- Email: [email protected]
Conductivity of polymer films at high frequencies
1996
L . I . BOGUSLAVSKIIand L. S. STILBANS
CONCLUSIONS (1) V i n y l h y d r o q n i n o n e d i b e n z o a t e h a s b e e n c o p o l y m e r i z e d w i t h a c r y l i c a n d m e t h a c r y l i c a c i d i n t h e p r e s e n c e o f a z o b i s i s o b u t y r o r t i t r i l e a t 60 °, a n d t h e r e l a t i v e activities determined. (2) T h e a c t i v i t y f a c t o r s h a v e c a l c u l a t e d o n t h e Q-e s c h e m e f o r v i n y l h y d r o quinonedibenzoate. Translated by V. ALFOI~D REFERENCES 1. H. G. CASSIDY, J. Amer. Chem. Soc. 71: 402, 1949 2. I. H. UPDEGRAFF and H. G. CASSIDY, J. Amer. Chem. Soc. 71 : 409, 1949 3. S. N. USHAKOV, O. M. KLIMOVA, O. S. KARCHMARCHIK and E. M. SMUL'SKAYA, Dokl. Akad. l~auk SSSR 143: 231, 1962 4. H. KAMAGAVA and H. G. CASSlDY, J. Polymer Sci. A. I, 1: 1971, 1963 5. T. ALFREY, J. BORER and H. MARK, Copolymerization. Izd. in. lit. 1953 6. E. C. CHAPIN, G. E. HAM a n d C. K. MILLS, J. Polymer Sci. 4: 597, 1949 7. F. R. MAYO a n d F. M. LEWIS, J. Amer. Chem. See. 66: 1594, 1944 8. H. G. CASSIDY, M. EZRIN and I. H. UPDEGRAFF, J. Araer. Chem. See. 75: 1615, 1953
CONDUCTIVITY OF POLYMER FILMS AT HIGH FREQUENCIES* L . I . ] 3 0 G U S L A V S K I I a n d L. S. S T I L B A N S I n s t i t u t e of Electrochemistry, U.S.S.R. A c a d e m y of Sciences
(Received 4 December 1963) WHEN the conductivity of films of the polymer complex tetracyanoethylene (TCE) on different metals was investigated, it was found that the capacitance a n d r e s i s t i v i t y o f t h e s e f i l m s d e p e n d o n t h e f r e q u e n c y [1, 2] b u t t h e r e s u l t s a r e r e s t r i c t e d t o a s m a l l r a n g e o f f r e q u e n c i e s f r o m 0 t o 0.2 Mc/s. I n t h e p r e s e n t w o r k w e h a v e s t u d i e d t h e c o n d u c t i v i t y o f f i l m s i n a f r e q u e n c y r a n g e o f 0.5 t o 200 Yfc/s.
EXPERIMENTAL The specimens studied were a polymeric complex of TOE with silver, and also films of a metal-free polymer. The latter were prepared at two extreme temperatures, 300 ° which is the m i n i m u m for the formation of a metal-free polymer on mica, glass or quartz; and 500 ° where the film is no longer subject to t o t a l degradation, and m a y be more ordered t h a n in the first case. The base used was mica 3 m m thick, the pieces being cut in such a way as to correspond exactly with the terminals of the Q-meters KV-1 and UK-1. * Vysokomol. soyed. 6: No. 10, 1802-1805, 1964.
