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Anion dynamics and conductivity in glassy polyelectrolytes - a two-dimensional solid state NMR study
SOLID STATE ELSEVlER
Solid State Ionics 68 ( 1994) 151-158
IOIIICS
Anion dynamics and conductivity in glassy polyelectrolytes a two-dimensional solid state N M R study R . - R . R i e t z , K . S c h m i d t - R o h r , W . H . M e y e r 1, H . W . S p i e s s , G . W e g n e r Max-Planck-lnstitutefor PolymerResearch, P.O. Box 3148, D-55021 Mainz, Germany Received 29 April 1993; accepted for publication 20 January 1994
Abstract
For the first time, the dynamics of the anions of ionically conducting amorphous polyelectrolytes have been investigated by applying one- and two-dimensional solid state ]3C-NMR techniques. The glass transition in cationic polyelectrolytes of the type "ionenes" is characterized by the softening of a network formed by N+-cations which are linked by organic segments. However,
the counterions are already mobile below the glass transition. About 40 K below Ts, the anion dynamics are found to be spatially isotropic on the NMR timescale, which is in good agreement with results obtained by dielectric spectroscopy. The ionic conductivity in the glassy state can be described as thermally activated anion transport. Its high activation energy indicates a cooperative character of the anion motion.
1. Introduction
Ionenes (I) are polyelectrolytes with N+-cations as part of their polymer chain repeat unit, with low molecular weight anions to balance the coulombic charges, e.g. " I - 1 0 - M e - S C N " , R I = R 2 = (CH2)1o, X - = S C N - [1].
~
CH3
CH3
q
N+--R1--N+--R2 4
(I)
Ionenes with large organic main chain or side chain segments exhibit low charge densities and form amorphous solids [ 2 ]. The solid state properties of ionene glasses have been investigated recently in detail by thermoanalytical, dielectric and solid state ~# Corresponding author.
N M R techiques [ 3-7 ]. These results characterize the glass transition in ionenes as the softening of a network formed by the N+-cations. The organic chain segments linking the cationic centers are mobile already in the glassy state. Their dynamics can be described as motion between fixed ends. The anions give rise to an ionic conductivity already at low temperatures in the glassy state of ionenes. The objective of this study is to characterize the ionic conductivity in ionenes below their glass transition temperature. Dielectric spectroscopy reveals that the frequency and temperature dependence of the ionic conductivity can be described by a model proposed by Funke [ 8 ] modified for the low frequency limit [9 ]. The motion of the anions can be described as thermally activated hopping in the cation network and in the matrix of the organic segments. These results are in good agreement with results obtained by one- and two-dimensional solid-state 13C-NMR experiments in which the diffusional motion of S13CNanions have been probed.
0167-2738/94/$07.00 © 1994 Elsevier ScienceB.V. All rights reserved SSDIO167-2738(94)OOOI7-M
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R.-R. Rietz et aL / Solid State Ionics 68 (1994) 151-158
2. Experimental The details of the synthesis of ionenes have been reported elsewhere [ 10 ]. Their glass transition temperature Tg, the specific heat change at Tg and the decomposition temperature Tdec have been determined with heating rates 20 K / m i n with a Mettler DSC-30 and Mettler TGA 50 respectively. The corresponding data for 1-10-Me-SCN are: Tg= 19°C, Acp=0.22 J / (g.K), Tde~= 225 °C. The experimental details of the dielectric investigations have likewise been described elsewhere [9]. The static 13C_NMR spectra have been acquired on a Bruker MSL 300 spectrometer. With a field strength of 7.05 T the Larmor frequency for 13C was 2rc-75.47 MHz. The temperature of the samples was controlled via a thermostated nitrogen gas flow. The polyelectrolyte samples were isotopically enriched with S 13CN ( 13C_concentratio n > 99%).
