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Molecular weight characteristics of a cardic polyamidoester prepared by low temperature polycondensation
MOLECULAR WEIGHT CHARACTERISTICS OF A CARDIC POLYAMIDOESTER P R E P A R E D BY LOW TEMPERATURE POLYCONDENSATION* YE. D. MOLODTSOVA,S. A. PAVLOVA, G. I. TIMOFEYEVA, YA. S. VYGODSKII, S. V. VI:NOGRADOVA a n d V. V. KORSHAK I n s t i t u t e of Hetero-Organic Compounds, U.S.S.R. Academy of Sciences
(Received 55 January 1973)
A study has been made of the molecular weight characteristics of a stable polyamidoester of high molecular weight, prepared b y low temperature polycondensation of 2,5-dicarboxymethoxyterephthalyl chloride with 3,3-bis-(4-aminophenyl) phthalide. The hydrodynamic properties of this polyamidoester were investigated and the length of the K u h n statistical segment of the polymer chain has been calculated. I t was found t h a t this polyamidoester, obtained b y low temperature polycondensation, has a molecular weight distribution narrower t h a n the most probable distribution.
THE TWO stage polyeondensation method is used extensively for preparation of polyheteroarylenes of different structure. I n the preparation polymides by the two stage method of polycondensation soluble polyamidoacids (PAA) are obtained in the first stage. I n the second stage, the stage of intramolecular cyclization, the production of polyimides of high molecular weight in a purely thermal process is made difficult by the occurrence of considerable hydrolysis of the PAA by the water evolved. I n order to eliminate the catalytic effect of carboxyl groups and to increase the stability of the amide linkage of these polymers, a method has been proposed for preparation of polyimides through polyamidoesters (PAE), as stable derivatives of PAA's, obtained by low temperature polycondensatiorl of diacid chloride of diesters of tetracarboxylic acids with primary aromatic diamines, in solution in an amide solvent [1-3]. The greater resistance to hydrolysis of PAE's, in comparison with PAA's, erlabtes polyimides of high molecular weight to be obtained from them [3] and they also provide the possibility of carrying out a thorough investigation of their molecular weight characteristics, a knowledge of which would assist in understanding the laws of low temperature polycondensation in amide solvents. At the s£me time there are grounds for supposing that the molecular weight characteristics of the original PAE are of decisive importance in determining the properties of the polyimide. There is no information in the literature on the molecular weight characteristics of P A E ' s and the molecular weight characteristics of PAA's, studied in detail in references [4] and [5], can scarcely be regarded as being sufficiently accurate in view of th instability of PAA's.
* Vysokomol. soyed. AI6: No. 10, 2183-2189, 1974. 2529
2530
YE. D. I~OLODTSOVAet
al.
The purpose of the present work was to investigate the molecular weight characteristics of a cardic polyamidoester of the structure -
_oc_,~\_coocm
~
-I
o
_L,
:,
prepared by low temperature polycondensation in DMAA. EXPERIMENTAL The P A E was prepared b y low temperature polycondensation of 2,5-dicarbomethyloxyterephthalyl chloride with 3,3-bis-(4-aminophenyl)phthalide in exactly e q u i ~ o l a r quantities in D~IAA, by the m e t h o d of reference [3]. The reaction was carried out for 30 min at 10 ° and 2 hr at room temperature. A t the end of the reaction the polymer was isolated by pouring a diluted solution into water. I t was filtered off. washed several times with water, then acetone, and dried in vacuo at room temperature. The yield of polymer was quantitative. The stability of the P A E was tested at room temperature in suitable solvents. On storage of a 0.4% solution of the P A E in D M F t/tea had not changed after 11 days. W h e n a 0.5%
70'yM~pp
2,0-
1"0
7"5/
b 1"0 ~
3
0"8
q
0.5
/
2/2/j¢,/E /All~ //.IB
i/ / .,/.,ZZ
.1;'..'2/' 0"2 t
J
O'E 1"0 c~g/d! t
t
t
O;Z
1 O-Z
I
I
0.6
I
L_
!-:
c, ~q/a/
FIo. I. Concentration dependence of the molecular weight (a) and sedimentation constant (b) of the P A E ' s and some of their fractions. Continuous l i n e s - - P A E - 1 , broken l i n e s - - P A E - 2. The figures on the curves are the fraction numbers, 0 represents the unfractionated P A E .