Conductivity of polymer films
1997
The method of preparing the polymeric films was briefly as follows. To prepare films with complex-bound silver a layer of silver about 10 -5 cm thick was sprayed on to mica flakes. Then the flakes were treated in TCE vapours in ampoules which had first been evacuated, at 300 and 500°'for 10 hr. The TCE reacted with the sprayed silver layer to form a polymer containing complex-bonded silver. To prepare the polytetracyanoethylene films, the bases were treated without the sprayed metal in TCE vapours. The TCE then was polymerized on the surface of the mica to form a metal-free polymer. For the measurements on the mica flakes coated with polymer, contacts were deposited by spraying silver, or by depositing a layer of silver paste in such a way that measurements could be made over an area 1-3 m m wide and 15 m m long. The depth of the film was found b y weighing the plates before and after the filming. Variation in the weight was 2-3 × 10 -4 g, and the accuracy of the determination was 10 -5 g. The depth of the metal-free film was 5 x l0 -~ cm, and that of the film of polymer complex with silver was 6.4 × 10 -s cm. To study the resistivity of the specimens as a function of temperature, we used beam heating b y means of an illuminator. The resistivity and activation energy of conductivity with DC were measure in a vacuum at 20-300 °. The activation energy of the conductivity was determined with an accuracy of up to 10%. I t was found impossible to study the specimens i n vacuo in the entire frequency range due to distortions in the cell. When the resistivity measured made i n vacuo were compared with those obtained in air it was found that the air only affects measurements made with DC, and in the sonic frequency range below 50 ke/s, The active component of the total resistivity was calculated with the formula [3] R = Q 1 Q 2 / ( w G ( Q 1 - Q 2 ) ),
where Q~ is the Q of the mica specimen without a film, Q~ that of the specimen with a polymeric complex film, w the angular frequency and G the initial capacitance found from the readings of the Q capacitance meter. To find out whether the effect obtained could not be due to the distributed capacitance of the specimen, the gap between the electrodes in one of the specimens of film on glass, was varied from 2.3 to 7-2 ram. The resistivity measured at frequency of 200 Mc/s then increased from 3.14 × 105 to 9.7 × 105 ohms. This means that the measurements did actually depend on the resistivity of the films. F i g u r e 1 s h o w s t h e r e s i s t i v i t y of a m e t a l - f r e e film as a f u n c t i o n of t h e freq u e n c y for t w o s p e c i m e n s m a d e a t 300 a n d 500 ° . I t is e v i d e n t ( c u r v e 2) t h a t of t h e film p r e p a r e d a t 500 ° is n o t d e p e n d e n t o n t h e f r e q u e n c y e v e n a t 10 Me/s, w h i l e t h e r e s i s t i v i t y of t h e f i h n p r e p a r e d a t 300 ° ( c u r v e 1) v a r i e s i n t h e e n t i r e f r e q u e n c y range. W h e n the f r e q u e n c y was increased the difference in the resistivi t y of t h e t w o s p e c i m e n s d i m i n i s h e d . As i n t h e case of t h e m e t a l - f r e e p o l y m e r s , t h e r e s i s i t i v i t y of a film c o n s i s t i n g o f t h e p o l y m e r i c c o m p l e x T C E w i t h s i l v e r fell as t h e f r e q u e n c y rose, a n d w a s i n d e p e n d e n t a t 10 Mc/s. F o r t h e films of t h e m e t a l - f r e e p o l y m e r t h e a c t i v a t i o ~ e n e r g y of t h e c o n d u c t i v i t y a t 300 ° w a s 0.53 eV, a n d 0.26 eV a t 500 °. I t is i n t e r e s t i n g t o c o m p a r e t h e a c t i v a t i o n e n e r g i e s of t h e c o n d u c t i v i t y of the same specimens at different frequencies. F i g u r e 2 shows t h i s for t h e m e t a l - f r e e film a t 500 ° i n t h e t e m p e r a t u r e r a n g e f r o m 20 t o - - 7 0 ') as a f u n c t i o n of t h e f r e q u e n c y . F o r films of t h e p o l y m e r i c T C E c o m p l e x w i t h s i l v e r we c o m p a r e d t h e t h e r m a l a c t i v a t i o n e n e r g i e s of c o n d u c t i v i t y m e a s u r e d o n d i r e c t c u r r e n t a n d i n t h e p l a t e a u r a n g e ( a t 35 Me/s). I n t h e t e m p e r a t u r e r a n g e 2 0 - 1 2 0 ° t h e a c t i v a t i o n e n e r g y of c o n d u c t i v i t y falls f r o m 0-20 t o 0.07 eV.
1998
L . I . BOGUSLAVsKn a n d L . S. STILBANS
We also measured the thermo-e.m.f, of the metal-free film prepared at 500 °. Judging from the sign of the thermo-e.m.f., the film has n-type conductivity. For this film the thermo-e.m.f, is almost independent of temperature between 20 and 300 °, and the magnitude is 60-70 mV/°. In Shelykh's a t t e m p t to measure the Hall effect, the Hall mobility was found to be less than 0.005 V" cm/°.
~E~v
71
1~
005
8
logu
5 0 FIG. 1.
I
100
Mc/s
200
FIG. 2.
