solid polymer electrolyte membranes based on siliconorganic backbone

7
Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone Omari Mukbaniani,* 2 Kaloyan Koynov, 3 Jimsher Aneli, 2 Tamar Tatrishvili, 1,2 Eliza Markarashvili, 1,2 Maia Chigvinadze 2 Summary: The hydrosilylation reactions of a,v–bis(trimethylsiloxy)methylhydrosiloxane with allyl butyrate and vinyltriethoxysilane catalyzed by Karstedt’s (Pt 2 [(VinSiMe 2 ) 2 O] 3 ) catalyst, platinum hydrochloric acid (0.1 M solution in THF) and platinum on carbon have been studied. In the presence of Karstedt’s catalyst the reaction order, activation energies and rate constants have been determined. The synthesized oligomers were analyzed with FTIR, 1 H, 13 C, and 29 Si NMR spectroscopy. Synthesized polysiloxanes were investigated by wide-angle X-ray scattering, gel- permeation chromatography, and DSC methods. Solid polymer electrolyte membranes have been obtained via sol-gel processes of oligomer systems doped with lithium trifluoromethylsulfonate (triflate) or lithium bis(trifluoromethylsulfonyl)imide. The dependence of ionic conductivity as a function of temperature and salt concentration has been investigated. It has been found that the electric conductivity of the polymer electrolyte membranes at room temperature changes in the range 4 10 5 –6 10 7 S/cm. Keywords: cross-linking; hydrosilylation; membranes; polymer electrolyte; polysiloxanes Introduction Since Wright [1] discovered ionic conductivity in a PEO/Na þ complex, the research and development effort have become quite active on solid polymer electrolytes (SPE), in particular, on the improve- ment of the ionic conductivity. The principal requirements for high conductivity of a SPE are the ability to solvate ions and a low glass transition temperature to afford facile ion transport. The promotion of the anioncation dissociation is desirable, because it leads to enhancement of ionic conductivity via an increase in the free ion concentration. Recognizing that the ionic conduc- tivity of polymer electrolytes is enhanced in the elastomeric amorphous phase by the segmental motion of the polymer chains, signicant research has been undertaken to develop a polymer structure having a highly exible backbone and amorphous character. To decrease the glass transition temperature, T g , of the polymer, studies have been conducted on the preparation of oligo (ethylene oxide) grafted comb-shaped and net- work solid polymers using different polymer backbones such as polyphosphazene, [2,3] polya- crylate [46] and polysiloxane. [711] Among the above mentioned polymers, poly- siloxanes are particularly promising because they can have a wide variety of substituents bound to silicones in the backbone of the alternating silicon and oxygen atoms. Polysiloxanes are superior to polyphosphazenes because of their backbone exibility, chemical stability, thermal stability, and low toxicity. [1214] A variety of organic groups can be bound to the silicon that includes ethylene oxide containing side chains. The polysiloxanes, with very low glass transi- tion temperatures, T g ¼123 C for poly(dime- thylsiloxane), and extremely high free volumes, are expected to be good hosts for Li þ transport, when polar units are introduced into the polymer backbone. Hooper et al. [15] have reported that the double - comb-type polysiloxane compounds prepared from the condensation of bis[oligo(ethylene glycol) etherpropyl]dichlorosilane showed conductivity of 4.5 10 4 S · cm 1 . The conductivity of these polymers is very close to the conductivity necessary for practical applications (10 3 S · cm 1 ). The present work is devoted to the synthesis of cross-linked polysiloxane polymer electrolytes (PE) with pendant propyl butyrate groups as internally plasticizing chains. This free-standing polysiloxane 1 Iv. Javakhishvili Tbilisi State University, I. Chavchavadze Ave. 1, 0179 Tbilisi, Georgia 2 Institute of Macromolecular Chemistry and Polymeric Materials, Iv. Javakhishvili Tbilisi State University, Georgia E-mail: [email protected] 3 Max-Planck Institute for Polymer Research, Ackermannweg 10, POBox 3148, D 55128 Mainz, Germany Macromol. Symp. 2013, 328, 38–44 DOI: 10.1002/masy.201350604 38 | Copyright ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com

