Effects of lithium salt and poly(4‐vinyl phenol) on crystalline and amorphous phases in poly(ethylene oxide)

Effects of a strong‐interacting amorphous polymer, poly(4‐vinyl phenol) (PVPh), and an alkali metal salt, lithium perchlorate (LiClO₄), on the amorphous and crystalline domains in poly(ethylene oxide) (PEO) were probed by differential scanning calorimetry (DSC), optical microscopy (OM), and Fourier transform infrared spectroscopy (FTIR). Addition of lithium perchlorate (LiClO₄, up to 10% of the total mass) led to enhanced T_g's, but did not disturb the miscibility state in the amorphous phase of PEO/PVPh blends, where the salt in the form of lithium cation and ClO anion was well dispersed in the matrix. Competitive interactions between PEO, PVPh, and Li⁺ and ClO ions were evidenced by the elevation of glass transition temperatures and shifting of IR peaks observed for LiClO₄‐doped PEO/PVPh blend system. However, the doping distinctly influenced the crystalline domains of LiClO₄‐doped PEO or LiClO₄‐doped PEO/PVPh blend system. LiClO₄ doping in PEO exerted significant retardation on PEO crystal growth. The growth rates for LiClO₄‐doped PEO were order‐of‐magnitude slower than those for the salt‐free neat PEO. Dramatic changes in spherulitic patterns were also seen, in that feather‐like dendritic spherulites are resulted, indicating strong interactions. Introduction of both miscible amorphous PVPh polymer and LiClO₄ salt in PEO can potentially be a new approach of designing PEO as matrix materials for electrolytes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3357–3368, 2006     

Conductivities and spectroscopic studies on hyperbranched polyurethane electrolytes

Polymer electrolytes were prepared with hyperbranched polyurethane, linear polyurethane as the host polymer, and lithium perchlorate (LiClO₄) as the ion source. Fourier transform infrared spectra were used to analyze the bonding degree of Li⁺ with carbonyl and ether groups. Raman spectra were applied to analyze the aggregate degree of anion perchlorate ion (ClO). The spectra analysis indicated that the hyperbranched polyurethane could function as a “solvent” for the lithium salt. Also, the conductivity increased with increasing concentration of hyperbranched polymers in the host polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 120–126, 2003     

A Study of the dielectric properties of the polymer electrolyte PEO-LiClO4 over a composition range using time domain spectroscopy

High frequency dielectric measurements in the range 10 MHz to 10 GHz have been performed on poly(ethylene oxide) (PEO) and its complexes with lithium perchlorate using time domain spectroscopy. Measurements were made over a wide polymer-to-salt composition range and in the temperature range 50–75°C. All samples were amorphous. A relaxation was observed for PEO and its complexes with LiClO₄ in the GHz region and is attributed to the β (α_a) relaxation arising from long-range segmental motion of the polymer or the ion-polymer complex. Good agreement was found between conductivity values determined by TDS and those quoted in the literature An increase in salt concentration in the polymer increases the distribution of relaxation times which may be explained in terms of increased intermolecular and intramolecular transient crosslinks. The dispersion amplitude (ε?ε) has a maximum value between an O/Li ratio of 20:1 and 12:1 and shows a similar dependence on salt concentration as the conductivity.     

Solid polymer electrolytes X: Preparation and characterizations of polyether–siloxane,organic–inorganic,hybrid nanocomposites complexed with lithium perchlorate

Organic–inorganic hybrid nanocomposites of poly(ethylene glycol)/siloxane were obtained via the sol–gel approach. In these composites, nanometric siloxane heterogeneity was embedded into a polymer matrix with a covalent bond at the interfaces. The ²⁹Si magic-angle spinning (MAS) spectrum exhibited a high degree of condensation through the relative abundance of T⁰ [RSi(OR)₃], T¹ [RSi(OR)₂(OSi)], T² [RSi(OR)(OSi)₂], and T³ [RSi(OSi)₃] silicone nuclei. The effect of lithium salt concentration on ionic interaction, conductivity, and thermal properties of these composite electrolytes were investigated by Fourier transform infrared spectroscopy, DSC, thermogravimetric analysis, alternating current impedance, and solid-state ⁷Li MAS NMR measurements. These observations indicated that the different types of complexes by the interactions of Li⁺ and ClO ions are formed within a hybrid host, and the formation of transient crosslinks between Li⁺ ions and the ether oxygens results in an increased glass-transition temperature of the polyether segment and decomposed rate of composite electrolyte. ⁷Li MAS NMR measurements revealed the changes in line shape of lithium resonances with different LiClO₄ contents, suggesting that a significant degree of ionic association is present in the polymer-salt complexes. The behavior of ion transport in these composite electrolytes was correlated with the interactions between ions and polymer host. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1928–1937, 2004     

