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Investigation of dielectric relaxation processes in polar molecules introduced into a polymer matrix
Dielectric
relaxation
processes
in polar
587
molecules
REFERENCES 1. M. ‘M. KOTON, SMIRNOVA,
V. V. KUDRYAVTSEV,
B. G. BELEN’KII
2. 0. V. KALLISTOV, 3. H. VINK Solutions).
Rasseyaniye
“Nauka”,
5. V. Ye. ESKIN
V. B. MELAR,
khimii
49:
V. Ye.
387,
1976
Chem.
109: 249, 1967
polimerov
(Scattering
of Light
by Polymer
Vysokomol.
soyed.
A19:
533,
1977
(Trams-
19: 3, 612, 1!)77)
M. A. LAZAREVA,
19: 4, 1052,
V. I. KOLEGOV,
Vyaokomol.
B. G. BELEN’KII
and M. M. KOTON,
Dokl.
A11N
soycd.
P. I’. NEFEDOV,
M. A. ALEKSANDROVA and Sci. U.S.S.R.
A19:
lS57 (‘Tr;tnslated in Polymer
907,
197i)
8. M. L. WALLACH,
J. Polymer
ESKIN,
Sci. 5, 4-3:
653, l%ii
I. A. BARANOVSKAYA,
V. P. SKLIZKOVA, u.s.s.1t.
prikl.
389, 1975
7. B. G. BELEN’KII,
9. V. Ye.
M. I. BESSONOV,
Zh.
1973
Fci. U.S.S.R.
G. P. P. NEFEDOV, 220:
Mnkromol.
ST-eta rastvorami
aud I. A. BARANOVSKAYA,
in Polymer
SSSR
V. P. SKLIZKOVA, V. I. KOLEGOV,
lab. 38: 711, 1972
and G. DAHLSTROM,
4. V. Ye. ESKIN,
latrd
Zavodsk.
and
Vysokomol.
98: 10, %!)I),
soyetl.
AlS:
2362,
1976
V. V. KUDRYAVTSEV
ant1
(Translated
Sci,
in Polymer
1976)
10. W. H. STOCKMAYER 11. T. M. BIRSHTEIN,
M. M. BOTON,
,J. Polynxr
and M. FIXMAN,
Vysokomol
%<
. saved. Al!?: 54, 197i (Translated
in Polymer
Sci. U.S.S.R.
19: 1, 63, 1977)
Sciencel1,S.S.R.7‘01.21, ~0. 587-592. PergamonPressLtd. l!:;D. Priutcdin Poland
0032%3950/79/0301-05W$O7.5OjQ
Polymer @
INVESTIGATION OF DIELECTRIC RELAXATION PROCESSES IN POLAR MOLECULES INTRODUCED INTO A POLYMER MATRIX” A.
P.
STETSOVSKII, L. A.
ZHURAVLEVA
and RI. I. KHAZANOV
Central Scientific Rcsearcll Insti t&c fcr Scientific ant1 Technical Information and Trchnico-Eeoncmic Research (Rereivecl 14 The dielectric
propcrties
nitrile
with
transformer
masses
of 8000 and 40,000
the temperature tion
processes
similar
esses in polymers in the mixtures
* Vysokomol.
have 180-+
100°C.
dependence
A21:
Ko.
chloroform
stereolcgular
rubbers
in the frcqllency
range
lt has bee11 est,ablished
group
and
co< pprativo
the c yuat ic.n
3, 536-541,
1979.
lime
with
and
aceto-
molecular
l-1010 Hz and in
that dielectric
relaxa-
(dipole-segment,al)
in t’lrrl rnixturcxs investipated.
of the relaxation
obeys
1978)
of chlorohcnzene,
dirinyl
been F:ndicd
be observed
investigated
soyed.
two
to the dipole
may
that the temperature
of mixtures
oil and -
range
Marc!:
proc-
It has been
for t,lle cooperative
shown
processes
A.
-588
P.
where
r0 is a pm-exponential
energy
for cooperative
values
of U and r0 do not depend
polymeric
matrix
factor,
processes
STETSOVSXII
et al.