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Page 1: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

Solid Polymer Electrolyte Membranes Based on

Siliconorganic Backbone

Omari Mukbaniani,*2 Kaloyan Koynov,3 Jimsher Aneli,2 Tamar Tatrishvili,1,2

Eliza Markarashvili,1,2 Maia Chigvinadze2

Summary: The hydrosilylation reactions of a,v–bis(trimethylsiloxy)methylhydrosiloxane with

allyl butyrate and vinyltriethoxysilane catalyzed by Karstedt’s (Pt2[(VinSiMe2)2O]3) catalyst,

platinum hydrochloric acid (0.1 M solution in THF) and platinum on carbon have been studied. In

the presence of Karstedt’s catalyst the reaction order, activation energies and rate constants have

been determined. The synthesized oligomers were analyzed with FTIR, 1H, 13C, and 29Si NMR

spectroscopy. Synthesized polysiloxanes were investigated by wide-angle X-ray scattering, gel-

permeation chromatography, and DSC methods. Solid polymer electrolyte membranes have been

obtained via sol-gel processes of oligomer systems doped with lithium trifluoromethylsulfonate

(triflate) or lithium bis(trifluoromethylsulfonyl)imide. The dependence of ionic conductivity as a

function of temperature and salt concentration has been investigated. It has been found that the

electric conductivity of the polymer electrolyte membranes at room temperature changes in the

range 4 � 10�5–6 � 10�7 S/cm.

Keywords: cross-linking; hydrosilylation; membranes; polymer electrolyte; polysiloxanes

Introduction

Since Wright[1] discovered ionic conductivity in aPEO/Naþ complex, the research and developmenteffort have become quite active on solid polymerelectrolytes (SPE), in particular, on the improve-ment of the ionic conductivity. The principalrequirements for high conductivity of a SPE arethe ability to solvate ions and a low glass transitiontemperature to afford facile ion transport. Thepromotion of the anion–cation dissociation isdesirable, because it leads to enhancement ofionic conductivity via an increase in the free ionconcentration. Recognizing that the ionic conduc-tivity of polymer electrolytes is enhanced in theelastomeric amorphous phase by the segmentalmotion of the polymer chains, significant researchhas been undertaken to develop a polymerstructure having a highly flexible backbone andamorphous character. To decrease the glasstransition temperature, Tg, of the polymer, studieshave been conducted on the preparation of oligo(ethylene oxide) grafted comb-shaped and net-

work solid polymers using different polymerbackbones such as polyphosphazene,[2,3] polya-crylate[4–6] and polysiloxane.[7–11]

Among the above mentioned polymers, poly-siloxanes are particularly promising because theycan have a wide variety of substituents bound tosilicones in the backbone of the alternating siliconand oxygen atoms. Polysiloxanes are superior topolyphosphazenes because of their backboneflexibility, chemical stability, thermal stability,and low toxicity.[12–14] A variety of organic groupscan be bound to the silicon that includes ethyleneoxide containing side chains.

The polysiloxanes, with very low glass transi-tion temperatures, Tg ¼ �123 �C for poly(dime-thylsiloxane), and extremely high free volumes,are expected to be good hosts for Liþ transport,when polar units are introduced into the polymerbackbone.

Hooper et al.[15] have reported that the double -comb-type polysiloxane compounds prepared fromthe condensation of bis[oligo(ethylene glycol)etherpropyl]dichlorosilane showed conductivityof 4.5 � 10�4 S · cm�1. The conductivity of thesepolymers is very close to the conductivity necessaryfor practical applications (10�3 S · cm�1).