3. NMR background The solid state 13C-NMR spectra are dominated by the magnetic shielding of the nuclei by the surrounding electrons (chemical shift ). Due to the substantial average distance between the anions (about 1.2 nm) the 13C-13C dipole-dipole coupling is negligible for I-10-Me-S13CN despite the isotopic enrichment. The chemical-shift tensor a (CST) is anisotropic in the solid state. The anisotropy of the chemical shift results in a dependence of the resonance frequency on the orientation of the molecular segment. Therefore, the information about rotational motions is provided by angular-dependent N M R frequencies [ 11 ] : co=coL + ½ J ( 3 C o s Z O - - I - - ~ l s i n 2 O c o s 2 ~ )
,
(1)
coL is the Larmor frequency, J describes the strength of the anisotropic coupling, and r/is the asymmetry parameter describing the deviation of the anisotropic coupling from axial symmetry. The angles 0 and q~are the polar angles of the external magnetic field in the principal axis system of the coupling tensor. For the linear S13CN ion the chemical shift tensor is axially symmetric (~/= 0 ) around its long axis. In powder samples the spectra for all orientations are added to yield the powder lineshape. In the presence of rapid motions with correlation times below 1
ms the N M R lineshape will change [ 12 ]. Slower motions with correlation times re> 1 ms can be studied by 2D exchange N M R [ 13,14 ]. The intensity in a two-dimensional spectrum is the joint probability density S(Coe, cod; tm) of finding a molecular unit with a frequency coe before the mixing t i m e tm and with a frequency cod afterwards. For the S~3CN ion motions which change the orientation of the long axis of the ion are probed. The case of no reorientation manifests itself in a diagonal spectrum. Off-diagonal intensity (coe¢ cod) indicates reorientational processes during tm. A sequence of 2D spectra at a given temperature with mixing times in the range from 1 ms to several seconds is essential to obtain information about the dynamic evolution [ 15,16 ]. Estimates of correlationtime scales are possible without the assumption of a model just by measuring the ratio of off-diagonal intensity to diagonal intensity. A detailed analysis including a distribution of correlation times is based on the assumption of a motional model. For example, amorphous materials often show broad reorientational-angle distributions which have been described successfully with the isotropic rotational diffusion model [ 15-17 ]. This model involves small angular steps and yields a reorientation-angle distribution which depends only on the ratio of mixing time to correlation time tm/Zc. Often, the spectra cannot be described by a single correlation time zc, but with a distribution of correlation times. The log-Gaussian distribution with z0=exp(ln zc) as its center is applied here to the amorphous system I-10-Me-S~aCN: G(ln z) = (27c0"2 ) -X/2exp[ - (ln r - I n ~'0)2/20 "2 ]
(2) with LJo= log [exp (2a) ] as the total width in decades and ZJl/2 = 1.774.A~ as the full width at half height in decades.
4. Dielectric properties Like all aliphatic ionenes, the ionene I - 10-Me-SCN displays two major effects [ 6 ]: firstly, a conductivity contribution called 13-relaxation, and secondly a relaxation process called y-relaxation (Fig. 1 ). The latter process can be observed at lower temperatures. It exhibits a maximum in ~2 that shifts to higher fre-
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
z,oNq2x~ B = 6------~- '
-7-8-9-10.
ogs _
5 4
_~ -11-12. -13 4
5
~ 6 7 IO00/T [K-1]
0_1 8
Fig. 1. Arrhenius plot of the real part of the complexconductivity of I-10-Me-SCN with frequency as parameter. The "/-relaxation shifts to higher temperatures with increasingfrequency.The critical frequencyof 0.1 Hz is at 225 K. quencies with increasing temperature. The two processes can be differentiated by the following equations [ 9 ]:
1
t2
_
~o
p
exp(-Adc/kT) .
153
(8) (9)
The temperature dependence of the dc conductivity, and the critical frequency are described by Eqs. ( 7 ) ( 9 ) . N ~ V is the density of the mobile ions, q is the charge, Xo is the hopping distance, k is the Boltzmann constant, and Vo is an oscillatory frequency of the anion. Ad~ is the value for the activation energy of the dc conductivity. The dc activation energy of I - 10-MeSCN is around 106 kJ/mol, and the preexponential factor of the critical frequency is 6 × 1013 Hz, indicating a cooperative process. The critical frequency at Tg is 59 kHz, and the critical temperature for a hopping rate of 1 kHz is 267 K. For a detailed discussion of the anion conductivity see eslewhere [9,18].
