- Email: [email protected]
A new highly conductive polymer complex based on aniline
Polymer Science U.S.S.R. Vol. 31, No. 9, pp. 2148-2153, 1989 ]~'inted in Poland
0032-3950189 $10.00+.00 ~) 1990 Pergamon Pre8 ple
A NEW HIGHLY CONDUCTIVE POLYMER COMPLEX BASED ON ANILINE* A. M. ARZUMANYAN, S. G. GRIGORYAN, G. V. MARTIROSYAN and A. A. MATNISHYAN Armyansk Branch, All-Union Scientific Research Institute for Reagents and Especially Pure Chemical Substances (Received 2 March 1988) A soluble polyaniline complex with iodine having semiconductor properties and a specific ,lectrical conductivity of 10-*-10 -3 ohm-1/cm is synthesized, and the synthesis characteristics and structure of the complex are studied. It is shown that chain growth in position 4 relative to the ring nitrogen atom is the main polymerization direction. Depending on its iodine content, the polymer can be in the form of an anion 13 or can form long polyiodoiodate chains. Two forms of polymer are observed, i.e. a highly doped (conducting) form, which is related to the formation of quaternary ammonium salts, and an undoped, dielectric form.
EVEN during the last century aniline black attracted the attention of research workers as a dyestuff, and today it is a promising material for electronics. Oxidative dehydropolycondensation of aniline in the presence of bichromate [1], persulphate [2], Berthollet's salt [3], or by electrochemical oxidation [4] have been used to prepare polymers of specific electrical conductivity tr20 = 10- is-10- lcm- 1/ohm. However, the chemistry of oxidation and the structure of these polymers have not yet been elucidated. As was shown earlier, iodine is an effective catalyst fbr the polymerization of aromatic [5] and heteroaromadc [6] compounds. The polymer complexes obtained have semiconductor properties, and depending on the iodine content, their specific electrical conductivities can be varied from 10 -11 to 10 -3 ohm-1/cm. This work is concerned with studying the laws of synthesis, the structure, and the properties of a polyaniline complex (PANC). The polymer was synthesized by heating aniline in the presence of iodine and subsequent purification of the complex formed by Soxhlet extraction. Apart from PANC, an anilinohydrate, formed as a result of competing reactions, could be separated from the reaction mass and identified. Increase in iodine concentration (above the molar ratio aniline : iodine= 1 : 1.75) results in a decrease in yield of the PANC, whereas the yield of the anilinohydrate increases (Fig. 1). A control test showed that the anilinohydrate is not thermally polymerized up to 250°C, and consequently it is not an intermediate. In this process the iodine plays a multi-functional part. At the beginning of the process the aniline, and also many aromatic compounds [7] form a charge transfer complex with the iodine, with polarization of the C - H and N - H bonds; on heating the complex thus formed in an iodine medium the iodine acts as a catalyst for oxidative dehydropolycondensation. The HI released as a result of the reaction reacts with the polyaniline formed, and gives the polyhydrate form. * Vysokomol. soyed. A31: No. 9, 1950-1954, 1989. 2148
New highly conductive polymer complex based on aniline
2149
Increase in the synthesis temperature above 175°C results in a fall in the PANC yield (Fig. 2), whereas polymer degradation, according to T G A data, begins only at 250°C. The decrease in PANC yield is probably associated with rupture o[ the active complex between aniline and iodine.
Yleid %
Yield, % 70
3O
30
e'l"---
"
1 1
0.5
150
l.O Z2, moles
_
l
250
1
350 T°
Flo. 1 FIO. 2 FIG. I. Yield of PANC (1) and aniline iodohydrate (2) as a function of iodine concentration. T=175°C, z = 2 hr. FIG. 2. Yield of PANC as a function of temperature. Here and in Fig. 3 T=2 hr, molar ratio iodine : aniline=0.75 : 1. The iodine content of the polymer is almost independent of the synthesis temperature (Fig. 3) and is 52-60%, which corresponds to the composition (PANC)I.0Ios-1.1. On alkali treatment of PANC the iodine content in the polymer can be decreased to 32Yo, and formation of a fraction insoluble in D M F A is observed. The process is almost complete after 2 hr, and further heating of the reaction mass does not increase the yield (Fig. 4), and results in no significant structural changes.