The present work is devoted to the synthesis ofcross-linked polysiloxane polymer electrolytes (PE)with pendant propyl butyrate groups as internallyplasticizing chains. This free-standing polysiloxane

1 Iv. Javakhishvili Tbilisi State University, I. Chavchavadze Ave.1, 0179 Tbilisi, Georgia

2 Institute of Macromolecular Chemistry and Polymeric Materials,Iv. Javakhishvili Tbilisi State University, GeorgiaE-mail: [email protected]

3 Max-Planck –Institute for Polymer Research, Ackermannweg10, POBox 3148, D 55128 Mainz, Germany

Macromol. Symp. 2013, 328, 38–44 DOI: 10.1002/masy.20135060438 |

Copyright � 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com

Page 2: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

conductive material doped with lithium trifluorome-thylsulfonate (triflate) (LiSO3CF3) or lithium bis(trifluoromethylsulfonyl)imide (LiN(SO2CF3)2)shows high room temperature conductivity, arisingfrom the vigorous segmental motion of the pendantpropyl butyrate chains as well as the high flexibilityof the siloxane backbone.

Experimental Part

Materials

Polymethylhydrosiloxane (PMHS) (degree ofpolymerization, n ¼ 35) (Aldrich), platinumhydrochloric acid (Aldrich), Karstedt’s catalyst(Pt2[(VinSiMe2)2O]3) or platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (2% solu-tion in xylene) (Aldrich), Pt/C (10%) (Aldrich),allyl butyrate (Aldrich) and vinyltriethoxysilane(Aldrich) were used as received. Lithium trifluor-omethylsulfonate (triflate) and lithium bis(trifluor-omethylsulfonyl)imide were purchased fromAldrich. Toluene was dried and distilled fromsodium under atmosphere of dry nitrogen. Tetra-hydrofuran (THF) was dried over and distilledfrom K–Na alloy under an atmosphere of drynitrogen. 0.1 M solution of platinum hydrochloricacid in THFwas prepared and kept under nitrogenat low temperature.

Characterization

FTIR spectra were recorded on a Nicolet Nexus470 spectrometer with MCTB detector. 1H, 13Cand 29Si NMR spectra were recorded on a VarianMercury 300VX NMR spectrometer, using dime-thylsulphoxide and CCl4 as the solvent and aninternal standard.

Differential scanning calorimetric (DSC) mea-surements were performed on a Netzsch DSC 200F3 Maia apparatus. The heating and coolingscanning rates were 10 K/min.

Gel-permeation chromatographic studies werecarried out with the use of a Waters Model 6000Achromatograph with an R 401 differential refrac-tometer detector. The column set comprised 103

and 104 Å Ultrastyragel columns. Sample concen-tration was approximately 3% by weight intoluene and a typical injection volume for thesiloxane was 5 mL flow rate – 1.0 ml/min.Standardization of the GPC was accomplishedusing styrene or polydimethylsiloxane standardswith known molecular weight.

Wide-angleX-ray analyses were performed on aDRON-2 (Burevestnik, Saint Petersburg, Russia)

instrument. CuKa radiationwas used with graphiticmonochromator; the angular velocity of the motorwas v � 2�/min.

The content of active �Si-H groups in oligom-ers was calculated according to literature data.[16]

Hydrosilylation Reaction of PMHS withAllyl butyrate in the Presence ofKarstedt’s Catalyst

PMHS 0.7560 g, (0.3342 mmol) were transferredinto a 100 mL flask under nitrogen using standardSchlenk techniques. High vacuum was applied tothe flask for half an hour before the addition ofallyl butyrate (1.4993 g, 0.01169 mol). The mix-ture was then dissolved in 3 mL of toluene, and0.1 M solution of platinum hydrochloric acid intetrahydrofuran (5�9 · 10�5 g per 1.0 g of startingsubstance) was introduced. The homogeneousmixture was degassed and placed into an oil bath,which was previously set to 60 �C and reactioncontinued at 60 �C. The reaction was controlled bythe decrease of intensity of active �Si-H groups.

Subsequently, 0.1% activated carbon wasadded and refluxed for 12 h for deactivation ofcatalysts. All volatiles were removed by rotaryevaporation and the polymer was precipitated atleast three times into pentane to remove sideproducts. Finally, all volatiles were removed undervacuum and further evacuated under high vacuumfor 24 h to isolate the colorless viscous polymer,1.89 g (93%).