~"(o9) = e"(o)) + G'el.x(o)) ,
(3)
N M R results
a(0) ( o)P-- 1~ " - o9-1+ e~= ~o o)f ,1'
(4)
~;;lax=Im 1 + (--:l~Z) ci "
(5)
Fig. 2 shows the static 13C N M R spectra of I 10-Me-S13CN (Tg=292 K) for several temperatures. The aliphatic chain segments have a stronger dipole-dipole coupling with the protons than the L3Cnuclei in 513CN - . Therefore, before detection, their signal can be suppressed with a waiting time during which their intensity disappears (gated decoupling). At 205 K the spectrum appears to be a rigid Pake pattern. A change of the lineshape indicating the onset of motion is observed at 225 K. At 260 K/275 K there is already reorientation with isotropic parts on the time scale of the 1D N M R experiment. However, the glass transition of 1-10-Me-SCN is 292 K, a temperature where the motional rate of the counterions is in the range of 0.1 MHz. In the N M R experiment rotational motion is observed. Hence, it is necessary to extract the activation energy or the correlation times, respectively, to compare the reorientational motion observed by N M R with the conductivity data obtained by dielectric spectroscopy. According to the dielectric investigations the correlation time at 250 K should be in the range of 10 ms. Therefore, static L3C 2D exchange experiments are performed between 215 K and 260 K with various mixing times (Figs. 3 and 4). In Fig. 3, 2D spectra with a mixing time of 50 ms
The dc conductivity is characterized with a ( 0 ) ; Co is the vacuum permittivity. At the critical frequency o)s, the dispersion of the conductivity begins. The parameter p describes the slope of that dispersion in the log frequency-log conductivity-plot. Eq. (5) is the well-known Cole-Cole function. The parameter determines the width of the symmetric distribution of the mean relaxation time r, and Ae is the relaxation strength. With o-*(to)=ioJ%e*(o)) Eq. (4) can be written as
a( oJ ) = a ( O) +a(O).o~p/o~f.
(4a)
The 7-relaxation of all ionenes exhibits an Arrheniuslike behavior (Eq. ( 6 ) ) . Especially, the activation energy of 1-10-Me-SCN is 38 k J / m o l with a preexponential factor of 3 × 10- ~5 s. z = zoexp ( E a / k T ) , B a' (0, T) = ~ e x p ( - A d ¢ / k T
(6) ) ,
(7)
154
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
Fig. 2. Static ~3C-NMR spectra of I - 10-Me-S ~3CN ( Tg = 292 K ). The spectral range shown for each individual plot is 400 ppm.
and corresponding simulations with the isotropic rotational diffusion model for several temperatures are shown. The off-diagonal intensity rises with increasing temperature and decreasing correlation time. Signals are found in the whole frequency plane and exhibit no relevant structure. Hence, reorientations about all angles are allowed. At 250 K, the dynamics are already spatially isotropic. The extracted activation energy is 107 kJ/mol+_ 6 kJ/mol and the preexponential factor is 2 × 1024 Hz ( + 1 decade), which is in remarkable agreement with the dielectric resuits. It should be noted that the NMR deals with a tensor of the second rank in contrast to the dielectric spectroscopy, which probes the dynamical processes with the reorientation of the dipole moment (which is a tensor of the first rank), thus for small step diffusion 3 (Zdielecnc) = (ZNMR) [ 19 ]. The diffusive character of the dynamics of the counterions and their unusually high activation energy imply distinct cooperativity of the anion mo-
tion. It is comparable with a glass transition process. Correspondingly, there must be a transition temperature which is 205 K according to the NMR experiment. At this temperature almost a rigid limit Puke spectrum is observed. The simulated spectra, however, show some deviations from the experimental spectra. The reason is an axial reorientation of the rhodanide anion in the domain of microseconds which affects the diagonal spectrum. We tried to simulate such a behavior by superimposing powder patterns with various asymmetry parameters ~/. Because there is no off-diagonal intensity at tm= 200 ms at low temperatures, 13C spin diffusion can be excluded as a relevant exchange mechanism in our spectra. As mentioned above the spectrum at 215 K is not a pure Puke spectrum. Its intensity is increased as compared to a completely rigid pattern and its width increases with mixing time (Fig. 5). Small angle librational motions could explain this observation. For an evaluation of their angular amplitudes some spectra are simulated under the assumption of slow smallangle librational motions. The spectrum with a mixing time of 1 ms is the starting point for the spectrum with a mixing time of 20 ms. Longer mixing times do not lead to further widening. These small-angle librational motions may be coupled to the polymer chain motions in the glassy state, which have been described as trans-gauche isomerizations, and which were assigned as y-relaxation on the basis of dielectric experiments [4 ]. Similar reorientations are observed in other polymer systems as well (e.g. polyethylene) [ 20 ]. In the same manner as for the simulation of the diffusive motion a superposition of powder patterns with different ~/values was necessary also in this case, because the librations have correlation times in the range of milli- and microseconds, so that the diagonal spectrum is affected. Investigations at lower temperatures would be necessary to find a rigid-limit Puke pattern. The observed small-angle librational motion is slow on the time scale of the 1D NMR experiment. In summary, the axially symmetrical rhodanide anion performs small angle librational motions at 215 K with an angular amplitude of about 10 ° and an average correlation time of approximately 3 ms.