Yield. % 60 -
_-re,%
qO qO
20 ]
200
I
300 T o
o/-
--
/ l
3
1
7 "-'h'. %,,
FIG. 3 FIG. 4 FIG. 3. Iodine content of PANC as a function of polymerization temperature. FIG. 4. Yield of PANC as a function of process time. T = 175°C, molar ratio iodine : aniliner0.75 : 1. C o m p a r i s o n o f the I R s p e c t r a o f P A N C with aniline b l a c k o b t a i n e d as d e s c r i b e d b y P a r i n i et al. [1] r e v e a l e d significant s t r u c t u r a l difference (Fig. 5). Skeletal p l a n a r v i b r a t i o n s o f the C = C b o n d o f the c o n j u g a t e d a r o m a t i c r i n g a r e o b s e r v e d in the 1R s p e c t r u m o f P A N C in the r e g i o n o f 1560 c m -a (1600 c m - 1 in aniline), a n d also very w e a k a b s o r p t i o n o f the u n c o n j u g a t e d a r o m a t i c ring in the r e g i o n o f 1500 c m -1. I n
A. M. ARZU~NYAN et aL
2150
~o
33
27
71
15
.9 v, am-I
FIO. 5. IR spectra of PANC (1) and aniline black (2). view of the low molecular mass (2000) the proportion of end groups is fairly high, amounting to 20 Yo, as result of which extra-planar deformational vibrations o f the C - H bond of the monosubstituted aromatic ring are observed in the IR spectrum in the region of 690 and 740 c m , 1. Growth of the polymer chain occurs mainly at positions 4 and 3-5 relative to the ring nitrogen atom. This is shown by the presence in the IR spectrum of characteristic deformational vibrations of the 1,4- and 1,3,5substituted aromatic rings in the region of 1090, 1160, and 1110 era-1.
II
o,7.
'
+NH3 '
In-
il
NH~ ' I
7~
-
III
The wide absorption (2800-3100 cm-1) with a maximum in the region of 2960 cm-1 is due to the NH~ group, and absorption characteristic of the NH + is observed in the region of 2588 cm-1 [8]. These data indicate the presence of the polyhydrate form in the polymer, and the presence of wide band absorption (3400-3650) with a maximum in the region of 3500 cm -1, which is characteristic of the NH bond of both primary and secondary amines, can indicate that not all the polymer chain units form the salt form. The absorpt!on band in the region of 1620 cm -1 is obviously associated with deformational vibrations of the NH bond of the iodohydrates, similar to the absorption obseIved with hydrochloride [8]. Structure III can be formed as a result of further oxidation under reaction conditions similar to those for aniline black [9]. To obtain a quantitative evaluation of the structural units I and II dimethylaniline was used as a model, the polymerization of which at positions 4 relative to the ring nitrogen atom is almost eliminated. As would be expected, the yield of polydimethyl,
New highly conductive polymer complex based on aniline
2151
aniline is very low, amounting to 6-8 ~o. Consequently (provided it is assumed that the polymerization of dimethylaniline occurs at positions 3 and 5) growth of the PANC chain occurs mainly at position 4 relative to the ring nitrogen atom. Allowing for the yields of PANC and polydimethylaniline, the proportion of polymer units of structure ] amounts to 10-12~o. On iodination, polycyclic aromatic compounds form small chain polyidoiodates [10], the nature of which has not yet been finally established, although Marks and Kalina [11] suggested that I7 ions are present. Investigation of the UV spectra of PANC showed tlaat in the region of 295 nm absorption occurs corresponding to the I~ anion [12], and the maxima in the region of 520, 550, 600, and 655 cm- 1 indicate the presence of long polyiodoiodate chains (Fig. 6) [13]. On decreasing the iodine content of the polymer 23 70
\ -- \
jf-~\
\\ \
I
ao
I
l
200
400
1
I
BOO 800 ,Tt717177
FIG. 6. UV spectra of PANC, containing 56 (1) and 32y0 iodine (2).