TB is the glass temperature
of dipole
relaxation.
on the concentration
but are determined
and U is the activation
It has been established
by their physical
that the
of the polar molecules and chemical
in the
nature and struc-
ture.
concept
THE
exists that dielectrically
currently
be observed
in polymers
active relaxation
which are caused by the presence
processes
can
of polar molecules
of low molecular substances and which are similar in their behaviour to processes of dipole-group relaxation [l, 21. Since only a limited number of papers have been devoted TABLE
to investigations
1. PHYSICO-CHEMICAL
of this type and also considering
PROPERTIES OF THE COMPONENTS OF THE MIXTURES STUDIED I
M
Substance Transformer
oil
q at 5O”C, poise
(7-10) x 103
SKD-2
40 x 103 41
P? g/cm3
Tg from DTA data, “K
0.86
182
0.92
173
8 x 1O-3
0.92
3.4 x 10-a*
0.78
173 -
8.3x 10-e
.SKD-1 Aoetonitrile
that investiga-
’
2.5 x lo*
Chlorobenzene
112
8.0 x 1O-s*
1.10
-
Chloroform
119
5.6 x 10-3*
1.49
-
*
Viscosity
at 20°C.
tions of these processes can provide a valuable contribution to the understanding ‘of the mechanisms of relaxation phenomena in polymers, we thought it desirable to attempt to throw light on the characteristics of certain features of the relaxation behaviour of such systems and to assess how the parameters of the relaxation processes depend on the chemical nature and structure both of the molecules TABLE
2. COMPOSITION AND PARAMETERS OF THE RELAXATION
PROCESSES IN THE MIXTURES
INVESTIGATED Solvent Matrix
Solvent
-
conlog reo
/mole
16 17
5.5 5.3
15
168
10.9
157
5.0
15 15
10
11.4
156 156
8.2 8.5
18 18
30 3
11.0
160
4.8
Chlorobenzene Chloroform
40 10 3
11.6 10.3 11.1
,,
Ditto
10
10-5
9,
Cl~oroform
30
159 147 138 172 169
,, “SK;;-2
Acetonitrile Chlorobenzene
-
6.5 6.8
11.7 11.6
I, ..&.D_l
u, l-1, I 16 16
10 20
oil
OK
5.2 5.6
Chlorobenzene Ditto
‘Transformer Ditto
Tg,
-
15
Dielectric relaxation processes in polar molecules
589
o f the polymeric m a t r i x a n d also o f t h e polar molecules of the simple s u b s t a n c e s i n t r o d u c e d into the polymeric m a t r i x . F o r this p u r p o s e we i n v e s t i g a t e d t h e dielectric properties of m i x t u r e s of chlorobenzene, chloroform a n d acetonitrile w i t h t r a n s f o r m e r oil a n d with t w o specimens of a divinyl stereoregular r u b b e r {SKD) w i t h molecular m~sses of 8 × 103 (SKD-1) a n d 40 × l03 (SKD-2). Some properties o f the substances studied are shown in Table 1 a n d ~he compositions of the mixt u r e s are given in Table 2. The investigations were made with the following Soviet equipment: "Yantar", "Tangens" and "Rezonans". The mixtures studied were poured into the cells of the equipment and rapidly cooled to a temperature of --180°C, after which the values of Ez and ~2 were measured at the following frequencies as the temperature was raised at the rate of 0.2-0.4°C/ /rain: l; 10; 102; 5× 104 and l0 s I-Iz. Some of the relationships obtained are shown graphically in Fig. 1. I t m a y be seen f r o m the curves in Fig. la, t h a t t w o regions of dielectric r e l a x a t i o n are f o u n d in m i x t u r e s o f t r a n s f o r m e r oil with chlorobenzene b u t in all the r e m a i n i n g cases there is only one such region. I n order to use the t e m p e r a t u r e d e p e n d e n c e of the dielectric loss coefficient to clarify t h e n a t u r e of t h e relaxation processes, Tmax corresponding to the m a x i m u m ~ at t h e various frequencies was d e t e r m i n e d a n d the d a t a o b t a i n e d were used to plot t h e relationships log T = ~(1/Tmax) some of w h i c h are s h o w n on t h e glass in Fig. 2 ( r = 1/2uf). ~z
E~
c2
1.5b
0.3F
l'g
g'l
-200
-150
-100
T, °C
- 150
- z7o
T, %
FIG. I. Temperature dependence of the dielectric loss coefficient at a frequency of I0 Hz for: a--mixtures of transformer oil with the following percontages of chlorobcnzene: 1-- 10; 2--20 and 3--40%; and b--for mixtures of SKD-1 with 1--10% chloroform; 2--10% chlorobenzene and 3-- 3 % aceton~ ~rile.