R.-R. Rietz et al. / Solid State Ionics 68 (I 994) 151-158
155
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Fig. 3. Temperature dependence of the static l aC-2D-NMR exchange spectra for the S13CN-counterion in I - 1 0 - M e - S C N at 50 ms mixing time. The width of the (log-) Gaussian distribution of ( z c ) is 3 decades, the spectral width of the plots is 400 ppm (frequency axes; vertical: to2, horizontal: to1 ).
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R.-R. Rietz et al. / S o l i d State lonics 68 (1994) 151-158
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Fig. 4. Static ~aC-2D-NMR exchange spectra for the S13CN-counterion in I- 10-Me-SCN at 250 K for different mixing times. The spectral width of the plots is 400 ppm (frequency axes; vertical: 092, horizontal: ogt ). 6. Conclusions The dynamics o f S C N counterions of the ionically conducting amorphous polyelectrolyte I- 1 0 - M e - S C N have been investigated by applying one- and two-dimensional 13C-NMR techniques. About 40 K below Tg (292 K ) , the anion dynamics are found to be fast on the N M R timescale and spatially isotropic in nature. The activation energy for the anion m o t i o n has
been found to be about 107 k J / m o l and the preexponential factor is about 1024 Hz. These results are in g o o d agreement with those obtained by dielectric spectroscopy. The relatively high activation energy indicates a cooperative character of the anion motion. Future experiments are necessary to characterize the influence of anion geometry and polyelectrolyte chain rigidity on the anion transport.
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R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
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Fig. 5. Pake spectra of the S13CN counterions in I-10-Me-SL3CN demonstrating small angle librations.
158 7.
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
Acknowledgement This work has been financially supported by the
Deutsche Forschungsgemeinschaft (Sonderfors c h u n g s b e r e i c h 262, p r o j e c t s S- 10, D - 10).
References [ 1 ] A. Rembaum, J. Macromol. Sci. Chem. 3 (1969) 87. [2] F. Kremer, L. Dominquez, W.H. Meyer and G. Wegner, Polymer 30 (1989) 2023. [3] H.-U. Simmrock, A. Mathy, L. Dominquez, W.H. Meyer and G. Wegner, Adv. Mat. Angew. Chem. 101 (1989) 1148. [4] D. Schaefer, R.R. Rietz, W.H. Meyer and H.W. Spiess, Ber. Bunsenges. Physik. Chem. 95 ( 1991 ) 1071. [5] W.H. Meyer, J. Pecherz, A. Mathy and G. Wegner, Adv. Mater. 3 (1991) 153. [6] W.H. Meyer, R.R. Rietz, D. Schaefer and F. Kremer, Electrochim. Acta 37 (1992) 1491. [7]R.R. Rietz, D. Schaefer, W.H. Meyer and H.W. Spiess, Electrochim. Acta 37 (1992) 1657.
[8] K. Funke, Solid State Ionics 18/19 (1986) 183; Mat. Res. Soc. Symp. Proc. 125 (1989)43. [ 9 ] R.-R. Rietz and W.H. Meyer, Polymers Adv. Tech. 4 ( 1993 ) 164. [ 10] L. Dominiquez, W.H. Meyer and G. Wegner, Makromol. Chem. Rapid Commun. 8 (1987) 151. [ 11 ] M. Mehring, Principles of High Resolution NMR in Solids (Springer, Berlin, 1983). [ 12] H.W. Spiess, in: NMR-Basic Principles and Progress, Vol. 15 (Springer, Berlin, 1978 ). [ 13 ] J. Jeener, B.H. Meier, P. Bachmann and R.R. Ernst, J. Chem. Phys. 71 (1979) 4546. [ 14] A. Hagemeyer, K. Schmidt-Rohr and H.W. Spiess, Adv. Magn. Reson. 13 (1989) 85. [ 15 ] S. Wefing and H.W. Spiess, J. Chem. Phys. 89 ( 1988 ) 1219, 1234. [16] S. Kaufmann, S. Wefing, D. Schaefer and H.W. Spiess, J. Chem. Phys. 93 (1990) 197. [ 17 ] D. Schaefer, H.W. Spiess, U.W. Suter and W.W. Fleming, Macromol. 23 (1990) 3431. [ 18] R.-R. Rietz, W.H. Meyer, F. Kremer and G. Wegner, to be published. [19] H. Sillescu, J. Chem. Phys. 54 (1971) 2110. [20] D. Hentschel, H. Sillescu and H.W. Spiess, Polymer 28 (1984) 1078.
