Study on a comb-like polymer electrolyte based on the backbone of ethylene-maleic anhydride copolymer

A comb-like polymer host(CBPE) as polymer electrolyte was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with ethylene-maleic anhydride copolymer(EMAC) and endcapping the residual carboxylic acid with methanol. The synthetic process was followed by IR and the amorphous product characterized by IR and elemental analysis. There were two peaks in the plot of the ionic conductivity against Li salt concentration. The plot of log sigma vs. 1/(T - T-0) may exhibit dual VTF behavior when using the glass transition temperature of PEO of side chain as T-0. The comb-like polymer is a white rubbery solid which dissolves in acetone. (C) 1998 Elsevier Science B.V. All rights reserved.

A study on the diffusion of quinhydrone in polymer electrolyte

The diffusion coefficients (D) of quinhydrone were estimated in polymer electrolytes by using non-steady-state chronoamperometry and steady-state current voltammetry. The D values have been estimated in polyethylene glycol (PEG) containing different concentrations, and cations of supporting electrolytes, and in different solvents over a range of temperatures. The dependencies of electroactive probe diffusion coefficients on temperature, supporting electrolyte concentration and polymer chain length are discussed. The results show that D increases with increasing temperature and decreasing concentration of supporting electrolyte. The diffusion coefficient depends strongly on the length of polymer chain and decreases sharply with increasing polymer chain length. The contribution of electron self-exchange has been explored and it seems to be negligible here. (C) 1998 Elsevier Science S.A.

Polymerization of ethylene by zirconocene-B(C6F5)(3) catalysts with aluminum compounds

Ethylene polymerization by zirconocene-B(C6F5)(3) catalysts with various aluminum compounds has been investigated. It is found that the catalytic activity depended on zirconocenes used, and especially on the type of aluminum compounds. For Et(H(4)Ind)(2)ZrCl2 (H(4)Ind : tetrahydroindenyl), the activity decreases in the following order: Me3Al > i-Bu3Al > Et3Al much greater than Et2AlCl. While for Cp2ZrCl2(Cp : cyclopentadienyl), it varies as follows: i-Bu3Al > Me3Al much greater than Et3Al. Furthermore, the activity is significantly affected by the addition mode of the catalytic components, which may imply that the formation of active centers is associated with an existing concentration of catalytic components. Results of thermal behavior of polyethylene (PE) studied by differential scanning calorimetry(DSC) show that crystallinity of the polymer prepared with Et3Al is higher than that with Me3Al or i-Bu3Al. It is also found that the number-average molecular weight ((M) over bar) of the polymers prepared with Me3Al or i-Bu3Al is much higher than that with Et3Al. H-1-NMR studies substantiate that i-Bu3Al is a more efficient alkylation agent of Cp2ZrCl2 in comparison with Me3Al. (C) 1997 John Wiley & Sons, Inc.

Dynamic mechanical properties of interpenetrating polymer networks based on polyacrylates and epoxy

Interpenetrating polymer networks (IPNs) based on polyacrylate (poly(polyethylene glycol diacrylate), PEGDA) and epoxy(diglycidyl ether of bisphenol A, DGEBA) were prepared simultaneously Dynamic mechanical properties of the SINs (simultaneous interpenetrating networks) with various compositions were studied. Enhanced mechanical properties were found in this case. From the point of view of pre-swollen networks, all of the PEGDA/DGEBA IPNs were composed of the individual pre-swollen networks. A micro-phase segregation system was produced in the SIN. Glass transition temperatures shifted inward, which was attributed to molecular packing effects or mutual-entanglements of molecular segments among the individual pre-swollen networks. In accordance with the additivity of properties, namely the parallel model, the entanglement density between the two polymer networks reached its maximum at 50/50 PEGDA/DGEBA IPN.

Studies on the two class glass transition and the typical VTF behaviour of an amorphous comb polymer electrolyte

A comb polymer (CP350) with oligo-oxyethylene side chains of the type -(CH2CH2O)(7)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly(ethylene glycol) methyl ether. The polymer can dissolve LiNO3 salt to form homogeneous amorphous polymer electrolyte. This electrolyte system was first found to have two class glass transitions, and the two T(g)s were observed to increase with increasing salt content. The ionic conduction was measured by using the complex impedance method, and conductivities were investigated as functions of temperature and salt concentration. At 25 degrees C, the ionic conductivity maximum of this system can get to 3.72 X 10(-5) S/cm at the [Li]/ [EO] ratio of 0.057. The appearance of the conductivity maximum has been interpreted as being due to the effect of T-g and the so called physical crosslinks. The temperature dependence of the ionic conductivity displaying non-Arrhenius behaviour can be analyzed using the Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model.