1i90
A . P . STETSOVSKIIet al. /
It was established that, in all cases except low temperature relaxation processes in mixture of transformer oil with chlorobenzene, log ~ depends on 1/Tmax in a non-linear manner and the relationship may be described by the equation
[3] U *=Zo exp ( 2 - ~ g In T-C-Tg~ .
T--TJ
(1)
where ~0 is a pre-exponential factor, U is the activation energy and Tg the glass temperature. The values of these quantities, which characterize the relaxation processes in the mixture studied and which were calculated from the experimental data, are shown in Table 2; the logarithm of the relaxation times at 20°C (~20), calculated from equation (1), are also presented. The dependence of log ~ oll 1/Tmax for low temperature processes in mixtures of chlorobenzene with transformer oil m a y be satisfactorily described b y straight lines (Fig. 2b). Since no relaxation processes were found in pure transformer oil or in th~ rubbers, within the limits of sensitivity of the apparatus used, the relaxation processes found in the mixtures are caused b y the pre~ence in them of polar molecules of chlorobenzene, chloroform and acetoni~rile. This is confirmed b y the fact that the increase in these maxima is approximately proportional to the. increase in the concentration of the polar component in the mixtures. The form of the relationship log r=- ~(]/Tmax) that has been found (Fig. 2) is evidence of the cooperative nature of the observed relaxation processes, which are similar to dipole-segmental relaxation processes in polymers, since they appear at T > T g and are accompanied b y a strong degree of dispersion in the dielectric permeability. The low temperature relaxation process in mixtures of transformer oil with chlorobenzene is, in its turn, similar to dipole-group relaxation processes in polymers in its activation energy (5.,t-6 keal/mole), in the fact that it appears at temperatures below Tg and also in the ratio of the width and amplitude of the c2 maxima as compared with the maxima corresponding to cooperative processes
[]]. The ,existence of two types of relaxation processes in mixtures of transformer oil with chlorobenzene, whose molecule does not have the possibility of internal rotation, m a y be explained only b y the existence of two types diblectrically active transitions as a result of which a change in the direction of the dipole moment of the chlorobenzene molecule can occur: namely, a non-cooperative transition when the change in the direction of the dipole moment is not accompanied b y changes in the positioning of nearest neighbours; and a cooperative transition when a change in the direction of the dipole moment is connected with a corresponding regrouping in the positioning of nearest neighbours. The fact ~Jlat two types of relaxation process are found only in mixtures o f chlorobenzcne with transformer oil and are not found in mixtures of ehlorobenz-
Dielectric relaxation processes in polar molecules
591"
ene with SKD, chloroform with transformer oil and in the other mixtures is evidence that, in order for non-cooperative types of transition to exist, certain conditions must be fulfilled (the,existence of "voids", "holes" etc.), which are determined b y the physico-ehemical structure not only of the polar molecules,
l~gv
-1E~
a
I
I log"z"
234
I 4
~
[_
8
/2
i I .....
I
I
E
2
4
b"
]giG. 2. ' F e m p e r a t q r e d e p e n d e n c e ~,f f o r m e r oil w i t h 1 - - 1 0 % eh!oroft)rm 2 a n d 2 ' - - 1 0 ; 3 a n d 3 " - - 2 0 a n d -I a n d benzene
oK
Islle dip,~!e rebT,x~¢,io]a t i m e "\;r a - - m i x t u i - e s o f t r a n s 'rod ~ i t h tI~e follov, in[~ t),~'reentages of" e h l o r o b e n z e n e : 4 ' - - 4 0 % ; b - - m i x t u r e s (,t S K D - ] wit, h 1 - - 1 0 % ehloroa n d 2 - 10%,, c h l o r o f o r m .