Solid State Ionics 68 ( 1994) 151-158
IOIIICS
Anion dynamics and conductivity in glassy polyelectrolytes a two-dimensional solid state N M R study R . - R . R i e t z , K . S c h m i d t - R o h r , W . H . M e y e r 1, H . W . S p i e s s , G . W e g n e r Max-Planck-lnstitutefor PolymerResearch, P.O. Box 3148, D-55021 Mainz, Germany Received 29 April 1993; accepted for publication 20 January 1994
Abstract
For the first time, the dynamics of the anions of ionically conducting amorphous polyelectrolytes have been investigated by applying one- and two-dimensional solid state ]3C-NMR techniques. The glass transition in cationic polyelectrolytes of the type "ionenes" is characterized by the softening of a network formed by N+-cations which are linked by organic segments. However,
the counterions are already mobile below the glass transition. About 40 K below Ts, the anion dynamics are found to be spatially isotropic on the NMR timescale, which is in good agreement with results obtained by dielectric spectroscopy. The ionic conductivity in the glassy state can be described as thermally activated anion transport. Its high activation energy indicates a cooperative character of the anion motion.
1. Introduction
Ionenes (I) are polyelectrolytes with N+-cations as part of their polymer chain repeat unit, with low molecular weight anions to balance the coulombic charges, e.g. " I - 1 0 - M e - S C N " , R I = R 2 = (CH2)1o, X - = S C N - [1].
~
CH3
CH3
q
N+--R1--N+--R2 4
(I)
Ionenes with large organic main chain or side chain segments exhibit low charge densities and form amorphous solids [ 2 ]. The solid state properties of ionene glasses have been investigated recently in detail by thermoanalytical, dielectric and solid state ~# Corresponding author.
N M R techiques [ 3-7 ]. These results characterize the glass transition in ionenes as the softening of a network formed by the N+-cations. The organic chain segments linking the cationic centers are mobile already in the glassy state. Their dynamics can be described as motion between fixed ends. The anions give rise to an ionic conductivity already at low temperatures in the glassy state of ionenes. The objective of this study is to characterize the ionic conductivity in ionenes below their glass transition temperature. Dielectric spectroscopy reveals that the frequency and temperature dependence of the ionic conductivity can be described by a model proposed by Funke [ 8 ] modified for the low frequency limit [9 ]. The motion of the anions can be described as thermally activated hopping in the cation network and in the matrix of the organic segments. These results are in good agreement with results obtained by one- and two-dimensional solid-state 13C-NMR experiments in which the diffusional motion of S13CNanions have been probed.
0167-2738/94/$07.00 © 1994 Elsevier ScienceB.V. All rights reserved SSDIO167-2738(94)OOOI7-M
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R.-R. Rietz et aL / Solid State Ionics 68 (1994) 151-158
2. Experimental The details of the synthesis of ionenes have been reported elsewhere [ 10 ]. Their glass transition temperature Tg, the specific heat change at Tg and the decomposition temperature Tdec have been determined with heating rates 20 K / m i n with a Mettler DSC-30 and Mettler TGA 50 respectively. The corresponding data for 1-10-Me-SCN are: Tg= 19°C, Acp=0.22 J / (g.K), Tde~= 225 °C. The experimental details of the dielectric investigations have likewise been described elsewhere [9]. The static 13C_NMR spectra have been acquired on a Bruker MSL 300 spectrometer. With a field strength of 7.05 T the Larmor frequency for 13C was 2rc-75.47 MHz. The temperature of the samples was controlled via a thermostated nitrogen gas flow. The polyelectrolyte samples were isotopically enriched with S 13CN ( 13C_concentratio n > 99%).