FIG. 1. R e s i s t i v i t y o f m e t a l - f r e e p o l y m e r i c film as a f u n c t i o n o f t h e f r e q u e n c y a t 20°: / - - s p e c i m e n p r e p a r e d a t 300°; 2 - - a t 500 °. FIG. 2. T h e r m a l a c t i v a t i o n e n e r g y o f t h e c o n d u c t i v i t y o f a m e t a l - f r e e p o l y m e r i c film as a f u n c t i o n of f r e q u e n c y ( l o w - t e m p e r a t u r e p a r t o f t h e curve). T h e s p e c i m e n was p r e p a r e d a t 500 ° .
Generally speaking, the results can be dealt with b y using free variation of the model there being no clearly defined boundary between them. The first of these involves point impurity centres in a certain continuum, which corresponds to the model used for the impurity conductivity in germanium and silicon [5, 6]. In this model the frequency characteristics of the active and reactive components are directly related to the frequencies of the carrier jumps between impurity centres, the most probable distance between the centres being found from the frequency dependencies [6]. When the variable field of this frequency is applied, so that the carrier cannot make relaxation oscillations after the film, this process appears as the reactive component of the current. This vibration cannot follow the film the active component of the current appears, with zero activation energy. Now let us imagine that instead of point impurities, we have impurities separated b y a distance rather less than their size. In this case it is quite naturally to turn over to the heterogeneous model used for the case of organic semiconductors in a number of works, [1] for instance. In view of the concrete structure it is suggested that the relaxation vibrations of the carrier take place in the range of continuously conjugated regions, while the mean distance between these regions and their actual size can be found from the frequency dependencies and the v.a. characteristics [1].
Conductivity of polymer films
1999
Finally, in the third modification of the model it is assumed ~hat the distance between "impurities" is commensurate with their actual size. This corresponds to regions of continuous conjugation separated by thick barriers. In this case the interlayers will be short circuited at exceedingly high frequencies, and allowance must be made for the fact that, beginning at a certain frequency, in the half life period the electrons will not be able to cover the distance between the continuously conjugate regions. In particular it must be noted t h a t the structural heterogeneity observed is not only trivial evidence of the imperfection of the material, as can be seen at first glance. Even for an ordered structure when the size of the molecules approaches a sub-phase, the role of the contact effect associated with the "surface" of the continuously conjugated region increases, which can be seen from the close dependence of the electrical properties of the gas adsorption, and also by the frequency characteristics. In particular, the fact t h a t oxygen only affects the electronical conductivity in the sonic frequency range shows t h a t the barriers formed at the interface due to oxygen adsorption are extremely thin, and as the frequency rises t h e y are unable to exert any influence on the passage of the current. For the first modification the true mobility could be found by using the conductivity measured with direct current. I n the latter case, to find the " t r u e " mobility which would correspond to carrier movement in the region of co~ltinuous conjugation the conductivity measurements used would have to have been taken in alternating current in the plateau region. I n practice, a polymer appears to be a collection of macromQlecules of different length, as we can see from the absorption spectra of the films. The shortest macromolecules are acceptors in respect of the longer, which follows from the findings of a stud)" of the work function of electrons of these materials when heated*. Thus we have a material continuously composed of impurities of both donor and acceptor type. An increase in temperature will increase the jump frequency of the carriers taking the current to the system consisting continuously o f " i m p u r i t i e s " . A peculiar feature of this kind of " i m p u r i t y " is t h a t t h e y have a large number of carriers which are only free inside macromolecnies, which can nevertheless be detected by measurements made with alternating current. The results of this work force the conclusion t h a t direct current measurements cannot give a single picture of the mechanism of conductivity, which appears to consist of two mechanisms: transfer of carriers from one continuously conjugated region to another, and conductivity inside the regions themselves, for which the activation energies are approximately zero for the materials studied. CONCLUSIONS
The resistivity and activatior~ energy of the conductivity of films of the polymeric complex tetracyanoethylene diminish as the frequency rises. Analysis * An article will be published on this question later.
