Positron annihilation in ionic conductivity polymers

Wang, S. J.; Wang, B.; Li, S. Q.; Zhang, Peng

doi:10.1007/bf02036264

Cited by 4 publications

(2 citation statements)

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“…First studies of the free volume in relationship to the ionic conductivity indicate that the temperature dependence of the ionic conductivity can be explained by free volume changes. Wang et al , found a correlation of the fractional free volume and the conductivity of polyether urethane−LiClO 4 complexes for temperatures above the glass transition of the polymer. However, the mobility of cations and anions in polymer electrolytes depends also on the interaction of the polymer and the charge carriers.…”

Section: Introductionmentioning

confidence: 99%

“…Besides changes in the charge carrier mobility, the ionic conductivity is furthermore influenced by the number of charge carriers with dependence on the ionic association. Therefore, changes of the ionic conductivity with dependence on the salt content and the role of the plasticizer could not fully be understood by PAL spectroscopic measurements only. − For example, Forsyth et al , found that the addition of propylene carbonate or olig(ethylene glycol) 4 dimethyl ether ((EG) 4 DME) to polyether urethane networks results in a similar increase in the free volume; however, the ionic conductivity was effected in a different manner.…”

Section: Introductionmentioning

confidence: 99%

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Local Free Volume and Structure of Polymer Gel Electrolytes on the Basis of Alternating Copolymers

et al. 2000

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The relationship between the structure of the polymer and the charge carrier mobility and the ionic conductivity has been studied for a new class of gel electrolytes on the basis of alternating copolymers. These gel electrolytes were prepared by photopolymerization of maleic anhydride and oligo(ethylene glycol) 4 divinyl ether in the presence of various oligo(ethylene glycol) n dimethyl ethers with molar masses between 134 and 2000 g/mol, and LiCF 3 SO 3 . Thermal properties of the materials were studied by differential scanning calorimetry and dynamic mechanical analysis, which additionally gives structural information. Changes in the free volume as a function of the content of the plasticizer and the salt were studied by positron annihilation lifetime (PAL) spectroscopy. The self-diffusivity of charge carriers and plasticizer in the gel electrolytes was investigated by pulsed field gradient NMR. The ionic conductivity and its pressure dependence were determined by the impedance technique. The gel electrolytes studied are heterogeneous materials composed of a highly crosslinked polymer network (M c ≈ 600 g/mol) with a T g ≈ 100 °C and of a plasticizer-salt solution with a T g ≈ -70 °C. Hence, two hole size distributions were measured by PAL spectroscopy around 0.26 and 0.34 nm related to the network and the liquid phase, respectively. The activation volume V* calculated from the pressure dependence of the ionic conductivity was V* ) 22.7 cm 3 /mol. It is concluded that the charge carrier transport occurs in the liquid phase of the gel electrolytes. However, the network is too dense to provide sufficient distribution and mobility of the plasticizer-salt solution. Self-diffusivity and conductivity of the gel electrolytes studied are not related according to the Nernst-Einstein equation. The ortho-positronium (o-Ps) lifetime τ 3 and its intensity I 3 in the gel were found to be changed if salts were added to the gel. The o-Ps lifetime is discussed in terms of o-Ps bubbles in the plasticizer-salt solution. The o-Ps intensity I 3 , which decreases with the salt concentration, mirrors inhibition reactions of the o-Ps formation attributed to the anions of the salt.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Local Free Volume and Structure of Polymer Gel Electrolytes on the Basis of Alternating Copolymers

et al. 2000

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Anion exchanged polymerized ionic liquids: High free volume single ion conductors

Elabd

2011

Polymer

174

204

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The local free volume, glass transition, and ionic conductivity in a polymer electrolyte: A positron lifetime study

Bamford

Dlubek

Reiche

et al. 2001

The Journal of Chemical Physics

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The size of free-volume holes in neat poly[(ethylene glycol)23dimethacrylate] [poly((EG)23DMA)] and in the same polymer doped with 0.6 mol/kg LiCF3SO3 have been studied as a function of temperature in the range between 100 and 370 K using positron annihilation lifetime spectroscopy. The results are compared with differential scanning calorimetry and ionic conductivity measurements. In both systems, the hole volume νh shows a typical glass-transition behavior, i.e., a small linear increase with temperature below the glass transition temperature Tg and a steeper increase above Tg. From these measurements Tg was estimated to be 233 K (neat polymer) and 240 K (polymer with salt) and the coefficients of the thermal expansion of the hole volume were determined. The fractional free volume (f=0.080) and the number density of holes (Nh=0.6 nm−3) were also estimated. Below Tg the average hole volume of the polymer electrolyte is larger than in the neat polymer. This is consistent with the bulky character of the CF3SO3− anion. Above Tg the salt-doped system shows the lower hole volume of the two systems, probably caused by a reduced segmental mobility as a consequence of the interactions of the Li+ ions with the ethylene oxide units of the polymer. Based on the free-volume theory of Cohen–Turnbull the ionic conductivity σ is correlated with the mean hole volume νh. A linear relation between log(σT 0.5) and 1/νh was observed to be valid for variations of the conductivity over several orders of magnitudes. From these plots critical hole sizes of γν*=0.65 nm3 (neat polymer) and 0.87 nm3 (polymer-salt system) were estimated. The parameters B and T0 of the Vogel–Tamman–Fulcher equation were also determined, as well as the apparent activation volume ΔVapp by pressure-dependent conductivity measurements. The cationic transference number in the polymer-salt system was determined by pulsed field gradient-nuclear magnetic resonance to be t+≈0.3.

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Positron annihilation in ionic conductivity polymers

Cited by 4 publications

References 16 publications

Local Free Volume and Structure of Polymer Gel Electrolytes on the Basis of Alternating Copolymers

Local Free Volume and Structure of Polymer Gel Electrolytes on the Basis of Alternating Copolymers

Anion exchanged polymerized ionic liquids: High free volume single ion conductors

The local free volume, glass transition, and ionic conductivity in a polymer electrolyte: A positron lifetime study

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