3. NMR background The solid state 13C-NMR spectra are dominated by the magnetic shielding of the nuclei by the surrounding electrons (chemical shift ). Due to the substantial average distance between the anions (about 1.2 nm) the 13C-13C dipole-dipole coupling is negligible for I-10-Me-S13CN despite the isotopic enrichment. The chemical-shift tensor a (CST) is anisotropic in the solid state. The anisotropy of the chemical shift results in a dependence of the resonance frequency on the orientation of the molecular segment. Therefore, the information about rotational motions is provided by angular-dependent N M R frequencies [ 11 ] : co=coL + ½ J ( 3 C o s Z O - - I - - ~ l s i n 2 O c o s 2 ~ )
,
(1)
coL is the Larmor frequency, J describes the strength of the anisotropic coupling, and r/is the asymmetry parameter describing the deviation of the anisotropic coupling from axial symmetry. The angles 0 and q~are the polar angles of the external magnetic field in the principal axis system of the coupling tensor. For the linear S13CN ion the chemical shift tensor is axially symmetric (~/= 0 ) around its long axis. In powder samples the spectra for all orientations are added to yield the powder lineshape. In the presence of rapid motions with correlation times below 1
ms the N M R lineshape will change [ 12 ]. Slower motions with correlation times re> 1 ms can be studied by 2D exchange N M R [ 13,14 ]. The intensity in a two-dimensional spectrum is the joint probability density S(Coe, cod; tm) of finding a molecular unit with a frequency coe before the mixing t i m e tm and with a frequency cod afterwards. For the S~3CN ion motions which change the orientation of the long axis of the ion are probed. The case of no reorientation manifests itself in a diagonal spectrum. Off-diagonal intensity (coe¢ cod) indicates reorientational processes during tm. A sequence of 2D spectra at a given temperature with mixing times in the range from 1 ms to several seconds is essential to obtain information about the dynamic evolution [ 15,16 ]. Estimates of correlationtime scales are possible without the assumption of a model just by measuring the ratio of off-diagonal intensity to diagonal intensity. A detailed analysis including a distribution of correlation times is based on the assumption of a motional model. For example, amorphous materials often show broad reorientational-angle distributions which have been described successfully with the isotropic rotational diffusion model [ 15-17 ]. This model involves small angular steps and yields a reorientation-angle distribution which depends only on the ratio of mixing time to correlation time tm/Zc. Often, the spectra cannot be described by a single correlation time zc, but with a distribution of correlation times. The log-Gaussian distribution with z0=exp(ln zc) as its center is applied here to the amorphous system I-10-Me-S~aCN: G(ln z) = (27c0"2 ) -X/2exp[ - (ln r - I n ~'0)2/20 "2 ]
(2) with LJo= log [exp (2a) ] as the total width in decades and ZJl/2 = 1.774.A~ as the full width at half height in decades.
4. Dielectric properties Like all aliphatic ionenes, the ionene I - 10-Me-SCN displays two major effects [ 6 ]: firstly, a conductivity contribution called 13-relaxation, and secondly a relaxation process called y-relaxation (Fig. 1 ). The latter process can be observed at lower temperatures. It exhibits a maximum in ~2 that shifts to higher fre-
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
z,oNq2x~ B = 6------~- '
-7-8-9-10.
ogs _
5 4
_~ -11-12. -13 4
5
~ 6 7 IO00/T [K-1]
0_1 8
Fig. 1. Arrhenius plot of the real part of the complexconductivity of I-10-Me-SCN with frequency as parameter. The "/-relaxation shifts to higher temperatures with increasingfrequency.The critical frequencyof 0.1 Hz is at 225 K. quencies with increasing temperature. The two processes can be differentiated by the following equations [ 9 ]:
1
t2
_
~o
p
exp(-Adc/kT) .
153
(8) (9)
The temperature dependence of the dc conductivity, and the critical frequency are described by Eqs. ( 7 ) ( 9 ) . N ~ V is the density of the mobile ions, q is the charge, Xo is the hopping distance, k is the Boltzmann constant, and Vo is an oscillatory frequency of the anion. Ad~ is the value for the activation energy of the dc conductivity. The dc activation energy of I - 10-MeSCN is around 106 kJ/mol, and the preexponential factor of the critical frequency is 6 × 1013 Hz, indicating a cooperative process. The critical frequency at Tg is 59 kHz, and the critical temperature for a hopping rate of 1 kHz is 267 K. For a detailed discussion of the anion conductivity see eslewhere [9,18].