by alkali treatment the intensities of absorption of the polyiodoiodate forms are decreased, with a simultaneous increase in concentration of the I~ anions. Moreover, some hypsochromic shifts in the positions of the above maxima are observed (480, 550, 580 and 650), which also indicates a decrease in length of the polyiodoiodate chain on decreasing the iodine content of the polymer. The polymer PANC is a black powder, completely soluble in DMFA and partially (50 ~o) in chloroform. The specific electrical conductivity of specimen I, which contains 56~o iodine, is a2o=3.8 × 10 -3 ohrn-1/cm, and of specimen II, which contains 3 2 ~ iodine, a2o=7.3 x 10 -4 ohm-1/cm. The polymer is paramagnetic: the concentration of paramagnetic centres in specimen I is 2 x 1018 spin/g, width 0.9 roT, and of specimen II 8x10 is spin/g, width 0.9 mT. With increase in iodine concentration the intensity of the ESR signal falls, which is associated with disturbance of the conjugation by complex formation. The ESR spectrum of PANC consists of two narrow overlapping signals, which confirms the existence of the polymer in two forms, i.e. highly alloyed (conducting) and unalloyed (didectric). Similar phenomena have been observed by the present authors and by Matnishyan et aL [14] in the case of the polypyridine complex
2152
A.M.A.R-ARA.RA.RA.R~.s.NYANet al.
with iodine. The polymer P A N C is distinguished by its high stability in air: the iodine content is decreased by a mere 1-2 ~o over a year, and its specific electrical conductivity is almost unchanged over the same period. This polymer differs from known conducting p-type polymers in that the number o f electrons associated with the polymer chain is not changed during doping. Polymers with such a set of valuable properties can be used a s semiconductors. T h e polymerization method which we have considered also provides a means of obtaining a modified polymer of aniline black. On heating (150°C), in the presence of iodine, the aniline black fraction soluble in D M F A , the oligomer undergoes further polymerization, resulting in an increase in molecular weight, and the solubility in organic solvents is lost. The iodine content in the modified polymer is 5270, 0"20= 10 -4 o h m - I / c m . On alloying aniline black with gaseous H I the iodine content of the polymer is still higher than 6670, and a 2 0 = 2 x 10 - 4 o h m - I / s e e . As a result of electron donor interaction, strong phonon absorption, similar to aniline black, is observed in the I R ~pectra of the modified polymer and the polymer alloyed with HI, which hinders structural investigations o f these polymers. The IR spectra of the polymer specimen were obtained with a UR-20 spectrometer in thin films and in tablets with KBr, and the UV spectra were obtained with a "Speeord" spectrometer, chloroform as solvent, specimen concentration 10-3 mole/l. The ESR spectra were recorded with a "'E-3 Varian" instrument, using diphenylpicrylhydrazyl as standard. The dynamic TGA data were obtained with a Paulik-Paulik derivatograph, at a heating rate of 5 K/rain. The electrical conductivity of the polymer specimens, in the form of compacted tablets (pressure 150 x 105 PA) or films, was measured with a E6-13 terraohmeter. The molecular mass of the polymers was evaluated by a cryoseopic method in dioxane and by the Rast method in camphor. Pure, twice distilled aniline was used. The iodine was purified by sublimation. The aniline was polymerized in sealed, previously degassed ampouples (10 -2 mmHg) in an inert gas medium (argon or helium). In the ampoules was placed 0.93 g (0.01 mole) of aniline and from 0.63 g (0.0025 mole) to 3.8 g (0.015 mole) of iodine, and the ampoules were heated in a vertical furnace under dynamic conditions, i.e. 5 K/rain, until the required temperature was obtained (120300°C), and were