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     

Counterion binding to poly(allylammonium) cation

Chloride ion activity coefficients in aqueous solutions of poly(allylamine) hydrochloride (PAA · HCl) have been determined both in the absence and the presence of simple salts. Without added salt, the activity coefficient depends on the polymer concentration. With added salt, the binding of added counterions by PAAH⁺ is evaluated from the release of chloride ion. The extent of interaction between counterions and PAAH⁺ at a given polymer concentration decreases in the order SO ? ClO > NO > Cl^? > Br^? > I^?. This order of counterion selectivity agrees with the previous estimation of potentiometric titrations. The result shows that the hydration of the counterion, as well as its charge, plays an important part in counterion binding to the polyion.     

Polyelectrolyte-like behavior of polyethylene oxide/LiClO4 mixture in chloroform or chloroform/dimethylformamide mixed solvent

Lithium perchlorate (LiClO₄) was dissolved in dehydrated chloroform with polyethylene oxides (PEO) having different molecular weights. The mixing ratio of ether oxygen unit (? O? ) of PEO to cation (Li⁺) was set to 20:1. The solution viscosity of the PEO/LiClO₄ mixtures was measured using an Ubbelohde viscometer at 30.0°C. The concentration dependence of the reduced viscosity was analyzed by diluting the initial PEO/LiClO₄ mixed solution with pure chloroform to keep the ratio of ? O? to Li⁺ constant. The increase in the reduced viscosity for a dilute solution was found in every mixture system, but not in the PEO solution without salt. Similar experiments were also carried out in chloroform/dimethylformamide (DMF) mixed solvent (4:1 by volume). These results were analyzed using the Fuoss equation, which was applied for the analysis of a polyelectrolyte aqueous solution. Linear relations are depicted in the Fuoss plots, suggesting that the PEO/LiClO₄ mixture shows polyelectrolyte-like behavior in chloroform or in chloroform/DMF mixed solvent. This is attributed to the intramolecular electrostatic repulsion of lithium cations which are trapped by the PEO chains through ion–dipole interaction.     

Ionic conductivities of the complexes of LiClO4 and alternating copolymers of oligomeric poly(ethylene oxide) having biphenyl units in the backbone

A series of copolymers of predominantly poly(ethylene oxide) (PEO) with biphenyl (BP) units in the backbone were synthesized. The solid polymer electrolytes (SPEs) were prepared from these copolymers (BP-PEG) employing lithium perchlolate (LiClO₄) as a lithium salt and their ionic conductivities were investigated to exploit the structure–ionic conductivity relationships as a function of chain length ratio between the flexible PEO chains and rigid BP units. The ionic conductivity increases with increasing PEO length in BP-PEG. The salt concentrations in BP-PEG/LiClO₄ complexes were also changed and the results show that maximum conductivity is obtained at [EO]/[Li⁺]≈8. The reasons for these findings are discussed in terms of the number of charge carriers and the mobility of the polymer chain.     

Influence of Humidity on the Complex Structure of PEO-Lithium Salt Polymer Electrolyte

Solid polymer electrolytes of PEO/LiClO₄ and PEO/LiTFSI solution casting films were prepared with the EO/Li molar ratio of 3: 1, and the effect of relative humidity (RH) on their complex structures were characterized. It is shown that the complex structures were barely changed at RH ≤ 10% while severe differences were shown at RH ≥ 20%. The reason was attributed to the interactions of water with lithium salt, and the formation of PEO–Li⁺–H₂O decreased the interactions between PEO and lithium ions. Furthermore, it was shown that the hydrated samples after heat treatment were still strikingly different in characters from their anhydrous precursors, and the type of lithium salt affected the final structures. It was found that the structure of (PEO)₃LiClO₄ (30% RH) was hardly changed after heating; however, an irreversible compositional transition was discovered in (PEO)₃LiTFSI (30% RH) in which case (PEO)₂LiTFSI was formed.     

Vibrational Spectroscopic Study on Ion Solvation and Association of Lithium Perchlorate in 4-Methoxymethyl-ethylene Carbonate

Solvation interaction and ion association in solutions of lithium perchlorate/4-methoxymethyl-ethylene carbonate （MEC） have been studied by using Infrared and Raman spectra as a function of concentration of lithium perchlorate. The splitting of ring deformation band and ring ether asymmetric stretching band, and the change of carbonyl stretching band suggest that there should be a strong interaction between Li^＋ and the solvent molecules, and the site of solvation should be the oxygen atom of carbonyl group. The apparent solvation number of Li^＋ was calculated by using band fitting technique. The solvation number was decreased from 3.3 to 1.1 with increasing the concentration of LiClO4/MEC solutions. On the other hand, the band fitting for the ClO4^- band revealed the presence of contact ion pair, and free ClO4^- anion in the concentrated solutions.     