~"(o9) = e"(o)) + G'el.x(o)) ,
(3)
N M R results
a(0) ( o)P-- 1~ " - o9-1+ e~= ~o o)f ,1'
(4)
~;;lax=Im 1 + (--:l~Z) ci "
(5)
Fig. 2 shows the static 13C N M R spectra of I 10-Me-S13CN (Tg=292 K) for several temperatures. The aliphatic chain segments have a stronger dipole-dipole coupling with the protons than the L3Cnuclei in 513CN - . Therefore, before detection, their signal can be suppressed with a waiting time during which their intensity disappears (gated decoupling). At 205 K the spectrum appears to be a rigid Pake pattern. A change of the lineshape indicating the onset of motion is observed at 225 K. At 260 K/275 K there is already reorientation with isotropic parts on the time scale of the 1D N M R experiment. However, the glass transition of 1-10-Me-SCN is 292 K, a temperature where the motional rate of the counterions is in the range of 0.1 MHz. In the N M R experiment rotational motion is observed. Hence, it is necessary to extract the activation energy or the correlation times, respectively, to compare the reorientational motion observed by N M R with the conductivity data obtained by dielectric spectroscopy. According to the dielectric investigations the correlation time at 250 K should be in the range of 10 ms. Therefore, static L3C 2D exchange experiments are performed between 215 K and 260 K with various mixing times (Figs. 3 and 4). In Fig. 3, 2D spectra with a mixing time of 50 ms
The dc conductivity is characterized with a ( 0 ) ; Co is the vacuum permittivity. At the critical frequency o)s, the dispersion of the conductivity begins. The parameter p describes the slope of that dispersion in the log frequency-log conductivity-plot. Eq. (5) is the well-known Cole-Cole function. The parameter determines the width of the symmetric distribution of the mean relaxation time r, and Ae is the relaxation strength. With o-*(to)=ioJ%e*(o)) Eq. (4) can be written as
a( oJ ) = a ( O) +a(O).o~p/o~f.
(4a)
The 7-relaxation of all ionenes exhibits an Arrheniuslike behavior (Eq. ( 6 ) ) . Especially, the activation energy of 1-10-Me-SCN is 38 k J / m o l with a preexponential factor of 3 × 10- ~5 s. z = zoexp ( E a / k T ) , B a' (0, T) = ~ e x p ( - A d ¢ / k T
(6) ) ,
(7)
154
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
Fig. 2. Static ~3C-NMR spectra of I - 10-Me-S ~3CN ( Tg = 292 K ). The spectral range shown for each individual plot is 400 ppm.
and corresponding simulations with the isotropic rotational diffusion model for several temperatures are shown. The off-diagonal intensity rises with increasing temperature and decreasing correlation time. Signals are found in the whole frequency plane and exhibit no relevant structure. Hence, reorientations about all angles are allowed. At 250 K, the dynamics are already spatially isotropic. The extracted activation energy is 107 kJ/mol+_ 6 kJ/mol and the preexponential factor is 2 × 1024 Hz ( + 1 decade), which is in remarkable agreement with the dielectric resuits. It should be noted that the NMR deals with a tensor of the second rank in contrast to the dielectric spectroscopy, which probes the dynamical processes with the reorientation of the dipole moment (which is a tensor of the first rank), thus for small step diffusion 3 (Zdielecnc) = (ZNMR) [ 19 ]. The diffusive character of the dynamics of the counterions and their unusually high activation energy imply distinct cooperativity of the anion mo-
tion. It is comparable with a glass transition process. Correspondingly, there must be a transition temperature which is 205 K according to the NMR experiment. At this temperature almost a rigid limit Puke spectrum is observed. The simulated spectra, however, show some deviations from the experimental spectra. The reason is an axial reorientation of the rhodanide anion in the domain of microseconds which affects the diagonal spectrum. We tried to simulate such a behavior by superimposing powder patterns with various asymmetry parameters ~/. Because there is no off-diagonal intensity at tm= 200 ms at low temperatures, 13C spin diffusion can be excluded as a relevant exchange mechanism in our spectra. As mentioned above the spectrum at 215 K is not a pure Puke spectrum. Its intensity is increased as compared to a completely rigid pattern and its width increases with mixing time (Fig. 5). Small angle librational motions could explain this observation. For an evaluation of their angular amplitudes some spectra are simulated under the assumption of slow smallangle librational motions. The spectrum with a mixing time of 1 ms is the starting point for the spectrum with a mixing time of 20 ms. Longer mixing times do not lead to further widening. These small-angle librational motions may be coupled to the polymer chain motions in the glassy state, which have been described as trans-gauche isomerizations, and which were assigned as y-relaxation on the basis of dielectric experiments [4 ]. Similar reorientations are observed in other polymer systems as well (e.g. polyethylene) [ 20 ]. In the same manner as for the simulation of the diffusive motion a superposition of powder patterns with different ~/values was necessary also in this case, because the librations have correlation times in the range of milli- and microseconds, so that the diagonal spectrum is affected. Investigations at lower temperatures would be necessary to find a rigid-limit Puke pattern. The observed small-angle librational motion is slow on the time scale of the 1D NMR experiment. In summary, the axially symmetrical rhodanide anion performs small angle librational motions at 215 K with an angular amplitude of about 10 ° and an average correlation time of approximately 3 ms.
