peripheral charged ions

Functionalized poly(ethylene oxide) (PEO) macromonomers (alpha -tertiary amino and omega -methacryloyl groups) were prepared by ring-opening polymerization of live PEO anions end-capped with styrene oxide using 2-[2-(N ,N -dimethylamino)-ethoxy]ethanol potassium alkoxides as an initiator with methacryloyl chloride. PEO brushes were synthesized by free-radical homopolymerization of such PEO macromonomers. These brushes were converted into peripherally charged brushes by quaternization. We studied the solution properties of both types of brushes from the viewpoint of charge effect. It was found from dynamic light scattering (DLS) that the polymer brushes formed a single macromolecule in solution due to crowding of side chains. It was speculated from angular dependence measurements that the polymer brushes with large aspect ratios took a geometrical anisotropic conformation such as a cylinder. In methanol with a low dielectric constant, radius of gyration (R(G)), and cross-sectional radius of gyration (R(G,C)) of the polymer brushes with charged side chains were smaller than those of the polymer brushes without charges. In a solvent with a low dielectric constant such as methanol, ionic groups do not dissociate and condense. On the other hand, these physical values in an aqueous solution were somewhat larger than those of the polymer brushes without charges. In water with a high dielectric constant, peripherally charged brushes were strongly stabilized by electric double layers.