A. P. STETSOVSEII et al.
692
but also of the matrix itself as well as by the character of intra- and intermolecular interactions in the system. It may be seen from the data in Table 2 that, within the concentration range of the low molecular
component
investigated,
the glass temperature
of the mix-
tures uniformly decreases as the concentration of the low molecular component is increased, the values of z0 and U remaining unchanged. On the other hand, by comparing
the values of z0 and U calculated
benzene-transformer with chlorobenzene,
for the following
mixtures:
chloro-
oil (zO= lo-16) chlorobenzene-SKD (z,= lo-15) and SKD chloroform and acetonitrile; it may be seen that these quan-
tities depend on the chemical nature and structure of the polar molecule and the polymeric matrix. Attention should also be given to the fact that the molecular weight dimensions of the polar molecule and the viscosity of the system, on the one hand, are not connected with, on the other hand, values of the relaxation times at sufficiently high temperatures (in the limit as T + co); such a connection is predicted by the well known Debye equation z=4xqa3/3kT. For example, in mixtures of chlorobenzene with SKD, despite a change in viscosity by a factor of more than 40, the relaxation times z2,, and z0 remain unchanged whereas, for mixtures of chloroform and acetonitrile with SKD, z0 and zZOare found to be the same although the molecular weight of the chloroform molecule is double that of the acetonitrile molecule and, in mixtures with chloroform and chlorobenzene, which have almost identical molecular masses, the values of zgOdiffer by a factor of 10 and those of z0 differ by a factor of 1000. Translated by G. F. MODLEN
REFERENCES 1. Elektricheskiye ed., “Khimiya”,
svoistva
polimerov
(Electrical
Properties
of Polymers),
B. I. Sazhin,
1977
2. G. A. LUSHCHEIKIN, L. I. YEMEL’YANOVA
V. V. SUBOVA,
V. D. VOROB’YEV,
and Ye. G. SJZKUBOVA,
M. L. DOBROKHOTOVA,
Vysokomol.
soyed.
B17:
159,
1975
(Not translated in Polymer Sci. U.S.S.R.) 3. A. P. STETSOVSKII, U.S.S.R.
Vysokomol.
17: 9, 2192, 1975)
soyed. A17:
1903,
1975 (Translated
in Polymer
Sci.
relaxation
processes
in polar
587
molecules
REFERENCES 1. M. ‘M. KOTON, SMIRNOVA,
V. V. KUDRYAVTSEV,
B. G. BELEN’KII
2. 0. V. KALLISTOV, 3. H. VINK Solutions).
Rasseyaniye
“Nauka”,
5. V. Ye. ESKIN
V. B. MELAR,
khimii
49:
V. Ye.
387,
1976
Chem.
109: 249, 1967
polimerov
(Scattering
of Light
by Polymer
Vysokomol.
soyed.
A19:
533,
1977
(Trams-
19: 3, 612, 1!)77)
M. A. LAZAREVA,
19: 4, 1052,
V. I. KOLEGOV,
Vyaokomol.
B. G. BELEN’KII
and M. M. KOTON,
Dokl.
A11N
soycd.
P. I’. NEFEDOV,
M. A. ALEKSANDROVA and Sci. U.S.S.R.
A19:
lS57 (‘Tr;tnslated in Polymer
907,
197i)
8. M. L. WALLACH,
J. Polymer
ESKIN,
Sci. 5, 4-3:
653, l%ii
I. A. BARANOVSKAYA,
V. P. SKLIZKOVA, u.s.s.1t.
prikl.
389, 1975
7. B. G. BELEN’KII,
9. V. Ye.
M. I. BESSONOV,
Zh.
1973
Fci. U.S.S.R.
G. P. P. NEFEDOV, 220:
Mnkromol.
ST-eta rastvorami
aud I. A. BARANOVSKAYA,
in Polymer
SSSR
V. P. SKLIZKOVA, V. I. KOLEGOV,
lab. 38: 711, 1972
and G. DAHLSTROM,
4. V. Ye. ESKIN,
latrd
Zavodsk.
and
Vysokomol.
98: 10, %!)I),
soyetl.
AlS:
2362,
1976
V. V. KUDRYAVTSEV
ant1
(Translated
Sci,
in Polymer
1976)
10. W. H. STOCKMAYER 11. T. M. BIRSHTEIN,
M. M. BOTON,
,J. Polynxr
and M. FIXMAN,
Vysokomol
%<
. saved. Al!?: 54, 197i (Translated
in Polymer
Sci. U.S.S.R.
