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Synthesis of linear and crosslinked polymides based on diamines of the fluorene series
SYNTHESIS OF LINEAR AND CROSSLINKED POLYIMIDES BASED ON DIAMINES OF THE FLUORENE SERIES* O. YA. :FEDOTOVA,YE. I. ~TESTEROVA,V. V. KORSHAK and M. A. IL'YEI~KO D. I. MendeleyevChemicalTechnologyInstitute, Moscow (Received 28 June 1971)
OWE of the possible methods of obtaining heat and temperature resistance as well as other useful properties in polymers is known to be to change from linear to three-dimensional structures. The present work is therefore devoted to the synthesis of polyimides with free functional groups capable of further chemical transformations with the formation of intermolecular bonds. The reaction between active methylene groups and carbonyl compounds, known as the aldol condensation [1], was used for the erosslinking of the polymer. The following were used as the starting compounds: 2,7-diaminofluorene (2,7-DAF), 2,7-diaminofluorenone (2,7-DAFO), 4,4'-diaminodiphenylmethane (DDM) and the dianhydride of benzophenonetetraearboxylic acid (DATC), all of which contain active methylene and ketone groups. The crosslinking of the polymers was carried out by vacuum heat treatment. In order to compare the properties of crosslinked polymers with those of the corresponding linear polymers, the polypyromellitimides based on 2,7-diaminofluorene and 2,7-diaminofluorenone were synthesized. The synthesis of the polymers was carried out by a two-stage method, the first stage being performed in amide-type solvents. DISCUSSION OF RESULTS
In connection with the fact that 2,7-DAF and 2,7-DAFO had not been used previously for the synthesis of polyamido-acids (PAA), the conditions for the synthesis of these polymers were studied in detail and the effect of the following on the molecular weight and polymer yield were investigated; certain nucleophilie solvents, the temperature and duration of the reaotion and the concentrations of the starting substances. The change in molecular weight as a function of the reaction conditions was followed from the change in the reduced viscosity of 0.5% polymer solutions in dimethylsulphoxide. The data obtained are shown in Fig. 1. The relationships fotmd are similar to the corresponding ones obtained for the acylation of the same diamines by isophthaloyl chloride [2]. * Vysokomol. soyed. A15: No. 7, 1502-1505, 1973.
1683
1684
O. YA. FEDOTOVA et al.
The PAA based on 2,7-DAFO are red powders, whereas the PAA based on 2,7-DAF are greenish whatever acid component is used. All the polyamido-acids synthesized were soluble in N-pyrrolidone (N-MP), dimethylacetamide (DMAA),
a
as
c
b
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~,,
3 /}#
0.z t
1
-qO
I
I
O
L
L
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•
0.0
o2
=3'
~~'
I
q
Time,# hr 8
2
I
I
i~2
1
I
C,rno'-~'0"#/¢'1,.
FIG. 1. D e p e n d e n c e of t h e reduced viscosities of 0.5yo solutions of P A A on: a - - t e m p e r a t u r e a n d b - - d u r a t i o n of synthesis, a n d c - - o n t h e c o n c e n t r a t i o n of t h e s t a r t i n g components, for P A A based on: 1 - - P M D A a n d ,2,7-DAF; 2 - - D A T C a n d 2,7-DAF; 3 - - P M D A a n d 2,7-DAFO; a: c = 0 . 1 mole/1, 2 hr, solvent D M A A ; b: c = 0 . 1 mole/1, 20°C; 3 ' - - D M S O as solvent; 3 " - N - M P as solvent; c: 20°C, 2 hr, D M A A as solvent.
dimethylsulphoxide (DMSO), dimethylformamide (DMFA) and were insoluble in the ordinary organic solvents. The structure of the PAA was confirmed by chemical analysis and IR spectra.
o
-L]
7G
°zo
o~ lO
Go ,oo T/rne , m/'n FIG. 2
,8o 70tl FIO. 3
Fro. 2. Kinetic curves for the v~ight loss of the PAA based on PMDA and 2,7-DAFO at the following temperatures: I--140; 2--220; 3--240; d--280; 5--300; 6--320°C. FIG. 3. TGA curves for the heating in air of the followingpolyimides based on: 1--PMDA and 2,7-DAF; 2--DATC and 2,7-DAF; 3--PMDA and 2,7-DAFO; 4--PMDA and an equimolar m i x t u r e of 2,7-DAFO a n d D D M .