then held at this temperature for 0.5 to 10 hr. The polymers were purified by Soxhlet ether extraction over 3-5 hr, and then by vacuum sublimation (1 mmHg) to constant weight, 10-407. (with respect to aniline) of the aniliniodohydrate being sublimated on the condenser, Tm,~--180"C (with decomposition). Found, 70:58"1 I, 6-1 N. Synthesis of aniliniodohydrate (for identification). A mixture of naphthalene or anthracene with iodine was heated to 140°C, the HI evolved on reaction was passed through a 25~/0solution of aniline in ether, and the residue of aniliniodohydrate deposited was washed with ether and dried, Tree= 180°C (with decomposition). Calculated, Yo: 57.03 I, 6.3 N. Found, ~o, 58.06 I, 6.8 N. The PANC was alkali treated with a concentrated KOH solution over 3-5 days at room temperature, and was then washed with distilled water and dried. The dimethylaniline was polymerized in sealed ampoules: 1.21 g (0"01 mole) of dimethylaniline and 1.26 g (0.005 mole) of iodine were heated at 1750C over 5 hr. The polymer was isolated by deposition from DMFA solution in water. The aniline black was heated in the presence of iodine in a sealed ampoule at 150°C over 2 hr. The aniline black was alloyed by passing gaseous HI through a layer of polymer over 2 hr. The polymers were purified by Soxhlet ether extraction and dried to constant weight under vacuum at 50°C. Translated by N. STANDEN
Modification of polyethylene surface sensitized with anthraquinone-9,10
2153
REFERENCES 1. V. P. PARINI, Z. S. KAZAKOVA and A. A. BERLIN, Vysokomol. soyed. 3: 1870, 1961 (Not translated in Polymer Sci. U.S.S.R.) 2. M. JOZEFOWICZ and G. BOLOGREJ, C. r. Acad. Sci. 260: 2037, 1965 3. J. LANGER, Solid State Commun. 26: 839, 1978 4. J. OHSAKA, Y. OHNUKI, M. OYAMA, G. KATAGIRU and K. KAMISAKO, S. Electroanal. Chem. 161: 399, 1984 5. A. A. MATNISHYAN, A. M. ARZUMANYAN, L. S. GRIGORYAN, I. L. ARUTYUNYAN, S. G. GR1GORYAN, R. S. ASATRYAN, A. L. MANUKYAN and R. O. MATEVOSYAN, Arm. khim. zh. 38: 590, 1985 6. A. A. MATNISHYAN, I. L. ARUTYUNYAN and A. M. ARZUMANYAN, Arm. khim. zh. 38: 728, 1985 7. B. TILGUIN and L. LAMBERTS, J. Phys. Chem. 84: 84, 1975 8. L. BELLAMY, Infakrasnye spektry slozhnykh molekul (Infrared Spectra of Complex Molecules). Moscow, 1963 9. A. G. MACDIARMID, J.-C. CHANG, W.-S. HUANG, A. F. RICHTER and A. I. EPSTEIN, Intern. Conf. on Science and Technology of Synthetic Metals Kyoto, 2, 1986 10. J. KOMMANDEUR and F. R. HALL, J. Chem. Phys. 34: 129, 1981 11. T. J. MARKS and D. W. KALINA, Extended Linear Chain Compounds 1: New York, 197, 1982 12. K. TOGODA and W. B. PERSON, J. Amer. Chem. Soc. 88: 1629, 1966 13. B. D. STEPIN and S. B. SPEPINA, Uspekhi khimii 55: 1434, 1986 14. A. A. MATNISHYAN, A. M. ARZUMANYAN and L. S. GRIGORYAN, Tez. Mezhdunar. konf. "Organicheskie materialy dlya elektroniki i priborostroeniya (Thesis of International Conference "Organic Materials for Electronics and Instrument Construction). Tashkent, 1987
Polymer Science U.~I.S.R. Vol. 31, No. 9, pp. 2153-2161, 1989 Printed in Poland
0032-3950189 $10.00+ .00 © 1990 Pergamon Pre~ pie
MODIFICATION OF A POLYETHYLENE SURFACE SENSITIZED WITH ANTHRAQUINONE-9,10 BY PHOTOOXIDATION. A KINETIC MODEL* A. A . DALINKEVICH, S. G . KIRYUSHKIN a n d Y u . A . SHLYAPNIKOV Institute of Chemical Physics, U.S.S.R. Academy of Sciences (Received 2 March 1988) A kinetic model for the photooxidative modification of PE in the presence of a sensitizer is proposed. The model takes into account the specific stages of polymer oxidation, degradation processes, taking place in the polymer, propagation of the oxidation chain along the macromolecule, and its transfer to an adjacent one. A decrease in the adhesional strength of the PE (strength of adhesional bonds) occurs as a result of degradation on repeated oxidation of * Vysokomol. soyed. A31: No. 9t 1955-1961, 1989.