2000
YE. I. KLABUXOVSKIIet al.
of the curves for the resistivity as a function of frequency, which have a range independent of frequency, together with comparison of the activation energies of the conductivity found with direct current and high frequency, suggest t h a t allowance must be made for the barriers between macromolecules when dealing with the processes of conductivity in organic polymeric materials. Translated by V. ALFORD
REFERENCES
1. L. I. BOGUSLAVSKII and L. S. STILBANS, I)okl. Akad. Nauk SSSR 147: 1114, 1962 2. L. I. BOGUSLAVSKII, A. I. SHERLE and A. A. BERLIN, Zh. fiz. khim. 38: 1126, 1964 3. K. S. PULULYAKH, Elektronnye rezonansnye izmeritel'n pribory. (Electron Resonance Measuring Instruments.) Izd. Khar'kov University, 1961 4. C. M. HUGGINS and A. H. SHARBAUGH, g. Chem. Phys. 38: 393, 1963 5. M. POLLAK and T. H. GEBALLE, Phys. Rev. 122: 742, 1961 6. S. TANAKA and H. V. FAN. Phys. Rev. 132: 1516, 1963
S T R U C T U R E OF O P T I C A L L Y A C T I V E P O L Y M E R S F R O M E S T E R S OF M E T H A C R Y L I C A N D ITACONIC ACIDS* YE. I. KLABUNOVSKII, B. V. LOPATIN, L. G. VORONTSOVA, YU. I. PETROV and M. I. SttVARTSMAN The N. D. Zelinskii Institute of Organic Chemistry, U.S.S.R. Academy of Sciences (Received 6 December 1963)
POLYMERS prepared under the conditions of anionic polymerization usually have more stereoregular structures t h a n those formed b y means of free radical initiators. The difference is also seen b y the appearance of a crystalline phase in the anionic polymers. B u t if appropriate measures are not t aken during their formation, the anionic polymers (lower polyalkylmethacrylates for instance) prepared in the amorphous state will still have I R spectra different from those of radical polymers [1-12]. I t is interesting to make a comparison of I R and X - r a y diffraction studies of structure of optically active polymers prepared under different conditions. To this end we prepared polymers of ( + ) - 2 - m e t h y l b u t y l m e t h a c r y l a t e , (--)-met h y l m e t h a c r y l a t e and (A-)-di-(2)mcthylbutyl-itaeonate under the conditions of anionic, radical and thermal polymerization, and studied their structures. To simplify the problem of comparison, no special measures were taken to produce polymers in the crystalline state. * Vysokomol. soyed. 6: No. 10, 1806-1809, 1964.
L . I . BOGUSLAVSKIIand L. S. STILBANS
CONCLUSIONS (1) V i n y l h y d r o q n i n o n e d i b e n z o a t e h a s b e e n c o p o l y m e r i z e d w i t h a c r y l i c a n d m e t h a c r y l i c a c i d i n t h e p r e s e n c e o f a z o b i s i s o b u t y r o r t i t r i l e a t 60 °, a n d t h e r e l a t i v e activities determined. (2) T h e a c t i v i t y f a c t o r s h a v e c a l c u l a t e d o n t h e Q-e s c h e m e f o r v i n y l h y d r o quinonedibenzoate. Translated by V. ALFOI~D REFERENCES 1. H. G. CASSIDY, J. Amer. Chem. Soc. 71: 402, 1949 2. I. H. UPDEGRAFF and H. G. CASSIDY, J. Amer. Chem. Soc. 71 : 409, 1949 3. S. N. USHAKOV, O. M. KLIMOVA, O. S. KARCHMARCHIK and E. M. SMUL'SKAYA, Dokl. Akad. l~auk SSSR 143: 231, 1962 4. H. KAMAGAVA and H. G. CASSlDY, J. Polymer Sci. A. I, 1: 1971, 1963 5. T. ALFREY, J. BORER and H. MARK, Copolymerization. Izd. in. lit. 1953 6. E. C. CHAPIN, G. E. HAM a n d C. K. MILLS, J. Polymer Sci. 4: 597, 1949 7. F. R. MAYO a n d F. M. LEWIS, J. Amer. Chem. See. 66: 1594, 1944 8. H. G. CASSIDY, M. EZRIN and I. H. UPDEGRAFF, J. Araer. Chem. See. 75: 1615, 1953
CONDUCTIVITY OF POLYMER FILMS AT HIGH FREQUENCIES* L . I . ] 3 0 G U S L A V S K I I a n d L. S. S T I L B A N S I n s t i t u t e of Electrochemistry, U.S.S.R. A c a d e m y of Sciences
(Received 4 December 1963) WHEN the conductivity of films of the polymer complex tetracyanoethylene (TCE) on different metals was investigated, it was found that the capacitance a n d r e s i s t i v i t y o f t h e s e f i l m s d e p e n d o n t h e f r e q u e n c y [1, 2] b u t t h e r e s u l t s a r e r e s t r i c t e d t o a s m a l l r a n g e o f f r e q u e n c i e s f r o m 0 t o 0.2 Mc/s. I n t h e p r e s e n t w o r k w e h a v e s t u d i e d t h e c o n d u c t i v i t y o f f i l m s i n a f r e q u e n c y r a n g e o f 0.5 t o 200 Yfc/s.