19: 1, 63, 1977)
Sciencel1,S.S.R.7‘01.21, ~0. 587-592. PergamonPressLtd. l!:;D. Priutcdin Poland
0032%3950/79/0301-05W$O7.5OjQ
Polymer @
INVESTIGATION OF DIELECTRIC RELAXATION PROCESSES IN POLAR MOLECULES INTRODUCED INTO A POLYMER MATRIX” A.
P.
STETSOVSKII, L. A.
ZHURAVLEVA
and RI. I. KHAZANOV
Central Scientific Rcsearcll Insti t&c fcr Scientific ant1 Technical Information and Trchnico-Eeoncmic Research (Rereivecl 14 The dielectric
propcrties
nitrile
with
transformer
masses
of 8000 and 40,000
the temperature tion
processes
similar
esses in polymers in the mixtures
* Vysokomol.
have 180-+
100°C.
dependence
A21:
Ko.
chloroform
stereolcgular
rubbers
in the frcqllency
range
lt has bee11 est,ablished
group
and
co< pprativo
the c yuat ic.n
3, 536-541,
1979.
lime
with
and
aceto-
molecular
l-1010 Hz and in
that dielectric
relaxa-
(dipole-segment,al)
in t’lrrl rnixturcxs investipated.
of the relaxation
obeys
1978)
of chlorohcnzene,
dirinyl
been F:ndicd
be observed
investigated
soyed.
two
to the dipole
may
that the temperature
of mixtures
oil and -
range
Marc!:
proc-
It has been
for t,lle cooperative
shown
processes
A.
-588
P.
where
r0 is a pm-exponential
energy
for cooperative
values
of U and r0 do not depend
polymeric
matrix
factor,
processes
STETSOVSXII
et al.
TB is the glass temperature
of dipole
relaxation.
on the concentration
but are determined
and U is the activation
It has been established
by their physical
that the
of the polar molecules and chemical
in the
nature and struc-
ture.
concept
THE
exists that dielectrically
currently
be observed
in polymers
active relaxation
which are caused by the presence
processes
can
of polar molecules
of low molecular substances and which are similar in their behaviour to processes of dipole-group relaxation [l, 21. Since only a limited number of papers have been devoted TABLE
to investigations
1. PHYSICO-CHEMICAL
of this type and also considering
PROPERTIES OF THE COMPONENTS OF THE MIXTURES STUDIED I
M
Substance Transformer
oil
q at 5O”C, poise
(7-10) x 103
SKD-2
40 x 103 41
P? g/cm3
Tg from DTA data, “K
0.86
182
0.92
173
8 x 1O-3
0.92
3.4 x 10-a*
0.78
173 -
8.3x 10-e
.SKD-1 Aoetonitrile
that investiga-
’
2.5 x lo*
Chlorobenzene
112
8.0 x 1O-s*
1.10
-
Chloroform
119
5.6 x 10-3*
1.49
-
*
Viscosity
at 20°C.