The hydrosilylation reactions of PMHS withallyl butyrate and vinyltriethoxysilane in thepresence of other catalysts were carried out usingan analogous method as that described above.

General Procedure for Preparation ofCross-Linked Polymer Electrolytes

The 0.75 g of the base compound II was dissolvedin 4 mL of dry THF and thoroughly mixed for halfan hour before the addition of the catalytic amountof acid (one drop of 0.1 N HCl solution in ethylalcohol) to initiate the cross-linking process. Afterstirring for another 3 h the required amount oflithium triflate from the previously prepared stocksolution in THF was added to the mixture andfurther stirred for 1 h. The mixture was thenpoured onto a Teflon mould with a diameter of4 cm and the solvent was allowed to evaporateslowly overnight. Finally, the membrane was dried

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Page 3: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

in an oven at 70 �C for 3 days and at 100 �C for 1 h.Homogeneous and transparent films with averagethickness of 200 mm were obtained in this way.These films were insoluble in all solvents, onlyswollen in THF.

Ac Impedance Measurements

The total ionic conductivity of samples wasdetermined by locating an electrolyte disk be-tween two 10 mm diameter brass electrodes. Theelectrode/electrolyte assembly was secured in asuitable constant volume support which allowedextremely reproducible measurements of conduc-tivity to be obtained between repeated heating–cooling cycles. The cell support was located in anoven and the sample temperature was measuredusing a thermocouple positioned close to theelectrolyte disk. The bulk conductivities of electro-lytes were obtained during a heating cycle usingthe impedance technique (Impedance meter BM507–TESLA for frequencies 50 Hz–500 kHz) overa temperature range between 20 and 100 �C.

Results and Discussion

Methylsiloxane polymers with propyl butyrate andethoxy side groups have been synthesized viahydrosilylation reaction of a,v-bis(trimethylsi-loxy)methylhydrosiloxane with allyl butyrate andvinyltriethoxysilane in the presence of platinumcatalysts (platinum hydrochloric acid, [(Pt2[(Vin-SiMe2)2O]3, and platinum on carbon) in concen-trated solution of dry toluene.

Preliminary heating of initial compounds in thetemperature range of 50–80 �C in the presence ofcatalysts showed that in these conditions polymer-ization of allyl butyrate and destruction of siloxane

backbone do not take place. No changes in theNMR and FTIR spectra of initial compounds werefound.

The above mentioned reactions were carriedout without solvent at 50 �C temperature. It wasfound that the reactions proceeded vigorously(especially in case of platinum hydrochloric acidand Karstedt’s catalyst) and at initial stages ofconversion of�Si-H bonds (�25%) gelation takesplace via intermolecular dehydrocoupling reac-tion. To prevent gelation and to investigate thekinetic parameters of the reaction we have carriedout hydrosilylation in dry toluene (C � 0.06301mole/l).

In general, hydrosilylation of PMHS with allylbutyrate proceeds according to the followingScheme 1. Where: [(a) þ (b) þ (c) þ (d)](x) ¼m�35; Cat - Karstedt’s catalyst (Pt2[(VinSi-Me2)2O]3–60 �C (I1), 70 �C (I2) and 80 �C (I3);H2PtCl6–80 �C (I4), Pt/C – 80 �C (I5) (ratio m:n ¼ 1:35, p ¼ d ¼ 0). Cat - Karstedt’s, where[(a) þ (b) þ (c) þ (d)](x) ¼ m�35; 70 �C (II)(ratio m:n:p ¼ 1:28:7).

The synthesized oligomers are vitreous liquidproducts, which are well soluble in organicsolvents with specific viscosity hsp � 0.07–0.10.Structures and compositions of the oligomers weredetermined by elemental and functional analyses,FTIR, 1H, 13C and 29Si NMR spectral data.Synthesized polysiloxanes were characterized bywide-angle X-ray scattering analyses. Some char-acteristics of the hydrosilylation reaction and thesynthesized oligomers are presented in Table 1.