EXPERIMENTAL The specimens studied were a polymeric complex of TOE with silver, and also films of a metal-free polymer. The latter were prepared at two extreme temperatures, 300 ° which is the m i n i m u m for the formation of a metal-free polymer on mica, glass or quartz; and 500 ° where the film is no longer subject to t o t a l degradation, and m a y be more ordered t h a n in the first case. The base used was mica 3 m m thick, the pieces being cut in such a way as to correspond exactly with the terminals of the Q-meters KV-1 and UK-1. * Vysokomol. soyed. 6: No. 10, 1802-1805, 1964.
Conductivity of polymer films
1997
The method of preparing the polymeric films was briefly as follows. To prepare films with complex-bound silver a layer of silver about 10 -5 cm thick was sprayed on to mica flakes. Then the flakes were treated in TCE vapours in ampoules which had first been evacuated, at 300 and 500°'for 10 hr. The TCE reacted with the sprayed silver layer to form a polymer containing complex-bonded silver. To prepare the polytetracyanoethylene films, the bases were treated without the sprayed metal in TCE vapours. The TCE then was polymerized on the surface of the mica to form a metal-free polymer. For the measurements on the mica flakes coated with polymer, contacts were deposited by spraying silver, or by depositing a layer of silver paste in such a way that measurements could be made over an area 1-3 m m wide and 15 m m long. The depth of the film was found b y weighing the plates before and after the filming. Variation in the weight was 2-3 × 10 -4 g, and the accuracy of the determination was 10 -5 g. The depth of the metal-free film was 5 x l0 -~ cm, and that of the film of polymer complex with silver was 6.4 × 10 -s cm. To study the resistivity of the specimens as a function of temperature, we used beam heating b y means of an illuminator. The resistivity and activation energy of conductivity with DC were measure in a vacuum at 20-300 °. The activation energy of the conductivity was determined with an accuracy of up to 10%. I t was found impossible to study the specimens i n vacuo in the entire frequency range due to distortions in the cell. When the resistivity measured made i n vacuo were compared with those obtained in air it was found that the air only affects measurements made with DC, and in the sonic frequency range below 50 ke/s, The active component of the total resistivity was calculated with the formula [3] R = Q 1 Q 2 / ( w G ( Q 1 - Q 2 ) ),
where Q~ is the Q of the mica specimen without a film, Q~ that of the specimen with a polymeric complex film, w the angular frequency and G the initial capacitance found from the readings of the Q capacitance meter. To find out whether the effect obtained could not be due to the distributed capacitance of the specimen, the gap between the electrodes in one of the specimens of film on glass, was varied from 2.3 to 7-2 ram. The resistivity measured at frequency of 200 Mc/s then increased from 3.14 × 105 to 9.7 × 105 ohms. This means that the measurements did actually depend on the resistivity of the films. F i g u r e 1 s h o w s t h e r e s i s t i v i t y of a m e t a l - f r e e film as a f u n c t i o n of t h e freq u e n c y for t w o s p e c i m e n s m a d e a t 300 a n d 500 ° . I t is e v i d e n t ( c u r v e 2) t h a t of t h e film p r e p a r e d a t 500 ° is n o t d e p e n d e n t o n t h e f r e q u e n c y e v e n a t 10 Me/s, w h i l e t h e r e s i s t i v i t y of t h e f i h n p r e p a r e d a t 300 ° ( c u r v e 1) v a r i e s i n t h e e n t i r e f r e q u e n c y range. W h e n the f r e q u e n c y was increased the difference in the resistivi t y of t h e t w o s p e c i m e n s d