tions of these processes can provide a valuable contribution to the understanding ‘of the mechanisms of relaxation phenomena in polymers, we thought it desirable to attempt to throw light on the characteristics of certain features of the relaxation behaviour of such systems and to assess how the parameters of the relaxation processes depend on the chemical nature and structure both of the molecules TABLE
2. COMPOSITION AND PARAMETERS OF THE RELAXATION
PROCESSES IN THE MIXTURES
INVESTIGATED Solvent Matrix
Solvent
-
conlog reo
/mole
16 17
5.5 5.3
15
168
10.9
157
5.0
15 15
10
11.4
156 156
8.2 8.5
18 18
30 3
11.0
160
4.8
Chlorobenzene Chloroform
40 10 3
11.6 10.3 11.1
,,
Ditto
10
10-5
9,
Cl~oroform
30
159 147 138 172 169
,, “SK;;-2
Acetonitrile Chlorobenzene
-
6.5 6.8
11.7 11.6
I, ..&.D_l
u, l-1, I 16 16
10 20
oil
OK
5.2 5.6
Chlorobenzene Ditto
‘Transformer Ditto
Tg,
-
15
Dielectric relaxation processes in polar molecules
589
o f the polymeric m a t r i x a n d also o f t h e polar molecules of the simple s u b s t a n c e s i n t r o d u c e d into the polymeric m a t r i x . F o r this p u r p o s e we i n v e s t i g a t e d t h e dielectric properties of m i x t u r e s of chlorobenzene, chloroform a n d acetonitrile w i t h t r a n s f o r m e r oil a n d with t w o specimens of a divinyl stereoregular r u b b e r {SKD) w i t h molecular m~sses of 8 × 103 (SKD-1) a n d 40 × l03 (SKD-2). Some properties o f the substances studied are shown in Table 1 a n d ~he compositions of the mixt u r e s are given in Table 2. The investigations were made with the following Soviet equipment: "Yantar", "Tangens" and "Rezonans". The mixtures studied were poured into the cells of the equipment and rapidly cooled to a temperature of --180°C, after which the values of Ez and ~2 were measured at the following frequencies as the temperature was raised at the rate of 0.2-0.4°C/ /rain: l; 10; 102; 5× 104 and l0 s I-Iz. Some of the relationships obtained are shown graphically in Fig. 1. I t m a y be seen f r o m the curves in Fig. la, t h a t t w o regions of dielectric r e l a x a t i o n are f o u n d in m i x t u r e s o f t r a n s f o r m e r oil with chlorobenzene b u t in all the r e m a i n i n g cases there is only one such region. I n order to use the t e m p e r a t u r e d e p e n d e n c e of the dielectric loss coefficient to clarify t h e n a t u r e of t h e relaxation processes, Tmax corresponding to the m a x i m u m ~ at t h e various frequencies was d e t e r m i n e d a n d the d a t a o b t a i n e d were used to plot t h e relationships log T = ~(1/Tmax) some of w h i c h are s h o w n on t h e glass in Fig. 2 ( r = 1/2uf). ~z
E~
c2
1.5b
0.3F
l'g
g'l
-200
-150
-100
T, °C
- 150
- z7o
T, %
FIG. I. Temperature dependence of the dielectric loss coefficient at a frequency of I0 Hz for: a--mixtures of transformer oil with the following percontages of chlorobcnzene: 1-- 10; 2--20 and 3--40%; and b--for mixtures of SKD-1 with 1--10% chloroform; 2--10% chlorobenzene and 3-- 3 % aceton~ ~rile.
1i90
A . P . STETSOVSKIIet al. /
It was established that, in all cases except low temperature relaxation processes in mixture of transformer oil with chlorobenzene, log ~ depends on 1/Tmax in a non-linear manner and the relationship may be described by the equation
[3] U *=Zo exp ( 2 - ~ g In T-C-Tg~ .
T--TJ
(1)
where ~0 is a pre-exponential factor, U is the activation energy and Tg the glass temperature. The values of these quantities, which characterize the relaxation processes in the mixture studied and which were calculated from the experimental data, are shown in Table 2; the logarithm of the relaxation times at 20°C (~20), calculated from equation (1), are also presented. The dependence of log ~ oll 1/Tmax for low temperature processes in mixtures of chlorobenzene with transformer oil m a y be satisfactorily described b y straight lines (Fig. 2b). Since no relaxation processes were found in pure transformer oil or in th~ rubbers, within the limits of sensitivity of the apparatus used, the relaxation processes found in the mixtures are caused b y the pre~ence in them of polar molecules of chlorobenzene, chloroform and acetoni~rile. This is confirmed b y the fact that the increase in these maxima is approximately proportional to the. increase in the concentration of the polar component in the mixtures. The form of the relationship log r=- ~(]/Tmax) that has been found (Fig. 2) is evidence of the cooperative nature of the observed relaxation processes, which are similar to dipole-segmental relaxation processes in polymers, since they appear at T > T g and are accompanied b y a strong degree of dispersion in the dielectric permeability. The low temperature relaxation process in mixtures of transformer oil with chlorobenzene is, in its turn, similar to dipole-group relaxation processes in polymers in its activation energy (5.,t-6 keal/mole), in the fact that it appears at temperatures below Tg and also in the ratio of the width and amplitude of the c2 maxima as compared with the maxima corresponding to cooperative processes
[]]. The ,existence of two types of relaxation processes in mixtures of transformer oil with chlorobenzene, whose molecule does not have the possibility of internal rotation, m a y be explained only b y the existence of two types diblectrically active transitions as a result of which a change in the direction of the dipole moment of the chlorobenzene molecule can occur: namely, a non-cooperative transition when the change in the direction of the dipole moment is not accompanied b y changes in the positioning of nearest neighbours; and a cooperative transition when a change in the direction of the dipole moment is connected with a corresponding regrouping in the positioning of nearest neighbours. The fact ~Jlat two types of relaxation process are found only in mixtures o f chlorobenzcne with transformer oil and are not found in mixtures of ehlorobenz-
Dielectric relaxation processes in polar molecules
591"
ene with SKD, chloroform with transformer oil and in the other mixtures is evidence that, in order for non-cooperative types of transition to exist, certain conditions must be fulfilled (the,existence of "voids", "holes" etc.), which are determined b y the physico-ehemical structure not only of the polar molecules,
l~gv
-1E~
a
I
I log"z"
234
I 4
~
[_
8
/2
i I .....