Factors affecting the complexation of polyacrylic acid with uranyl ions in aqueous solutions: A luminescence study

A study was carried out in aqueous solutions using luminescence technique to investigate the effects of pH, salt concentration, and temperature on the polyacrylic acid/uranyl ion (PAA/UO) complex formation as well as competitive phenomena of enhancement and quenching effects on photoexcited state of uranyl ions. It was found that excess of H⁺ and OH^? is not favorable for complexation between uranyl ions and polymer. Added nitrate salts of Na⁺ and K⁺ had significant enhancement effect on emission spectra of PAA/UO complex. These results indicated that the metal ion/polymer chain complex collapsed by addition of salts and then complex became more compact with consequent phase separation. No significant effect of temperature on the PAA/UO complex stability has been observed between 25–50 °C. The quenching rate constants obtained from Stern–Volmer plots were found to be in the order of k_q(H⁺) >> k_q(K⁺) > k_q(Na⁺). © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2737–2744, 2005     

Single Lithium‐Ion Conducting Polymer Electrolytes Based on a Super‐Delocalized Polyanion

A novel single lithium‐ion (Li‐ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4‐styrenesulfonyl)(trifluoromethyl(S‐trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI^?), and high‐molecular‐weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass‐transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li‐ion transference number (t_Li⁺=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li‐ion conductivity as high as 1.35×10^?4 S cm^?1 at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.     

Vibrational spectroscopy analysis of ion conduction mechanism in dispersed phase polymer nanocomposites

A novel combination of dispersed phase polymer nanocomposite electrolyte based on PEO₈‐LiClO₄+ x wt % nano‐CeO₂ has been investigated. A model for ion transport mechanism has been proposed to account for substantial enhancement of its electrical conductivity by ～ 2 orders of magnitude at low volume fraction of the filler reinforcement in the polymer nanocomposite films. The strength of the proposed model is based on unambiguous evidences from FTIR, TEM, and conductivity analysis. The FTIR results provide clear role of nanofiller concentration on ion–ion interaction quantified in terms of the fraction of free anion and ion‐pairs present in the nanocomposite films and its excellent correlation with conductivity versus filler concentration. The presence of asymmetry in the ν₄(ClO₄^?) band observed at 625 cm^?1 is attributed to its resolved degeneracy suggesting the presence of both uncoordinated and cation‐coordinated ClO₄^? anion in the matrix due to ion–ion and ion–filler interactions assisted by Lewis acid–base interaction. The enhancement in conductivity at low concentration is possibly due to direct interaction of nano‐CeO₂ with both polymer host and anions resulting in the release of ionic charges. Drastic conductivity reduction at higher concentration is related to charge immobilization because of ion/ion‐pair entrapment by local clusters of filler as evidenced in TEM. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 60–71, 2009     

Anionic polymerization of N-substituted maleimide. V. A study on the kinetic features of anionic polymerization of N-phenylmaleimide

The kinetic feature of the anionic polymerization of N-PMI was investigated in THF. The polymerization system initiated with lithium tert-butoxide was revealed to be so-called “slow-initiation” system. The rate constant of the initiation reaction, k_i, was obtained to be 4.2 × 10^?3 (L mol^?1 s^?1) at ?72°C. The apparent rate constants of the propagation reaction, k, at ?72°C were individually obtained from each slope of the first-order plots in the later stages of the polymerizations for four different initiator concentrations. Each k is fairly close to that of initiation rate around 10^?3. The propagation reaction was concluded to be dominated by ion-pair mechanism from the analysis of the kinetic data and the results of the addition effects of crown ether and common salt.     

Thermoresponsive PPEGMEA‐g‐PPEGEEMA well‐defined double hydrophilic graft copolymer synthesized by successive SET‐LRP and ATRP

A series of well‐defined double hydrophilic graft copolymers containing poly[poly(ethylene glycol) methyl ether acrylate] (PPEGMEA) backbone and poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) side chains were synthesized by the combination of single electron transfer‐living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained comb copolymer was treated with lithium diisopropylamide and 2‐bromoisobutyryl bromide to give PPEGMEA‐Br macroinitiator. Finally, PPEGMEA‐g‐PPEGEEMA graft copolymers were synthesized by ATRP of poly(ethylene glycol) ethyl ether methacrylate macromonomer using PPEGMEA‐Br macroinitiator via the grafting‐from route. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept narrow (M_w/M_n ≤ 1.20). This kind of double hydrophilic copolymer was found to be stimuli‐responsive to both temperature and ion (0.3 M Cl^? and SO). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 647–655, 2010     

Beiträge zur Chemie des Hydrazins und seiner Derivate. XVIII. Darstellung und Eigenschaften von Salzen des Triazans

The reaction of N₃H₇SO₄ with barium compounds BaX₂ in aqueous solutions yields under precipitation of BaSO₄ solutions which contain the corresponding salts of triazane N₃H₆X (X = NO, ClO, Cl^?, CH₃COO^?, N₃, CN^?, Br^?, OH^?). Due to the instability of the triazanium ion, NH₂? NH₂? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document}H₂, the solid triazanium salts could only be isolated in mixture with the also formed BaSO₄. The properties of these compounds are described.     