Synthesis of polyimides
1685
T h e i m i d i z a t i o n conditions for the P A A o b t a i n e d c o n v e r t e d t h e m i n t o linear p o l y p y r o m e l l i t i m i d e s i n c a p a b l e o f f o r m i n g i n t e r m o l e c u l a r crosslinks. Cyclodehyd r a t i o n was carried o u t in v a c u u m a t v a r i o u s t e m p e r a t u r e s ; t h e conversion o f P A A i n t o t h e p o l y i m i d e was e s t i m a t e d f r o m t h e w e i g h t losses d e t e r m i n e d u n d e r i s o t h e r m a l conditions on a M a c B a i n b a l a n c e a n d f r o m t h e I R - s p e c t r a d a t a . I t m a y be seen f r o m Fig. 2 t h a t t h e weight losses are v e r y m u c h in excess of t h e calculated a m o u n t o f w a t e r e v o l v e d during c y c l o d e h y d r a t i o n (6%). I R spectrosc o p y s h o w e d t h a t i m i d i z a t i o n is a l r e a d y c o m p l e t e a t 240°C (see Table), w h e r e a s D E P E N D E N C E OF T H E O P T I C A L D E N S I T Y OF T H E C H A R A C T E R I S T I C B A N D S * ON T H E H E A T - T R E A T lYIENT T E M P E R A T U R E OF
T, °C
1544) I
PAA
Optical density absorption bands, cm -1 1380[ 1728[ 1780 1430 1665
990
2.7-DAF+DATC Initial PAA 140 220 260 280 300
0"21 0"15 0'05
0'08 0"20 0"27 0"29 0"29 0'29
0.3 0-36 0"38 0.41 0.41 0.41
0'01 0"02 0"03 0"03 0"03 0'03
0"18 0"18 0"14 0"10 0"05
0"21 0"21 0"18 0"14 0"08
0-2 0"3 0"29
2"7-PAF + PMDA Initial PAA 140 220 260 280 300
0"04 0"04 0"02
0"1 0"22 0"23 0'23
0'06 0"11 0'17 0"37 0"37 0"4
0-01 0"01 0"04 0"05 0"05 0"05
0"14 0'14 0'14 0"14 0"14 0-14
2.7-DAFO + DDM + PMDA Initial PAA 140 220 260 280 300
0"10 O'08
0'07 0"10 0"16 0"18 0"18 0'18
--
0'16 0'18 0"22 0"22 0"22
0"10 0"05 0'08 0"08 0"08 0"08
0'10 0"10 0"07 0"05 0"03 0"03
0'l 0"1 0'16 0"18
* 1 5 4 0 c m - ~ , - - N H C O - - ; 1430 c m - ~ , - - A r - - C H a - - A r ; 1665 c m - l , - - A r - - O - - A r ; 990era -~, double bond; 1380 1728 and 1780 cm -~, imide ring. [I O
t h e e v o l u t i o n of volatiles continues u p to 320°C. Since the yield of the s y n t h e s i z e d P A A , a f t e r being dried to c o n s t a n t w e i g h t a t 80°C in v a c u u m , is 1 2 - 2 5 % g r e a t e r t h a n t h a t t h e o r e t i c a l l y possible, t h e weight losses a b o v e 240°C can be exclusively a t t r i b u t e d to t h e e v o l u t i o n of t h e solvent. I n fact, in t h e case of t h e p o l y m e r b a s e d on 2 , 7 - D A F O t r e a t e d b e f o r e h a n d in v a c u u m a t 240°C, the weight losses a t 320°C were 8%, a n d t h e condensed volatile p r o d u c t was identified f r o m its boiling p o i n t