A study of cokes used as anodic materials in lithium ion rechargeable batteries

A variety of cokes pretreated at different temperatures are used as anodic materials and their electrochemical characteristics are examined by cyclic voltammetry. It is found that for some cokes such as petroleum coke (preheated at 1300 degrees C), pitch coke (1300 degrees C), needle coke (1900 degrees C), metallurgical coke (1900 degrees C), high capacity and cyclic efficiency are achieved. Needle coke (1900 degrees C) and metallurgical coke (1900 degrees C) in particular give a capacity of over 200 mAh/g and a cyclic efficiency of nearly 100%, whereas poor performance is exhibited by those pretreated at higher or lower temperatures, e.g., petroleum cokes (500 degrees C, 2800 degrees C), pitch coke (500 degrees C) and needle coke (2800 degrees C). The cyclic voltammograms show two electrochemical processes, one at about 0.1 V vs. Li+/Li which is electrochemically reversible, and may be attributed to the intercalation/deintercalation of lithium ions while the other, at about 0.6 V vs. Li+/Li, is electrochemically irreversible and may be assigned to the decomposition of the electrolyte solvent, which leads to formation of the passive film on the anode surface. The experimental results strongly suggest that the pretreatment temperature of cokes and of the solvent are determining factors for the growth, structure and properties of the passive film.

Lithium ion conducting polymer electrolytes based on alternating maleic anhydride copolymer with oligo-oxyethylene side chains

A comb polymer with oligo-oxyethylene side chains of the type -(CH2CB2O)(12)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly (ethylene glycol) methyl ether. The polymer can dissolve LiClO4 salt to form homogeneous amorphous polymer electrolyte. The ac ion conduction was measured using the complex impedance method, and conductivities were investigated as functions of temperatures and salt concentration. The complexes were first found to have two classes of glass transition which increase with increasing salt content, The optimum conductivity attained at 25 degrees C is in the order of 5.50 x 10(-6)Scm(-1). IR spectroscopy was used to study the cation-polymer interaction.

A study of the dependence of ferrocene diffusion on chain length in polymer electrolytes

The diffusion rates of ferrocene have been estimated in five kinds of poly(ethylene glycol) solution, containing the electrolyte LiClO4, by using non-steady-state chronoamperometry. The D-app of ferrocene increases with increasing temperature, and the dependency of D-app on temperature obeys the Williams-Landel-Ferry equation. The D-app of ferrocene decreases with increasing polymer chain length. Both the chain length and temperature dependence conform to a simple free volume model. A relation between current and polymer chain length is suggested at room and high temperatures.

Rheological properties and crystallization behavior of yttrium oxide filled low ethylene content polypropylene copolymer

The rheological properties and crystallization characteristics of low ethylene content poly propylene (EPM) with and without Yittrium oxide (Y2O3) as a filler was investigated by cone-plate viscometer and differential scanning calorimetry. Yittrium oxide had a profound effect on the viscosities of the systems. To determine the nonisothermal crystallization rate of the materials, a new estimation method was used. From the results, we can conclude that Y2O3 acts as a nucleating agent, which increased the crystallization rate of the EPM. (C) 1996 John Wiley & Sons, Inc.

Studies on water-swellable elastomer .1. Synthesis and characterization of amphiphilic polymer

A new amphiphilic polymer i.e., polyethylene glycol (PEG) grafted crystalline neoprene, which was used as compatibilizer to improve the compatibility of elastomer and water-absorbent resin, has been investigated. The synthesis was based on the reaction between chlorine in neoprene and sodium salts of PEG. PEGs with molecular weights of 600 and 2000 were used. The grafting percent and the PEG content were calculated through elemental analysis of chlorine in the resulted copolymers. The maximum grafting percent of copolymers was ca. 24.80%. The molecular parameters such as number-average molecular weight and the average number of grafting chains on one CR backbone were also calculated and discussed. (C) 1996 John Wiley & Sons, Inc.