Effects of PEO length and phenyl unit structure on ionic conductivities of the complexes of LiClO4 and alternating copolymers of PEO having various phenyl units in the backbone

A series of copolymers of predominantly poly(ethylene oxide) (PEO) with mono-phenyl (HQ), biphenyl (BP) units, or both of them (HQ/BP) in the backbone were synthesized. The solid polymer electrolytes (SPEs) were prepared from three different types of copolymers (HQ-PEG, BP-PEG, and HQ/BP-PEG) employing lithium perchlorate (LiClO₄) as a lithium salt at a fixed salt concentration of [EO]/[Li⁺]=8. Their ionic conductivities were investigated to exploit the structure–ionic conductivity relationships as a function of structural change in rigid phenyl units and chain length ratio between flexible PEO chain and rigid phenyl units. As more rigid phenyl units were incorporated in the backbone chain, the formation inter- and intra-molecular complex with LiClO₄ became weaker and lower ionic conductivities were observed. And it was also found that higher ionic conductivity is obtained with increasing PEO chain length because inter- and intra-molecular dissociation power of PEO increases.     

A Unified Interpretation of Kinetic Data on the Acid-Induced Cleavage and of Product-Analysis Data on Spontaneous Cleavage of the Mono-ol Cation μ-Hydroxo-bis[pentaamminecobalt(III)] ([(NH3)5CoOHCo(NH3)5]5+)

Recent work on the spontaneous (= acid-independent) cleavage of the mono-ol cation, i.e. in Cl^?/ClO and NO/ClO mixed-electrolyte media has established (by analysis of anion-competition experiments) the existence of reactive ion pairs of the mono-ol cation with Cl^? and NO. Their existence must be allowed for in the analysis of the rate data for the acid-induced cleavage (pH 0–1) of the mono-ol cation in these mixed-electrolyte media. Thus, previous data for acidic Cl^?/ClO media have been re-interpreted in this work, and new data for NO/ClO media have been analyzed in the same sense. This analysis removes an apparent discrepancy in the orders of magnitude of ion aggregate stability constants between the mono-ol and similar binuclear cations.     

Structural analysis of aggregates formed by a thermoresponsive homopolymer in dilute aqueous solutions

The aqueous solution of a thermoresponsive polymer, poly[2‐(2‐ethoxy) ethoxyethyl vinyl ether] poly(EOEOVE), contains a tiny amount of large polymer aggregates at low polymer concentrations far below the lower critical solution temperature (～40 °C). The molar mass M_w,slow, radius of gyration 〈S²〉, and hydrodynamic radius R_H,slow of the aggregating component of poly(EOEOVE) were obtained by simultaneous static and dynamic light scattering as functions of the polymer concentration and temperature, while the weight fraction w_slow of the component was estimated by size‐exclusion chromatography. The M_w,slow dependencies of 〈S²〉 and R_H,slow, as well as the ratio 〈S²〉/R_H,slow, indicated that the poly(EOEOVE) aggregate takes a sparsely branched polymer‐like conformation. We have analyzed the structure of the aggregate, using the branched polymer model of random type. The M_w,slow dependence of 〈S²〉 obtained was favorably compared with this model with reasonable structural parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1179–1187, 2006     

Synthesis of a novel one‐pot approach of hyperbranched polyurethanes and their properties

A new method for the synthesis of hyperbranched polymers involving the use of AB_x macromonomers containing linear units have been investigated. Two types of novel hyperbranched polyurethanes have been synthesized by a one‐pot approach. The structures of monomers and polymers were characterized by elemental analysis, ¹H NMR, ¹³C NMR, Fourier transform infrared spectroscopy, gel permeation chromatography, and thermogravimetric analysis. The hyperbranched polymers have been proven to be extremely soluble in a wide range of solvents. Polymer electrolytes were prepared with hyperbranched polymer, linear polymer as the host, and lithium perchlorate (LiClO₄) as the ion source. Analysis of the isotherm conductivity dependence of the ion concentration indicated that these hyperbranched polymers could function as a “solvent” for the lithium salt. The conductivity increased with the increasing concentration of hyperbranched polymers in the host polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 344–350, 2002