1686
O. YA. FEDOTOVAet al.
a n d refractive coefficient as DMMA. The final h e a t t r e a t m e n t of P A A was therefore carried o u t for 2 hr a t 300°C. The f o r m a t i o n of crosslinks t h r o u g h the reaction b e t w e e n the m e t h y l e n e g r o u p of the fluorene ring a n d the carbonyl g r o u p was studied in p o l y m e r s in which a k e t o n e g r o u p was i n t r o d u c e d either with the acid c o m p o n e n t (DATC) or with the a m i n e c o m p o n e n t (equimolar m i x t u r e of 2,7-DAFO a n d DDM) into the m a k e u p of the e l e m e n t a r y unit. I R s p e c t r o s c o p y showed t h a t , in parallel with the imidization of the p o l y a m i d o acids, an intermolecular interaction t a k e s place b e t w e e n the functional groups a n d this is a c c o m p a n i e d b y the g r a d u a l disappearance of the a b s o r p t i o n b a n d s in the region of 1430 a n d 1665 cm -1 t h a t are a t t r i b u t a b l e to ~ C H 2 a n d ~ C = O groups respectively (see Table). These b a n d s are f o u n d to disappear completely a t 300°C. No change is observed in the int e n s i t y o f the a p p r o p r i a t e a b s o r p t i o n b a n d s in the case of polyimides t h a t do n o t contain c a r b o n y l and m e t h y l e n e groups simultaneously. The f o r m a t i o n of a ~C-----C~ b o n d in the p o l y m e r was recorded in the I R spectra f r o m the a p p e a r a n c e of a new a b s o r p t i o n b a n d in the region of 990 cm -1 t h a t relates to v a l e n c y vibrations of this b o n d [3]. T h e r m o g r a v i m e t r i c analysis of the linear a n d crosslinked polymers synthesized indicates a n increase in resistance to t h e r m a l oxidation in the case of the crosslinked polyimides as c o m p a r e d with the corresponding linear analogues (Fig. 3).
EXPERIMENTAL Starting substances. Pyromellitic dianhydride was purified by vacuum distillation and used with a boiling point of 285-286°C. The dianhydride of 3,3', 4,4'-benzophenonetetracarboxylic acid was purified by recrystallization from acetic hydride, melting point 226-227°C (literature data, 226°C). 2,7-Diaminofluorene and 2,7-diaminofluorenone were synthesized by the method given in [4] and were used with the respective melting points: 158°C (157°C according to [4]) and 286°C {284-285°C according to [5]). Dimethylacetamide was dried with P~O~, then distilled, and the fraction with a boiling point of 167°C was taken (literature data, 167°C). Dimethylsulphoxide was dried with Call2, then distilled under vacuum and the fraction with a boiling point of 92-93°C/1 mmHg was selected. N-methyl-2-pyrrolidone was distilled over CaH~ and the fraction with a boiling point of 90°C/4 mmHg was selected. The synthesis of the polyamido acids was carried out in a three-necked flask equipped with a stirrer, calcium chloride tube and a capillary for the introduction of nitrogen. An equimolar quantity of the solid dianhydride was added in small portions to a solution of the diamino held thermostatically at the given temperature whilst being stirred. After the introduction of the dianhydride, the stirring was continued at the given temperature for 0-5 hr after which the thermostatic treatment ceased and the stirring was continued at room temperature for another 2 hr. At the end of the reaction the polyamido acid was precipitated, washed with water and acetone and dried at 80°C in vacuum to constant weight. The reduced viscosity of 0"5yo solutions of the polymers was determined in DMSO at 25°C. The structure of the polymers was studied with a IK-10 spectrophotometer, the polymer being formed into a tablet with KBr. The weight losses were studied with a MacBain balance. The thermogravimetric investigations were made with a derivatograph at a rate of tempera~ t u ~ rise of 3°C/min in air.