In the FTIR spectra of oligomers I3 and II onecan observe absorption bands characteristic ofasymmetric valence oscillation of linear �Si-O-Si� bonds at 1018–1033 cm�1. In the spectra,absorption bands at 1096 cm�1 and 1180–

Scheme 1.

Hydrosilylation reaction of PMHS with allyl butyrate and vinyltriethoxysilane.

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Page 4: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

1187 cm�1, characteristic of asymmetric valenceoscillation of �Si-O-Si� and C-OC bonds areobserved. One can observe absorption bands at1265, 1735 and 2700–3100 cm�1, characteristic ofvalence oscillation of �Si-C�, C¼O and �C-Hbonds accordingly. In the FTIR spectra there is anabsorption band characteristic for un-reacted �Si-H bonds at 2160 cm�1.

The 1H, 13C and 29Si NMR spectra of all thesynthesized oligomers were analyzed. As anexample, Figure 1 includes the 1H NMR spectraof oligomers I3 and II (fragment �Si-C1H2-CH

22-

CH32-O-C4O-CH5

2-CH62-C

7H3). One can observesinglet signals with chemical shift d ¼ 0.1–0.2 ppmcharacteristic for protons in �Si-Me and -SiMe3groups; multiplet signals with chemical shifts

Table 1.Some characteristic data of the PMHS hydrosilylation reaction with allyl butyrate and the resulting oligomers.

Oligo merNo.

Yield, % Reactiontemperature, �C

Ratio ofinitial

compounds

�Si-H %,conversion

Mn � 10�3 Mw � 10�3 ðPÞ hsp d1, A Tg,

�C

I1 86 60 1:35 62 – 0.08 7.39 –I2 84 70 1:35 71 – 0.08 – –I3 85 80 1:35 80 13.6 0.09 – �82

25.1 (2.58)I4 88 80 1:35 79 – 0.10 7.42 –I5 79 80 1:35 63 – 0.07 – –II 84 80 1:28:7 84 9.72 0.10 – �79

47.8 (3.51)

In 1% toluene solution, at 25 �C.

Figure 1.1H NMR spectra of oligomer I3(a) and oligomer II (b).

Macromol. Symp. 2013, 328, 38–44 | 41

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Page 5: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

centred at d � 0.55, d � 0.9, d � 1.15 andd � 1.75 ppm characteristic of methyl and methy-lene protons in �Si-C1H2-, C

7H3, -CHCH3, C6H2

and C2H2 groups respectively.Multiplet signals at d ¼ 2.3, 3.9 ppm corre-

spond to methylene protons in C5H2 and C3H2

groups (oligomer II). Hydrosilylation mainlyproceeds according to the anti-Markovnikov rule.The multiplet signal with d ¼ 1.6 corresponds tomethin protons in ¼CH-CH3 group.

In the 13C NMR spectra of polymer I3 and II(results not shown here), one can see a singletsignal with chemical shift d � �0.2 ppm charac-teristic of carbon core in �Si-CH3 group. Addi-tional signals with chemical shifts at d � 14.6,19.27, 23.12, 37.02 and 67.17 ppm correspondingto C2, C7, C6, C5, C3 carbon atoms can be observed,together with a signal at 174.5 ppm correspondingto carbon atoms in carbonyl groups.

In the 29Si NMR spectra of oligomers I3 and II(results not shown here) one can see a pure signalwith chemical shift d ¼ �22 ppm corresponding tothe presence of RR’SiO (D) units. On the otherhand, two signals corresponding to the presence ofDOM and T units at �55 and �65 ppm (foroligomer II) are also observed.

The synthesized oligomers were studied bymeans of GPC. Oligomers I3 and II exhibit a tri-and tetramodal molecular weight distribution,giving average molecular weights in the range:Mn � 0.972–1.36 � 104 (g/mol), Mw ¼ 2.51–4.78 � 104, and a polydispersity of D ¼ 2.58–3.51.