0032-3950189 $10.00+.00 ~) 1990 Pergamon Pre8 ple
A NEW HIGHLY CONDUCTIVE POLYMER COMPLEX BASED ON ANILINE* A. M. ARZUMANYAN, S. G. GRIGORYAN, G. V. MARTIROSYAN and A. A. MATNISHYAN Armyansk Branch, All-Union Scientific Research Institute for Reagents and Especially Pure Chemical Substances (Received 2 March 1988) A soluble polyaniline complex with iodine having semiconductor properties and a specific ,lectrical conductivity of 10-*-10 -3 ohm-1/cm is synthesized, and the synthesis characteristics and structure of the complex are studied. It is shown that chain growth in position 4 relative to the ring nitrogen atom is the main polymerization direction. Depending on its iodine content, the polymer can be in the form of an anion 13 or can form long polyiodoiodate chains. Two forms of polymer are observed, i.e. a highly doped (conducting) form, which is related to the formation of quaternary ammonium salts, and an undoped, dielectric form.
EVEN during the last century aniline black attracted the attention of research workers as a dyestuff, and today it is a promising material for electronics. Oxidative dehydropolycondensation of aniline in the presence of bichromate [1], persulphate [2], Berthollet's salt [3], or by electrochemical oxidation [4] have been used to prepare polymers of specific electrical conductivity tr20 = 10- is-10- lcm- 1/ohm. However, the chemistry of oxidation and the structure of these polymers have not yet been elucidated. As was shown earlier, iodine is an effective catalyst fbr the polymerization of aromatic [5] and heteroaromadc [6] compounds. The polymer complexes obtained have semiconductor properties, and depending on the iodine content, their specific electrical conductivities can be varied from 10 -11 to 10 -3 ohm-1/cm. This work is concerned with studying the laws of synthesis, the structure, and the properties of a polyaniline complex (PANC). The polymer was synthesized by heating aniline in the presence of iodine and subsequent purification of the complex formed by Soxhlet extraction. Apart from PANC, an anilinohydrate, formed as a result of competing reactions, could be separated from the reaction mass and identified. Increase in iodine concentration (above the molar ratio aniline : iodine= 1 : 1.75) results in a decrease in yield of the PANC, whereas the yield of the anilinohydrate increases (Fig. 1). A control test showed that the anilinohydrate is not thermally polymerized up to 250°C, and consequently it is not an intermediate. In this process the iodine plays a multi-functional part. At the beginning of the process the aniline, and also many aromatic compounds [7] form a charge transfer complex with the iodine, with polarization of the C - H and N - H bonds; on heating the complex thus formed in an iodine medium the iodine acts as a catalyst for oxidative dehydropolycondensation. The HI released as a result of the reaction reacts with the polyaniline formed, and gives the polyhydrate form. * Vysokomol. soyed. A31: No. 9, 1950-1954, 1989. 2148
New highly conductive polymer complex based on aniline
2149
Increase in the synthesis temperature above 175°C results in a fall in the PANC yield (Fig. 2), whereas polymer degradation, according to T G A data, begins only at 250°C. The decrease in PANC yield is probably associated with rupture o[ the active complex between aniline and iodine.
Yleid %
Yield, % 70
3O
30
e'l"---
"
1 1
0.5
150
l.O Z2, moles
_
l
250
1
350 T°
Flo. 1 FIO. 2 FIG. I. Yield of PANC (1) and aniline iodohydrate (2) as a function of iodine concentration. T=175°C, z = 2 hr. FIG. 2. Yield of PANC as a function of temperature. Here and in Fig. 3 T=2 hr, molar ratio iodine : aniline=0.75 : 1. The iodine content of the polymer is almost independent of the synthesis temperature (Fig. 3) and is 52-60%, which corresponds to the composition (PANC)I.0Ios-1.1. On alkali treatment of PANC the iodine content in the polymer can be decreased to 32Yo, and formation of a fraction insoluble in D M F A is observed. The process is almost complete after 2 hr, and further heating of the reaction mass does not increase the yield (Fig. 4), and results in no significant structural changes.