i m i n i s h e d . As i n t h e case of t h e m e t a l - f r e e p o l y m e r s , t h e r e s i s i t i v i t y of a film c o n s i s t i n g o f t h e p o l y m e r i c c o m p l e x T C E w i t h s i l v e r fell as t h e f r e q u e n c y rose, a n d w a s i n d e p e n d e n t a t 10 Mc/s. F o r t h e films of t h e m e t a l - f r e e p o l y m e r t h e a c t i v a t i o ~ e n e r g y of t h e c o n d u c t i v i t y a t 300 ° w a s 0.53 eV, a n d 0.26 eV a t 500 °. I t is i n t e r e s t i n g t o c o m p a r e t h e a c t i v a t i o n e n e r g i e s of t h e c o n d u c t i v i t y of the same specimens at different frequencies. F i g u r e 2 shows t h i s for t h e m e t a l - f r e e film a t 500 ° i n t h e t e m p e r a t u r e r a n g e f r o m 20 t o - - 7 0 ') as a f u n c t i o n of t h e f r e q u e n c y . F o r films of t h e p o l y m e r i c T C E c o m p l e x w i t h s i l v e r we c o m p a r e d t h e t h e r m a l a c t i v a t i o n e n e r g i e s of c o n d u c t i v i t y m e a s u r e d o n d i r e c t c u r r e n t a n d i n t h e p l a t e a u r a n g e ( a t 35 Me/s). I n t h e t e m p e r a t u r e r a n g e 2 0 - 1 2 0 ° t h e a c t i v a t i o n e n e r g y of c o n d u c t i v i t y falls f r o m 0-20 t o 0.07 eV.
1998
L . I . BOGUSLAVsKn a n d L . S. STILBANS
We also measured the thermo-e.m.f, of the metal-free film prepared at 500 °. Judging from the sign of the thermo-e.m.f., the film has n-type conductivity. For this film the thermo-e.m.f, is almost independent of temperature between 20 and 300 °, and the magnitude is 60-70 mV/°. In Shelykh's a t t e m p t to measure the Hall effect, the Hall mobility was found to be less than 0.005 V" cm/°.
~E~v
71
1~
005
8
logu
5 0 FIG. 1.
I
100
Mc/s
200
FIG. 2.
FIG. 1. R e s i s t i v i t y o f m e t a l - f r e e p o l y m e r i c film as a f u n c t i o n o f t h e f r e q u e n c y a t 20°: / - - s p e c i m e n p r e p a r e d a t 300°; 2 - - a t 500 °. FIG. 2. T h e r m a l a c t i v a t i o n e n e r g y o f t h e c o n d u c t i v i t y o f a m e t a l - f r e e p o l y m e r i c film as a f u n c t i o n of f r e q u e n c y ( l o w - t e m p e r a t u r e p a r t o f t h e curve). T h e s p e c i m e n was p r e p a r e d a t 500 ° .
Generally speaking, the results can be dealt with b y using free variation of the model there being no clearly defined boundary between them. The first of these involves point impurity centres in a certain continuum, which corresponds to the model used for the impurity conductivity in germanium and silicon [5, 6]. In this model the frequency characteristics of the active and reactive components are directly related to the frequencies of the carrier jumps between impurity centres, the most probable distance between the centres being found from the frequency dependencies [6]. When the variable field of this frequency is applied, so that the carrier cannot make relaxation oscillations after the film, this process appears as the reactive component of the current. This vibration cannot follow the film the active component of the current appears, with zero activation energy. Now let us imagine that instead of point impurities, we have impurities separated b y a distance rather less than their size. In this case it is quite naturally to turn over to the heterogeneous model used for the case of organic semiconductors in a number of works, [1] for instance. In view of the concrete structure it is suggested that the relaxation vibrations of the carrier take place in the range of continuously conjugated regions, while the mean distance between these regions and their actual size can be found from the frequency dependencies and the v.a. characteristics [1].