Synthesis and characterization of interpenetrating polymer networks based on polyacrylate and epoxy

The synthesis and properties of simultaneously interpenetrating networks (SINs) based on poly(polyethylene glycol diacrylate) (PEGDA) and epoxy (diglycidyl ether of bisphenol A, DGEBA) were studied. The effect of compositional variation on the morphology and properties of products was investigated. The swelling coefficient, densities, glass transition behavior, and thermal stability of these interpenetrating networks (IPNs) are discussed. Microphase separation morphological structures were found in all PEGDA/DGEBA IPNs. Decreased swelling ratios compared to the calculated swelling coefficients based on the weight additivity of the components were obtained after the formation of IPNs. Increased density and thermal stability were also obtained in these IPNs, implying the existence of interpenetration (topological entanglements) among the component networks.

A study of the dependence of ferrocene diffusion on electrolyte concentration and size in a polymer medium using non-steady-state chronoamperometry

This article describes a quantitative study of the diffusion rate of ferrocene(Fc) dissolved in ploy(ethylene glycol)(PEG) medium containing MClO(4)(M = Li+, Na+, Bu(4)N(+), Hx(4)N(+)). The apparent diffusion coefficient D-app and the active concentration c(a) of Fc were simultaneously measured by using non-steady-state chronoamperometry. The D-app and c(a) of Fc have been estimated in PEG containing different concentrations and sizes of supporting electrolyte, and the dependence of D-app on ferrocene concentrations has been observed. The values of D-app decrease with increasing concentrations of Fc, increasing concentrations of LiClO4 or the ratio (O:Li) and also with 4 decreasing cation radius of the electrolyte. The temperature dependencies conform to a simple free volume model. The concentration and size of the counterion dependencies of the diffusion rate are similar to the behavior of their dependencies of ionic conductivity in polyelectrolyte.

An investigation on ion solvation and ion association in a gel-type solid state polymer electrolyte

Ion salvation and ion association in polytriethylene glycol dimethacrylate (PTREGD)-LiClO4 gel-type polymer electrolytes were investigated. It was found that the fraction of solute existing as single ions (alpha(i)) decreases and that of triple ions (alpha(i)) increases linearly with increasing LiClO4 concentration, while for ion pairs, as the salt concentration increases, its fraction (alpha(p)) increases first and then falls down. The findings can be rationalized by the fact that the ionic conductance of the polymer electrolyte may be mainly contributed by triple ions and higher ionic aggregates with unequal numbers of positive and negative charges in the salt concentration range of practical significance, i.e. in the range of 0.5-1.5 mol/l. The temperature dependence of these fractions was also examined. In the case of tetraethylene glycol as the solvent, alpha(i) and alpha(p) increase as the temperature is raised, but alpha(t) decreases as the temperature increases from 25 degrees C to 85 degrees C. It seems that the increase of alpha(i) and alpha(p) results from the redissociation of triple ions at higher temperature, The same changing trend of those fractions is also observed when PEG(400) is used as the solvent.

Preparation and crystal structures of LaCl3(15-crown-5) and [LaCl2(phen)(H2O)(2)(mu-Cl)](2)center dot(15-crown-5)center dot MeCN

LaCl3(15-crown-5), I was prepared by the reaction of LaCl(3)nH(2)O with 15-crown-5 and bipy (2,2'-bipyridyl). [LaCl2(phen)(H2O)(2)(mu-Cl)](2) .(15-crown-5). MeCN, II, was crystallized from a mixture of LaC1(3) . nH(2)O, phen (1,10-phenanthroline) and 15-crown-5 in MeOH/MeCN, Crystal structures of these two complexes have been determined by X-ray methods. The La(III) ion in I is coordinated by three Cl anions and five oxygen atoms of a crown ether. The two metal ions in II are bridged by two Cl anions and the crown ligand is hydrogen-bonded to the coordinated water molecules to form polymeric... crown/cation/cation/crown... chains.

SYNTHESIS AND CHARACTERIZATION OF A NEW COMB-LIKE POLYMER-BASED ON POLY(VINYL METHYL ETHER-ALT-MALEIC ANHYDRIDE) BACKBONE

A new comblike polymer host for polymer electrolyte was synthesized by reacting monomethyl ether of poly(ethylene glycol) with poly(vinyl methyl ether-alt-maleic anhydride) and endcapping the residual carboxylic acid with methanol. Butanone was selected as a solvent for the esterification in order to obtain a completely soluble product. The synthesis process was traced through by LR. Compared with the model compounds, the presumed structure of this comblike polymer has been proved to be valid by C-13 NMR The comb polymer is a white rubbery solid. It can be dissolved in butanone and THF, and manifests good film forming ability.