Here it is obvious that the average molecularweights of the synthesized oligomers exceedseveral times the theoretical values of themolecular weights calculated in case of fullhydrosilylation. It indicates that during inter-molecular hydrosilylation reaction branching pro-cesses on active �Si-H groups also takes place,which is in agreement with literature data.[17]

Hence, the obtained oligomers are various linkedbranched systems.

During the hydrosilylation reaction, a decreaseof active �Si-H groups’ concentration with timewas observed. The hydrosilylation reaction wasperformed in dry toluene solution (C �6.301 · 10�2 mole/l). As it is evident from Table 1not all active �Si-H groups participate in thehydrosilylation reaction. Figure 2 shows thevariation of the concentration of active �Si-Hgroups with time during the hydrosilylationreaction of PMHS with allyl butyrate in thepresence of Karstedt’s catalyst at different reactiontemperatures. The ratio of initial compounds was

of m:n ¼ 1:35 (see Scheme 1). From Figure 2 it isevident that the depth of hydrosilylation reactionrises with the increase of temperature.

From the dependence of the inverse concentra-tion of �Si-H groups with time during hydro-silylation reaction of PMHS with allyl butyrate itwas found that the reaction is of second order; thereaction rate constants at various temperatureswere determined, yielding: k60 �C � 0.5543,k70 �C � 1.00 and k80 �C � 2.05030 l/mole · min.From the dependence of the hydrosilylationreaction rate constants’ logarithm on the recipro-cal temperature the activation energy of hydro-silylation reaction was calculated, which is equal toEact � 64.36 kJ/mole.

The wide angle X-ray scattering diffractogramsof the investigaged polymers showed two broaddiffraction maximums at 2u� � 11.75–12.00� and2u� � 20.50–20.75�. Results suggest that thepolymers are represented as one phase amorphoussystems. The first intensity maximum correspondsto interchain distances in the range d1 ¼ 7.39–7.42Å and the second one at 4.35–4.41 Å whichcharacterized intra- and interchain atomic inter-actions respectively.[18]

Oligomers I3 and II were doped with two typesof lithium salts: triflat (CF3SO3Li) - S1 and(trifluoromethanesulfonyl)imide (CF3SO2N(Li)SO2CF3) – S2 at two concentrations of these salts(10 and 20 wt %).

AC impedance measurements were employedto investigate the variation of conductivity withtemperature for all the obtained electrolytes.Figure 3 and 4 illustrate the Arrhenius plots ofthe dependence of electrical conductivity of PEbased on I3 and II with salts S1 and S2 at differentcontents.

Figure 2.

Dependence of changes of active�Si-H groups concentration

on the time during hydrosilylation reactions of PMHS with

allyl butyrate at 60 �C (1), 70 �C (2) and 80 �C (3) (- Karstedt’s

catalyst).

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Page 6: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

The curves in Figure 3 and 4 (see also data ofTable 2) show that electrolytes on the basis ofpolymer I3 containing salts S1 and S2 arecharacterized with relatively high conductivity incomparison to the electrolytes on the basis ofpolymer II. Probably the first polymer with triflatcreates the friable structure significantly abetting

ion transfer through the polymer matrix. On theother hand, ions on the basis of salt triflatapparently have higher mobility to some extentthan second ones. The increase of the amount ofpendant groups -C3H6-O-COC3H7 seems toenhance the conductivity of the electrolyte.