Yield. % 60 -
_-re,%
qO qO
20 ]
200
I
300 T o
o/-
--
/ l
3
1
7 "-'h'. %,,
FIG. 3 FIG. 4 FIG. 3. Iodine content of PANC as a function of polymerization temperature. FIG. 4. Yield of PANC as a function of process time. T = 175°C, molar ratio iodine : aniliner0.75 : 1. C o m p a r i s o n o f the I R s p e c t r a o f P A N C with aniline b l a c k o b t a i n e d as d e s c r i b e d b y P a r i n i et al. [1] r e v e a l e d significant s t r u c t u r a l difference (Fig. 5). Skeletal p l a n a r v i b r a t i o n s o f the C = C b o n d o f the c o n j u g a t e d a r o m a t i c r i n g a r e o b s e r v e d in the 1R s p e c t r u m o f P A N C in the r e g i o n o f 1560 c m -a (1600 c m - 1 in aniline), a n d also very w e a k a b s o r p t i o n o f the u n c o n j u g a t e d a r o m a t i c ring in the r e g i o n o f 1500 c m -1. I n
A. M. ARZU~NYAN et aL
2150
~o
33
27
71
15
.9 v, am-I
FIO. 5. IR spectra of PANC (1) and aniline black (2). view of the low molecular mass (2000) the proportion of end groups is fairly high, amounting to 20 Yo, as result of which extra-planar deformational vibrations o f the C - H bond of the monosubstituted aromatic ring are observed in the IR spectrum in the region of 690 and 740 c m , 1. Growth of the polymer chain occurs mainly at positions 4 and 3-5 relative to the ring nitrogen atom. This is shown by the presence in the IR spectrum of characteristic deformational vibrations of the 1,4- and 1,3,5substituted aromatic rings in the region of 1090, 1160, and 1110 era-1.
II
o,7.
'
+NH3 '
In-
il
NH~ ' I
7~
-
III
The wide absorption (2800-3100 cm-1) with a maximum in the region of 2960 cm-1 is due to the NH~ group, and absorption characteristic of the NH + is observed in the region of 2588 cm-1 [8]. These data indicate the presence of the polyhydrate form in the polymer, and the presence of wide band absorption (3400-3650) with a maximum in the region of 3500 cm -1, which is characteristic of the NH bond of both primary and secondary amines, can indicate that not all the polymer chain units form the salt form. The absorpt!on band in the region of 1620 cm -1 is obviously associated with deformational vibrations of the NH bond of the iodohydrates, similar to the absorption obseIved with hydrochloride [8]. Structure III can be formed as a result of further oxidation under reaction conditions similar to those for aniline black [9]. To obtain a quantitative evaluation of the structural units I and II dimethylaniline was used as a model, the polymerization of which at positions 4 relative to the ring nitrogen atom is almost eliminated. As would be expected, the yield of polydimethyl,
New highly conductive polymer complex based on aniline
2151
aniline is very low, amounting to 6-8 ~o. Consequently (provided it is assumed that the polymerization of dimethylaniline occurs at positions 3 and 5) growth of the PANC chain occurs mainly at position 4 relative to the ring nitrogen atom. Allowing for the yields of PANC and polydimethylaniline, the proportion of polymer units of structure ] amounts to 10-12~o. On iodination, polycyclic aromatic compounds form small chain polyidoiodates [10], the nature of which has not yet been finally established, although Marks and Kalina [11] suggested that I7 ions are present. Investigation of the UV spectra of PANC showed tlaat in the region of 295 nm absorption occurs corresponding to the I~ anion [12], and the maxima in the region of 520, 550, 600, and 655 cm- 1 indicate the presence of long polyiodoiodate chains (Fig. 6) [13]. On decreasing the iodine content of the polymer 23 70
\ -- \
jf-~\
\\ \
I
ao
I
l
200
400
1
I
BOO 800 ,Tt717177
FIG. 6. UV spectra of PANC, containing 56 (1) and 32y0 iodine (2).