Thermal degradation of poly-l,3,4-oxadiazoles
1687
CONCLUSIONS
(l) High-molecular polyamido acids and polyimides based on 2,7-diaminofluorene and 2,7-diaminofluorenone have been synthesized and certain rules of their formation have been studied. (2) It has been shown to be possible to form intermolecular bonds through a reaction between the active methylene group of diaminodiphenyl methane and earbonyl groups and it has been shown that the crosslinked polyimides haw~ a higher thermo-oxidative resistance than that of the corresponding linear polymers. Translated by G. F. MODLE~ REFERENCES 1. R. C. FUSON, Reatsii organicheskikh soyedinenii (Reactions of Organic Compounds). p. 431, "Mir", 1966, (Russian translation) 2. O. Ya. FEDOTOVA, V. V. KORSIL~kK and Ye. I. NESTEROVA, Vysokomol. soyed. A15: 80, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 1, 1973) 3. L. BELLAMY, Infrakrasnye spektry slozhnykh molekul (Infrared Spectra of Complex Molecules). Izd. inostr, lit., 1963 (Russian translation) 4. G. T. lYIORGF_~and R. W. TItOMASON, J. Chem. Soc., 2691, 1926 5. A. BARKER and C. C. BARKER, J. Chem. Soc., 870, 1954
THERMAL DEGRADATION OF POLY-1,3,4-0XADIAZOLES CONTAINING CARBORANE NUCLEI IN THE MAIN CHAIN* t). N. GRIBKOVA, T. N. BALYKOVA, L. A. GLIVKA, P. M. VALETSKII, S. V. VINOGRADOVAa n d V. V. KORSHAK Institute for Elemento-Organic Compounds, U.S.S.R. Academy of Sciences
(Received 22 July 1971)
THE present paper is devoted to a study of the thermal degradation of poly-l,3,4oxadiazoles containing 1,2- and 1,7-diphenylcarborane fragments in the main chain. For this purpose, the following were selected: polyoxadiazoles based on 1,7-bis(4-earboxyphenyl)earborane (polymer I) and 1,2-bis-(4-earboxyphenyl)earborane (polymer II), as well as 1,2-bis-[4-(5-phenyl-l,3,4-oxadiazole) phenyl] carborane (M-l), a compound acting as a model for the elementary unit in polymer II. In order to clarify the special features of the thermal properties of polyox~liazoles * Vysokomol. soyed. AI5: No. 7, 1506-1512, 1973.
OWE of the possible methods of obtaining heat and temperature resistance as well as other useful properties in polymers is known to be to change from linear to three-dimensional structures. The present work is therefore devoted to the synthesis of polyimides with free functional groups capable of further chemical transformations with the formation of intermolecular bonds. The reaction between active methylene groups and carbonyl compounds, known as the aldol condensation [1], was used for the erosslinking of the polymer. The following were used as the starting compounds: 2,7-diaminofluorene (2,7-DAF), 2,7-diaminofluorenone (2,7-DAFO), 4,4'-diaminodiphenylmethane (DDM) and the dianhydride of benzophenonetetraearboxylic acid (DATC), all of which contain active methylene and ketone groups. The crosslinking of the polymers was carried out by vacuum heat treatment. In order to compare the properties of crosslinked polymers with those of the corresponding linear polymers, the polypyromellitimides based on 2,7-diaminofluorene and 2,7-diaminofluorenone were synthesized. The synthesis of the polymers was carried out by a two-stage method, the first stage being performed in amide-type solvents. DISCUSSION OF RESULTS
In connection with the fact that 2,7-DAF and 2,7-DAFO had not been used previously for the synthesis of polyamido-acids (PAA), the conditions for the synthesis of these polymers were studied in detail and the effect of the following on the molecular weight and polymer yield were investigated; certain nucleophilie solvents, the temperature and duration of the reaotion and the concentrations of the starting substances. The change in molecular weight as a function of the reaction conditions was followed from the change in the reduced viscosity of 0.5% polymer solutions in dimethylsulphoxide. The data obtained are shown in Fig. 1. The relationships fotmd are similar to the corresponding ones obtained for the acylation of the same diamines by isophthaloyl chloride [2]. * Vysokomol. soyed. A15: No. 7, 1502-1505, 1973.