In general, the temperature dependencies ofconductivity of the investigated membranes can bedescribed by an equation close to the well knownVTF one.[19] It must be noted that the conductivityof the electrolyte membrane I3S1, at salt concen-tration 20 wt% is characterized with higherconductivity values than those for the onecontaining 10 wt% of the same salt. However,the conductivity of the membrane IIS2 containing20 wt% S2 is lower than that of the one containing10 wt%of the same salt. This phenomenonmay beexplained by: 1) formation of ion pairs on the basisof molecules of salt S2 which are characterized withrelatively high interactions (usually this formationtakes place at higher concentrations of the salt inthe electrolytes[19]), 2) increase of material densityand consequently decrease of charge transfer inthe polymer matrix due to the higher concentra-tion of S2 salt having bulkier molecules than S1.Obviously, when considering the factors effective-ly influencing the charge transfer in polymerelectrolytes it is necessary to take into accountvarious aspects such as structure peculiarities,localization of the salt molecules in the polymermatrix, viscosity and thermal properties. Theviscosity in particular is a factor significantlyaffecting the conductivity of polymer electrolytes.Experimentally it is established that viscosity (h)and conductivity (s) are in inversely proportionaldependence and that their product is constant(h � s ¼ const). Besides, ion conductivity at agiven temperature (T) is proportional to the sumof the products of the following parameters:number of free ions (ni), charge carrier ions (qi)and ion mobility (mi):

[20] (s (T) ¼ S ni qi mi).The voltamograms of each electrolyte based on

a a different type and content of salt are includedin Figure 5.

As can be seen fromFigure 5 the saturation of theelectrical current depends significantly on thecomposition of the electrolytes. The length of theinitial linear part (up to bend) of the electricalcurrent is longer the higher is the conductivity.Deviations from the linear increase of intensity withvoltage are partially related to charge-phononinteractions that are enhanced with increasing ionenergy giving rise to a decrease of the electrolytesconductivity.[21] Phonon-charge carriers interactions

2.6 2.8 3.0 3.2 3.4-6

-5

-4

-3 B C D E

lgσ,

S/cm

1000/T,1/K

Figure 3.

Arrhenius plot of the dependence of electrical conductivity of

PE based on I3 with salts S1 at concentrations 20 wt % (B) and

10 wt % (C) and with S2 at concentrations 10 wt % (D) and

20 wt% (E).

2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5-8

-6

-4

B C

lgσ,

S/cm

1000/T,1/K

Figure 4.

Arrhenius plot of the dependence of electrical conductivity of

PE based on II with salt S2 at concentrations 10 wt % (B) and

20 wt % (C).

Table 2.Conductivity of polyelectrolytes on the basis of polymersof type I3 and II containing the salts S1 and S2

Polymer Salt Content ofsalt, wt %

s (30 �C),S · cm�1

s (90 �C),S · cm�1

I3 S1 10 6.3 � 10�6 4.2 � 10�4

I3 S1 20 2.1 � 10�5 6.1 � 10�4

I3 S2 10 3.2 � 10�6 1.6 � 10�4

I3 S2 20 2.1 � 10�6 6.0 � 10�5

II S2 10 8.1 � 10�7 8.0 � 10�5

II S2 20 3.2 � 10�8 5.1 � 10�5

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Page 7: Solid Polymer Electrolyte Membranes Based on Siliconorganic Backbone

would be promoted for higher densities of thepolymer matrix density.

Conclusion

The synthesis of oligomers via hydrosilylationreaction of methylhydrosiloxane with allyl buty-rate and vinyltriethoxysilane methylsiloxane withelectro donor propyl butyrate and triethoxysilylfragments in the side chain has been carried out.The oligomers were linked via sol-gel processesand lithium salts were added to obtain solidpolymer electrolyte membranes.

The conductivity of themembranes in the range30–90 �C can be described with an equation closeto VTF type. The membranes containing triflattype salt are characterized with higher conductivi-ty in the range of temperatures investigated withrespect to electrolytes containing (trifluorome-thylsulfonyl) imide presumably due to the highermobility of the former salt ions.

Acknowledgement: The financial support of theGeorgian National Science Foundation Grant #STCU5055 is gratefully acknowledged.

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0 2 4 6 8 100

20

40

60

80

100

120 B C D E F G

I,m

cA

U,V

Figure 5.

The voltamograms of the electrolytes based on I3S1 with

contents of S1: 10 wt % (F) and 20 wt % (G); I3S2 with contents

of S2 : 10 wt % (E) and 20 wt % (D); IIS2 at concentrations of S210 wt % (C) and 20 wt % (B).

Macromol. Symp. 2013, 328, 38–4444 |

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