by alkali treatment the intensities of absorption of the polyiodoiodate forms are decreased, with a simultaneous increase in concentration of the I~ anions. Moreover, some hypsochromic shifts in the positions of the above maxima are observed (480, 550, 580 and 650), which also indicates a decrease in length of the polyiodoiodate chain on decreasing the iodine content of the polymer. The polymer PANC is a black powder, completely soluble in DMFA and partially (50 ~o) in chloroform. The specific electrical conductivity of specimen I, which contains 56~o iodine, is a2o=3.8 × 10 -3 ohrn-1/cm, and of specimen II, which contains 3 2 ~ iodine, a2o=7.3 x 10 -4 ohm-1/cm. The polymer is paramagnetic: the concentration of paramagnetic centres in specimen I is 2 x 1018 spin/g, width 0.9 roT, and of specimen II 8x10 is spin/g, width 0.9 mT. With increase in iodine concentration the intensity of the ESR signal falls, which is associated with disturbance of the conjugation by complex formation. The ESR spectrum of PANC consists of two narrow overlapping signals, which confirms the existence of the polymer in two forms, i.e. highly alloyed (conducting) and unalloyed (didectric). Similar phenomena have been observed by the present authors and by Matnishyan et aL [14] in the case of the polypyridine complex
2152
A.M.A.R-ARA.RA.RA.R~.s.NYANet al.
with iodine. The polymer P A N C is distinguished by its high stability in air: the iodine content is decreased by a mere 1-2 ~o over a year, and its specific electrical conductivity is almost unchanged over the same period. This polymer differs from known conducting p-type polymers in that the number o f electrons associated with the polymer chain is not changed during doping. Polymers with such a set of valuable properties can be used a s semiconductors. T h e polymerization method which we have considered also provides a means of obtaining a modified polymer of aniline black. On heating (150°C), in the presence of iodine, the aniline black fraction soluble in D M F A , the oligomer undergoes further polymerization, resulting in an increase in molecular weight, and the solubility in organic solvents is lost. The iodine content in the modified polymer is 5270, 0"20= 10 -4 o h m - I / c m . On alloying aniline black with gaseous H I the iodine content of the polymer is still higher than 6670, and a 2 0 = 2 x 10 - 4 o h m - I / s e e . As a result of electron donor interaction, strong phonon absorption, similar to aniline black, is observed in the I R ~pectra of the modified polymer and the polymer alloyed with HI, which hinders structural investigations o f these polymers. The IR spectra of the polymer specimen were obtained with a UR-20 spectrometer in thin films and in tablets with KBr, and the UV spectra were obtained with a "Speeord" spectrometer, chloroform as solvent, specimen concentration 10-3 mole/l. The ESR spectra were recorded with a "'E-3 Varian" instrument, using diphenylpicrylhydrazyl as standard. The dynamic TGA data were obtained with a Paulik-Paulik derivatograph, at a heating rate of 5 K/rain. The electrical conductivity of the polymer specimens, in the form of compacted tablets (pressure 150 x 105 PA) or films, was measured with a E6-13 terraohmeter. The molecular mass of the polymers was evaluated by a cryoseopic method in dioxane and by the Rast method in camphor. Pure, twice distilled aniline was used. The iodine was purified by sublimation. The aniline was polymerized in sealed, previously degassed ampouples (10 -2 mmHg) in an inert gas medium (argon or helium). In the ampoules was placed 0.93 g (0.01 mole) of aniline and from 0.63 g (0.0025 mole) to 3.8 g (0.015 mole) of iodine, and the ampoules were heated in a vertical furnace under dynamic conditions, i.e. 5 K/rain, until the required temperature was obtained (120300°C), and were