1683
1684
O. YA. FEDOTOVA et al.
The PAA based on 2,7-DAFO are red powders, whereas the PAA based on 2,7-DAF are greenish whatever acid component is used. All the polyamido-acids synthesized were soluble in N-pyrrolidone (N-MP), dimethylacetamide (DMAA),
a
as
c
b
!
~,,
3 /}#
0.z t
1
-qO
I
I
O
L
L
#OT,°C 80
•
0.0
o2
=3'
~~'
I
q
Time,# hr 8
2
I
I
i~2
1
I
C,rno'-~'0"#/¢'1,.
FIG. 1. D e p e n d e n c e of t h e reduced viscosities of 0.5yo solutions of P A A on: a - - t e m p e r a t u r e a n d b - - d u r a t i o n of synthesis, a n d c - - o n t h e c o n c e n t r a t i o n of t h e s t a r t i n g components, for P A A based on: 1 - - P M D A a n d ,2,7-DAF; 2 - - D A T C a n d 2,7-DAF; 3 - - P M D A a n d 2,7-DAFO; a: c = 0 . 1 mole/1, 2 hr, solvent D M A A ; b: c = 0 . 1 mole/1, 20°C; 3 ' - - D M S O as solvent; 3 " - N - M P as solvent; c: 20°C, 2 hr, D M A A as solvent.
dimethylsulphoxide (DMSO), dimethylformamide (DMFA) and were insoluble in the ordinary organic solvents. The structure of the PAA was confirmed by chemical analysis and IR spectra.
o
-L]
7G
°zo
o~ lO
Go ,oo T/rne , m/'n FIG. 2
,8o 70tl FIO. 3
Fro. 2. Kinetic curves for the v~ight loss of the PAA based on PMDA and 2,7-DAFO at the following temperatures: I--140; 2--220; 3--240; d--280; 5--300; 6--320°C. FIG. 3. TGA curves for the heating in air of the followingpolyimides based on: 1--PMDA and 2,7-DAF; 2--DATC and 2,7-DAF; 3--PMDA and 2,7-DAFO; 4--PMDA and an equimolar m i x t u r e of 2,7-DAFO a n d D D M .
Synthesis of polyimides
1685
T h e i m i d i z a t i o n conditions for the P A A o b t a i n e d c o n v e r t e d t h e m i n t o linear p o l y p y r o m e l l i t i m i d e s i n c a p a b l e o f f o r m i n g i n t e r m o l e c u l a r crosslinks. Cyclodehyd r a t i o n was carried o u t in v a c u u m a t v a r i o u s t e m p e r a t u r e s ; t h e conversion o f P A A i n t o t h e p o l y i m i d e was e s t i m a t e d f r o m t h e w e i g h t losses d e t e r m i n e d u n d e r i s o t h e r m a l conditions on a M a c B a i n b a l a n c e a n d f r o m t h e I R - s p e c t r a d a t a . I t m a y be seen f r o m Fig. 2 t h a t t h e weight losses are v e r y m u c h in excess of t h e calculated a m o u n t o f w a t e r e v o l v e d during c y c l o d e h y d r a t i o n (6%). I R spectrosc o p y s h o w e d t h a t i m i d i z a t i o n is a l r e a d y c o m p l e t e a t 240°C (see Table), w h e r e a s D E P E N D E N C E OF T H E O P T I C A L D E N S I T Y OF T H E C H A R A C T E R I S T I C B A N D S * ON T H E H E A T - T R E A T lYIENT T E M P E R A T U R E OF
T, °C
1544) I
PAA
Optical density absorption bands, cm -1 1380[ 1728[ 1780 1430 1665
990
2.7-DAF+DATC Initial PAA 140 220 260 280 300
0"21 0"15 0'05
0'08 0"20 0"27 0"29 0"29 0'29
0.3 0-36 0"38 0.41 0.41 0.41
0'01 0"02 0"03 0"03 0"03 0'03
0"18 0"18 0"14 0"10 0"05
0"21 0"21 0"18 0"14 0"08
0-2 0"3 0"29
2"7-PAF + PMDA Initial PAA 140 220 260 280 300
0"04 0"04 0"02