Conductivity of polymer films
1999
Finally, in the third modification of the model it is assumed ~hat the distance between "impurities" is commensurate with their actual size. This corresponds to regions of continuous conjugation separated by thick barriers. In this case the interlayers will be short circuited at exceedingly high frequencies, and allowance must be made for the fact that, beginning at a certain frequency, in the half life period the electrons will not be able to cover the distance between the continuously conjugate regions. In particular it must be noted t h a t the structural heterogeneity observed is not only trivial evidence of the imperfection of the material, as can be seen at first glance. Even for an ordered structure when the size of the molecules approaches a sub-phase, the role of the contact effect associated with the "surface" of the continuously conjugated region increases, which can be seen from the close dependence of the electrical properties of the gas adsorption, and also by the frequency characteristics. In particular, the fact t h a t oxygen only affects the electronical conductivity in the sonic frequency range shows t h a t the barriers formed at the interface due to oxygen adsorption are extremely thin, and as the frequency rises t h e y are unable to exert any influence on the passage of the current. For the first modification the true mobility could be found by using the conductivity measured with direct current. I n the latter case, to find the " t r u e " mobility which would correspond to carrier movement in the region of co~ltinuous conjugation the conductivity measurements used would have to have been taken in alternating current in the plateau region. I n practice, a polymer appears to be a collection of macromQlecules of different length, as we can see from the absorption spectra of the films. The shortest macromolecules are acceptors in respect of the longer, which follows from the findings of a stud)" of the work function of electrons of these materials when heated*. Thus we have a material continuously composed of impurities of both donor and acceptor type. An increase in temperature will increase the jump frequency of the carriers taking the current to the system consisting continuously o f " i m p u r i t i e s " . A peculiar feature of this kind of " i m p u r i t y " is t h a t t h e y have a large number of carriers which are only free inside macromolecnies, which can nevertheless be detected by measurements made with alternating current. The results of this work force the conclusion t h a t direct current measurements cannot give a single picture of the mechanism of conductivity, which appears to consist of two mechanisms: transfer of carriers from one continuously conjugated region to another, and conductivity inside the regions themselves, for which the activation energies are approximately zero for the materials studied. CONCLUSIONS
The resistivity and activatior~ energy of the conductivity of films of the polymeric complex tetracyanoethylene diminish as the frequency rises. Analysis * An article will be published on this question later.
2000
YE. I. KLABUXOVSKIIet al.
of the curves for the resistivity as a function of frequency, which have a range independent of frequency, together with comparison of the activation energies of the conductivity found with direct current and high frequency, suggest t h a t allowance must be made for the barriers between macromolecules when dealing with the processes of conductivity in organic polymeric materials. Translated by V. ALFORD
REFERENCES
1. L. I. BOGUSLAVSKII and L. S. STILBANS, I)okl. Akad. Nauk SSSR 147: 1114, 1962 2. L. I. BOGUSLAVSKII, A. I. SHERLE and A. A. BERLIN, Zh. fiz. khim. 38: 1126, 1964 3. K. S. PULULYAKH, Elektronnye rezonansnye izmeritel'n pribory. (Electron Resonance Measuring Instruments.) Izd. Khar'kov University, 1961 4. C. M. HUGGINS and A. H. SHARBAUGH, g. Chem. Phys. 38: 393, 1963 5. M. POLLAK and T. H. GEBALLE, Phys. Rev. 122: 742, 1961 6. S. TANAKA and H. V. FAN. Phys. Rev. 132: 1516, 1963
S T R U C T U R E OF O P T I C A L L Y A C T I V E P O L Y M E R S F R O M E S T E R S OF M E T H A C R Y L I C A N D ITACONIC ACIDS* YE. I. KLABUNOVSKII, B. V. LOPATIN, L. G. VORONTSOVA, YU. I. PETROV and M. I. SttVARTSMAN The N. D. Zelinskii Institute of Organic Chemistry, U.S.S.R. Academy of Sciences (Received 6 December 1963)
POLYMERS prepared under the conditions of anionic polymerization usually have more stereoregular structures t h a n those formed b y means of free radical initiators. The difference is also seen b y the appearance of a crystalline phase in the anionic polymers. B u t if appropriate measures are not t aken during their formation, the anionic polymers (lower polyalkylmethacrylates for instance) prepared in the amorphous state will still have I R spectra different from those of radical polymers [1-12]. I t is interesting to make a comparison of I R and X - r a y diffraction studies of structure of optically active polymers prepared under different conditions. To this end we prepared polymers of ( + ) - 2 - m e t h y l b u t y l m e t h a c r y l a t e , (--)-met h y l m e t h a c r y l a t e and (A-)-di-(2)mcthylbutyl-itaeonate under the conditions of anionic, radical and thermal polymerization, and studied their structures. To simplify the problem of comparison, no special measures were taken to produce polymers in the crystalline state. * Vysokomol. soyed. 6: No. 10, 1806-1809, 1964.