then held at this temperature for 0.5 to 10 hr. The polymers were purified by Soxhlet ether extraction over 3-5 hr, and then by vacuum sublimation (1 mmHg) to constant weight, 10-407. (with respect to aniline) of the aniliniodohydrate being sublimated on the condenser, Tm,~--180"C (with decomposition). Found, 70:58"1 I, 6-1 N. Synthesis of aniliniodohydrate (for identification). A mixture of naphthalene or anthracene with iodine was heated to 140°C, the HI evolved on reaction was passed through a 25~/0solution of aniline in ether, and the residue of aniliniodohydrate deposited was washed with ether and dried, Tree= 180°C (with decomposition). Calculated, Yo: 57.03 I, 6.3 N. Found, ~o, 58.06 I, 6.8 N. The PANC was alkali treated with a concentrated KOH solution over 3-5 days at room temperature, and was then washed with distilled water and dried. The dimethylaniline was polymerized in sealed ampoules: 1.21 g (0"01 mole) of dimethylaniline and 1.26 g (0.005 mole) of iodine were heated at 1750C over 5 hr. The polymer was isolated by deposition from DMFA solution in water. The aniline black was heated in the presence of iodine in a sealed ampoule at 150°C over 2 hr. The aniline black was alloyed by passing gaseous HI through a layer of polymer over 2 hr. The polymers were purified by Soxhlet ether extraction and dried to constant weight under vacuum at 50°C. Translated by N. STANDEN
Modification of polyethylene surface sensitized with anthraquinone-9,10
2153
REFERENCES 1. V. P. PARINI, Z. S. KAZAKOVA and A. A. BERLIN, Vysokomol. soyed. 3: 1870, 1961 (Not translated in Polymer Sci. U.S.S.R.) 2. M. JOZEFOWICZ and G. BOLOGREJ, C. r. Acad. Sci. 260: 2037, 1965 3. J. LANGER, Solid State Commun. 26: 839, 1978 4. J. OHSAKA, Y. OHNUKI, M. OYAMA, G. KATAGIRU and K. KAMISAKO, S. Electroanal. Chem. 161: 399, 1984 5. A. A. MATNISHYAN, A. M. ARZUMANYAN, L. S. GRIGORYAN, I. L. ARUTYUNYAN, S. G. GR1GORYAN, R. S. ASATRYAN, A. L. MANUKYAN and R. O. MATEVOSYAN, Arm. khim. zh. 38: 590, 1985 6. A. A. MATNISHYAN, I. L. ARUTYUNYAN and A. M. ARZUMANYAN, Arm. khim. zh. 38: 728, 1985 7. B. TILGUIN and L. LAMBERTS, J. Phys. Chem. 84: 84, 1975 8. L. BELLAMY, Infakrasnye spektry slozhnykh molekul (Infrared Spectra of Complex Molecules). Moscow, 1963 9. A. G. MACDIARMID, J.-C. CHANG, W.-S. HUANG, A. F. RICHTER and A. I. EPSTEIN, Intern. Conf. on Science and Technology of Synthetic Metals Kyoto, 2, 1986 10. J. KOMMANDEUR and F. R. HALL, J. Chem. Phys. 34: 129, 1981 11. T. J. MARKS and D. W. KALINA, Extended Linear Chain Compounds 1: New York, 197, 1982 12. K. TOGODA and W. B. PERSON, J. Amer. Chem. Soc. 88: 1629, 1966 13. B. D. STEPIN and S. B. SPEPINA, Uspekhi khimii 55: 1434, 1986 14. A. A. MATNISHYAN, A. M. ARZUMANYAN and L. S. GRIGORYAN, Tez. Mezhdunar. konf. "Organicheskie materialy dlya elektroniki i priborostroeniya (Thesis of International Conference "Organic Materials for Electronics and Instrument Construction). Tashkent, 1987
Polymer Science U.~I.S.R. Vol. 31, No. 9, pp. 2153-2161, 1989 Printed in Poland
0032-3950189 $10.00+ .00 © 1990 Pergamon Pre~ pie
MODIFICATION OF A POLYETHYLENE SURFACE SENSITIZED WITH ANTHRAQUINONE-9,10 BY PHOTOOXIDATION. A KINETIC MODEL* A. A . DALINKEVICH, S. G . KIRYUSHKIN a n d Y u . A . SHLYAPNIKOV Institute of Chemical Physics, U.S.S.R. Academy of Sciences (Received 2 March 1988) A kinetic model for the photooxidative modification of PE in the presence of a sensitizer is proposed. The model takes into account the specific stages of polymer oxidation, degradation processes, taking place in the polymer, propagation of the oxidation chain along the macromolecule, and its transfer to an adjacent one. A decrease in the adhesional strength of the PE (strength of adhesional bonds) occurs as a result of degradation on repeated oxidation of * Vysokomol. soyed. A31: No. 9t 1955-1961, 1989.