0"1 0"22 0"23 0'23
0'06 0"11 0'17 0"37 0"37 0"4
0-01 0"01 0"04 0"05 0"05 0"05
0"14 0'14 0'14 0"14 0"14 0-14
2.7-DAFO + DDM + PMDA Initial PAA 140 220 260 280 300
0"10 O'08
0'07 0"10 0"16 0"18 0"18 0'18
--
0'16 0'18 0"22 0"22 0"22
0"10 0"05 0'08 0"08 0"08 0"08
0'10 0"10 0"07 0"05 0"03 0"03
0'l 0"1 0'16 0"18
* 1 5 4 0 c m - ~ , - - N H C O - - ; 1430 c m - ~ , - - A r - - C H a - - A r ; 1665 c m - l , - - A r - - O - - A r ; 990era -~, double bond; 1380 1728 and 1780 cm -~, imide ring. [I O
t h e e v o l u t i o n of volatiles continues u p to 320°C. Since the yield of the s y n t h e s i z e d P A A , a f t e r being dried to c o n s t a n t w e i g h t a t 80°C in v a c u u m , is 1 2 - 2 5 % g r e a t e r t h a n t h a t t h e o r e t i c a l l y possible, t h e weight losses a b o v e 240°C can be exclusively a t t r i b u t e d to t h e e v o l u t i o n of t h e solvent. I n fact, in t h e case of t h e p o l y m e r b a s e d on 2 , 7 - D A F O t r e a t e d b e f o r e h a n d in v a c u u m a t 240°C, the weight losses a t 320°C were 8%, a n d t h e condensed volatile p r o d u c t was identified f r o m its boiling p o i n t
1686
O. YA. FEDOTOVAet al.
a n d refractive coefficient as DMMA. The final h e a t t r e a t m e n t of P A A was therefore carried o u t for 2 hr a t 300°C. The f o r m a t i o n of crosslinks t h r o u g h the reaction b e t w e e n the m e t h y l e n e g r o u p of the fluorene ring a n d the carbonyl g r o u p was studied in p o l y m e r s in which a k e t o n e g r o u p was i n t r o d u c e d either with the acid c o m p o n e n t (DATC) or with the a m i n e c o m p o n e n t (equimolar m i x t u r e of 2,7-DAFO a n d DDM) into the m a k e u p of the e l e m e n t a r y unit. I R s p e c t r o s c o p y showed t h a t , in parallel with the imidization of the p o l y a m i d o acids, an intermolecular interaction t a k e s place b e t w e e n the functional groups a n d this is a c c o m p a n i e d b y the g r a d u a l disappearance of the a b s o r p t i o n b a n d s in the region of 1430 a n d 1665 cm -1 t h a t are a t t r i b u t a b l e to ~ C H 2 a n d ~ C = O groups respectively (see Table). These b a n d s are f o u n d to disappear completely a t 300°C. No change is observed in the int e n s i t y o f the a p p r o p r i a t e a b s o r p t i o n b a n d s in the case of polyimides t h a t do n o t contain c a r b o n y l and m e t h y l e n e groups simultaneously. The f o r m a t i o n of a ~C-----C~ b o n d in the p o l y m e r was recorded in the I R spectra f r o m the a p p e a r a n c e of a new a b s o r p t i o n b a n d in the region of 990 cm -1 t h a t relates to v a l e n c y vibrations of this b o n d [3]. T h e r m o g r a v i m e t r i c analysis of the linear a n d crosslinked polymers synthesized indicates a n increase in resistance to t h e r m a l oxidation in the case of the crosslinked polyimides as c o m p a r e d with the corresponding linear analogues (Fig. 3).