I
I
E
2
4
b"
]giG. 2. ' F e m p e r a t q r e d e p e n d e n c e ~,f f o r m e r oil w i t h 1 - - 1 0 % eh!oroft)rm 2 a n d 2 ' - - 1 0 ; 3 a n d 3 " - - 2 0 a n d -I a n d benzene
oK
Islle dip,~!e rebT,x~¢,io]a t i m e "\;r a - - m i x t u i - e s o f t r a n s 'rod ~ i t h tI~e follov, in[~ t),~'reentages of" e h l o r o b e n z e n e : 4 ' - - 4 0 % ; b - - m i x t u r e s (,t S K D - ] wit, h 1 - - 1 0 % ehloroa n d 2 - 10%,, c h l o r o f o r m .
A. P. STETSOVSEII et al.
692
but also of the matrix itself as well as by the character of intra- and intermolecular interactions in the system. It may be seen from the data in Table 2 that, within the concentration range of the low molecular
component
investigated,
the glass temperature
of the mix-
tures uniformly decreases as the concentration of the low molecular component is increased, the values of z0 and U remaining unchanged. On the other hand, by comparing
the values of z0 and U calculated
benzene-transformer with chlorobenzene,
for the following
mixtures:
chloro-
oil (zO= lo-16) chlorobenzene-SKD (z,= lo-15) and SKD chloroform and acetonitrile; it may be seen that these quan-
tities depend on the chemical nature and structure of the polar molecule and the polymeric matrix. Attention should also be given to the fact that the molecular weight dimensions of the polar molecule and the viscosity of the system, on the one hand, are not connected with, on the other hand, values of the relaxation times at sufficiently high temperatures (in the limit as T + co); such a connection is predicted by the well known Debye equation z=4xqa3/3kT. For example, in mixtures of chlorobenzene with SKD, despite a change in viscosity by a factor of more than 40, the relaxation times z2,, and z0 remain unchanged whereas, for mixtures of chloroform and acetonitrile with SKD, z0 and zZOare found to be the same although the molecular weight of the chloroform molecule is double that of the acetonitrile molecule and, in mixtures with chloroform and chlorobenzene, which have almost identical molecular masses, the values of zgOdiffer by a factor of 10 and those of z0 differ by a factor of 1000. Translated by G. F. MODLEN
REFERENCES 1. Elektricheskiye ed., “Khimiya”,
svoistva
polimerov
(Electrical
Properties
of Polymers),
B. I. Sazhin,
1977
2. G. A. LUSHCHEIKIN, L. I. YEMEL’YANOVA
V. V. SUBOVA,
V. D. VOROB’YEV,
and Ye. G. SJZKUBOVA,
M. L. DOBROKHOTOVA,
Vysokomol.
soyed.
B17:
159,
1975
(Not translated in Polymer Sci. U.S.S.R.) 3. A. P. STETSOVSKII, U.S.S.R.
Vysokomol.
17: 9, 2192, 1975)
soyed. A17:
1903,
1975 (Translated
in Polymer
Sci.