R.-R. Rietz et al. / Solid State Ionics 68 (I 994) 151-158
155
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156
R.-R. Rietz et al. / S o l i d State lonics 68 (1994) 151-158
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Fig. 4. Static ~aC-2D-NMR exchange spectra for the S13CN-counterion in I- 10-Me-SCN at 250 K for different mixing times. The spectral width of the plots is 400 ppm (frequency axes; vertical: 092, horizontal: ogt ). 6. Conclusions The dynamics o f S C N counterions of the ionically conducting amorphous polyelectrolyte I- 1 0 - M e - S C N have been investigated by applying one- and two-dimensional 13C-NMR techniques. About 40 K below Tg (292 K ) , the anion dynamics are found to be fast on the N M R timescale and spatially isotropic in nature. The activation energy for the anion m o t i o n has
been found to be about 107 k J / m o l and the preexponential factor is about 1024 Hz. These results are in g o o d agreement with those obtained by dielectric spectroscopy. The relatively high activation energy indicates a cooperative character of the anion motion. Future experiments are necessary to characterize the influence of anion geometry and polyelectrolyte chain rigidity on the anion transport.
157
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
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Fig. 5. Pake spectra of the S13CN counterions in I-10-Me-SL3CN demonstrating small angle librations.
158 7.
R.-R. Rietz et al. / Solid State lonics 68 (1994) 151-158
Acknowledgement This work has been financially supported by the
Deutsche Forschungsgemeinschaft (Sonderfors c h u n g s b e r e i c h 262, p r o j e c t s S- 10, D - 10).
References [ 1 ] A. Rembaum, J. Macromol. Sci. Chem. 3 (1969) 87. [2] F. Kremer, L. Dominquez, W.H. Meyer and G. Wegner, Polymer 30 (1989) 2023. [3] H.-U. Simmrock, A. Mathy, L. Dominquez, W.H. Meyer and G. Wegner, Adv. Mat. Angew. Chem. 101 (1989) 1148. [4] D. Schaefer, R.R. Rietz, W.H. Meyer and H.W. Spiess, Ber. Bunsenges. Physik. Chem. 95 ( 1991 ) 1071. [5] W.H. Meyer, J. Pecherz, A. Mathy and G. Wegner, Adv. Mater. 3 (1991) 153. [6] W.H. Meyer, R.R. Rietz, D. Schaefer and F. Kremer, Electrochim. Acta 37 (1992) 1491. [7]R.R. Rietz, D. Schaefer, W.H. Meyer and H.W. Spiess, Electrochim. Acta 37 (1992) 1657.
[8] K. Funke, Solid State Ionics 18/19 (1986) 183; Mat. Res. Soc. Symp. Proc. 125 (1989)43. [ 9 ] R.-R. Rietz and W.H. Meyer, Polymers Adv. Tech. 4 ( 1993 ) 164. [ 10] L. Dominiquez, W.H. Meyer and G. Wegner, Makromol. Chem. Rapid Commun. 8 (1987) 151. [ 11 ] M. Mehring, Principles of High Resolution NMR in Solids (Springer, Berlin, 1983). [ 12] H.W. Spiess, in: NMR-Basic Principles and Progress, Vol. 15 (Springer, Berlin, 1978 ). [ 13 ] J. Jeener, B.H. Meier, P. Bachmann and R.R. Ernst, J. Chem. Phys. 71 (1979) 4546. [ 14] A. Hagemeyer, K. Schmidt-Rohr and H.W. Spiess, Adv. Magn. Reson. 13 (1989) 85. [ 15 ] S. Wefing and H.W. Spiess, J. Chem. Phys. 89 ( 1988 ) 1219, 1234. [16] S. Kaufmann, S. Wefing, D. Schaefer and H.W. Spiess, J. Chem. Phys. 93 (1990) 197. [ 17 ] D. Schaefer, H.W. Spiess, U.W. Suter and W.W. Fleming, Macromol. 23 (1990) 3431. [ 18] R.-R. Rietz, W.H. Meyer, F. Kremer and G. Wegner, to be published. [19] H. Sillescu, J. Chem. Phys. 54 (1971) 2110. [20] D. Hentschel, H. Sillescu and H.W. Spiess, Polymer 28 (1984) 1078.