EXPERIMENTAL Starting substances. Pyromellitic dianhydride was purified by vacuum distillation and used with a boiling point of 285-286°C. The dianhydride of 3,3', 4,4'-benzophenonetetracarboxylic acid was purified by recrystallization from acetic hydride, melting point 226-227°C (literature data, 226°C). 2,7-Diaminofluorene and 2,7-diaminofluorenone were synthesized by the method given in [4] and were used with the respective melting points: 158°C (157°C according to [4]) and 286°C {284-285°C according to [5]). Dimethylacetamide was dried with P~O~, then distilled, and the fraction with a boiling point of 167°C was taken (literature data, 167°C). Dimethylsulphoxide was dried with Call2, then distilled under vacuum and the fraction with a boiling point of 92-93°C/1 mmHg was selected. N-methyl-2-pyrrolidone was distilled over CaH~ and the fraction with a boiling point of 90°C/4 mmHg was selected. The synthesis of the polyamido acids was carried out in a three-necked flask equipped with a stirrer, calcium chloride tube and a capillary for the introduction of nitrogen. An equimolar quantity of the solid dianhydride was added in small portions to a solution of the diamino held thermostatically at the given temperature whilst being stirred. After the introduction of the dianhydride, the stirring was continued at the given temperature for 0-5 hr after which the thermostatic treatment ceased and the stirring was continued at room temperature for another 2 hr. At the end of the reaction the polyamido acid was precipitated, washed with water and acetone and dried at 80°C in vacuum to constant weight. The reduced viscosity of 0"5yo solutions of the polymers was determined in DMSO at 25°C. The structure of the polymers was studied with a IK-10 spectrophotometer, the polymer being formed into a tablet with KBr. The weight losses were studied with a MacBain balance. The thermogravimetric investigations were made with a derivatograph at a rate of tempera~ t u ~ rise of 3°C/min in air.
Thermal degradation of poly-l,3,4-oxadiazoles
1687
CONCLUSIONS
(l) High-molecular polyamido acids and polyimides based on 2,7-diaminofluorene and 2,7-diaminofluorenone have been synthesized and certain rules of their formation have been studied. (2) It has been shown to be possible to form intermolecular bonds through a reaction between the active methylene group of diaminodiphenyl methane and earbonyl groups and it has been shown that the crosslinked polyimides haw~ a higher thermo-oxidative resistance than that of the corresponding linear polymers. Translated by G. F. MODLE~ REFERENCES 1. R. C. FUSON, Reatsii organicheskikh soyedinenii (Reactions of Organic Compounds). p. 431, "Mir", 1966, (Russian translation) 2. O. Ya. FEDOTOVA, V. V. KORSIL~kK and Ye. I. NESTEROVA, Vysokomol. soyed. A15: 80, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 1, 1973) 3. L. BELLAMY, Infrakrasnye spektry slozhnykh molekul (Infrared Spectra of Complex Molecules). Izd. inostr, lit., 1963 (Russian translation) 4. G. T. lYIORGF_~and R. W. TItOMASON, J. Chem. Soc., 2691, 1926 5. A. BARKER and C. C. BARKER, J. Chem. Soc., 870, 1954
THERMAL DEGRADATION OF POLY-1,3,4-0XADIAZOLES CONTAINING CARBORANE NUCLEI IN THE MAIN CHAIN* t). N. GRIBKOVA, T. N. BALYKOVA, L. A. GLIVKA, P. M. VALETSKII, S. V. VINOGRADOVAa n d V. V. KORSHAK Institute for Elemento-Organic Compounds, U.S.S.R. Academy of Sciences
(Received 22 July 1971)
THE present paper is devoted to a study of the thermal degradation of poly-l,3,4oxadiazoles containing 1,2- and 1,7-diphenylcarborane fragments in the main chain. For this purpose, the following were selected: polyoxadiazoles based on 1,7-bis(4-earboxyphenyl)earborane (polymer I) and 1,2-bis-(4-earboxyphenyl)earborane (polymer II), as well as 1,2-bis-[4-(5-phenyl-l,3,4-oxadiazole) phenyl] carborane (M-l), a compound acting as a model for the elementary unit in polymer II. In order to clarify the special features of the thermal properties of polyox~liazoles * Vysokomol. soyed. AI5: No. 7, 1506-1512, 1973.