Molecular weight characteristics of a cardic polyamidoester
2531
solution of a fraction of the P A E in N-methyl-2-pyrrolidone (MP) was kept for 7 days qred was unchanged. W h e n a 1% solution of the P A E in a phenol-TCE mixture was stored t/tea (originally 2.05) was 2.02 after 32 days and 2.01 after 67 days. Consequently the P A E is stable in these solvents. Two samples of the P A E (PAE-1 and PAE-2) were used for the investigation. They were prepared under the same conditions a n d h a d the following characteristics: P A E - h [~/]DMF = 0 ' 6 4 dl/g, [~1~P=0"77 dl/g, 2Qw----55,000; PAE-2:[r/]D•F=0"53 dl/g, [~/]Mp=0"74 dl/g, /t),o = 48,000. The p o l y m e r samples were fractionated from a 1% solution b y distribution between two liquid phases in the T C E - p h e n o l - h e p t a n e system. To obtain more reliable results two parallel fractions were carried out. Five grammes of each polymer were fractionated into t w e n t y four and t w e n t y three fractions of PAE-1 and PAE-2 respectively. The weight of the fractions was about 0.2 g. PAE-1 was first separated into several large fractions, each of which was then refractionated. I n the ease of PAE-2 each fraction was obtained successively in the course of the main fractionation. The viscosity of the original polymer and of all the fractions was measured in D M F a n d MP a t 25±0.05% at four concentrations in the 0.4-1.0 g/dl range in a suspended-level viscometer. The flow time of the solvent was 100-130 sec. The intrinsic viscosity [t/] was found by double graphical extrapolation of the curves of the Huggins equation to infinite dilution [6]. Sedimentation analyses were obtained in MOM (Hungary) 3170 a n d G-120 analytical ultracentrifuges, at a rotor t e m p e r a t u r e of 25q-0.1 °. The solvent for sedimentation analysis was DMF. " A p p a r e n t " molecular weights, M~pp were determined at four concentrations in the range of 0.2-0.7 g/dl, b y the unstable equilibrium method [7, 8]. The rotor speed was chosen so t h a t the gradient curve intersected the meniscus at a sufficiently large angle. The true molecular weight /ff/w was found b y graphical extrapolation of 1 / M ~ pp to infinite dilution (Fig. 1 (a). The specific p a r t i a l volume v of the polymer in DMF, measured in a pyknometer, was 0-704 cma/g, the density of D M F p = 0.947 g/era a. The sedimentation coefficient Sc of the original P A E and of the fractions was measured a t a rotor speed of ~ 50,000 rev/min at four concentrations in the range of 0-2-0-7 dl/g. The sedimentation constant SD were obtained b y graphical extrapolation to infinite dilution (Fig. 1 b). The results of fractionation and the molecular weight characteristics of the fractions are presented in Table 1. RESULTS AND DISCUSSION
I t is s e e n f r o m T a b l e 1 t h a t [~/] o f t h e P A E f r a c t i o n s i n D M F v a r i e s b e t w e e n 0.18 a n d 1.23 d l / g , a n d t h e m o l e c u l a r w e i g h t s f r o m 7800 t o 125,000. F r o m t h i s it may be concluded that fractionation of the polymers occurred with good selectivity. The log-log graphs of the relationship between the intrinsic viscosibies and m o l e c u l a r w e i g h t s o f t h e P A E f r a c t i o n s i n D M F a n d M P ( F i g . 2) h a v e t w o sections with different slopes and are described by the following equations: in the 1 2 5 , 0 0 0 - 2 8 , 0 0 0 m o l e c u l a r w e i g h t r e g i o n [~/]DMF----0"65× 1 0 - 4 × ~ S 4 ( I a ) a n d [r/]Me~--0-38 × 1 0 - 4 x 2tTr°'9° ( I b ) , a n d in t h e 2 8 , 0 0 0 - 8 0 0 0 m o l e c u l a r w e i g h t r e g i o n [r/]DMF=22"22 × 1 0 - 4 × /l~f°w"5° ( I I a ) a n d [~/]Mp= 16.62 × 1 0 - 4 x / Q ~ a ( I I b ) . The relationship between the sedimentation constants and molecular weights o f t h e P A E f r a c t i o n s i n t h e m o l e c u l a r w e i g h t r e g i o n o f 1 2 5 , 0 0 0 - 2 8 , 0 0 0 (Fig. 3a) is e x p r e s s e d b y t h e e q u a t i o n S D = 2 " 5 4 x 10 ~5 ×/t~Ow.a3.
2532
Y~. D. MOLODTSOVAet al. TABLE 1. ~AOTIONATION OF THE POLYAMIDO:ESTERSAMPLES*
Fraction No.
Total weight-fraction of thefractions ZW~+½W~+I
0.0077 0.0348 0-0752 0-1206 0-1691 0.2176 0.2637 7 0.3086 8 0.3429 9 0.3909 10 11 0.4452 12 0.4913 0.5473 13 0.6040 14 0.6581 15 16 0.7081 0.7528 17 0.7944 18 19 0"8314 0.8554 20 0.8803 21 22 0-9132 0.9459 23 0-9806 24 Orginal weight -- 5"0 g 1 2 3 4 5 6
[•]DMF
[t/]Mr,
d]/g
dl/g
0'18 0"21 0.29 0"38 0"41 0"45 0"47 0"51 0"54 0"56 0"63 0-65 0-66 0-71 0"73 0"75 0"75 0"77 0"81 0-89 0"90 0"92 1"19 1"23 0'64
-~w X 10 -a
PAE-1 0.18 0.21 0.31 0"47 0.50 0.52 0.57 0:60 0.63 0'64 0"69 0-70 0.71 0.76 0"81 0"83 0"83 0"86 0.91 0-99 1.00 1-03 1-28 1"33 0"77
A'~× 10~, cm3/g
SD X I0 la, cm/sec .dyne
7"8 8"0 17"0 34"0
40'0 36"00 36"0 34"5
1"7 2.2
42"0
33'4
2"5
59'0
18"2
2"7
67"5 75"0
16.2 14"7
3"1 3"2
83"0 111"0 125"0 55"0
14"6 15"5 16"0 27.0
3"4 3"8 3"9 2"8
1"6
* Lossin fractionationof PAE-1--5.6%and of PAE-2-3.1%. The occurrence of t w o sections with different slopes corresponding to the a b o v e molecular weight ranges is f o u n d also in the dependence of the second virial coefficient A~ on molecular weight (Fig. 3b). The occurrence of a n u m b e r of sections of different slope in the [~]-/14 relat i o n s h i p has been o b s e r v e d b y the a u t h o r s for o t h e r p o l y m e r s also [9]. The same p h e n o m e n o n has been r e p o r t e d in the literature for various classes of p o l y m e r s c o n t a i n i n g a r o m a t i c g r o u p s in the m a i n chain [10]. The a u t h o r s explain this b y t h e effect of the d e p e n d e n c e o f the configuration a n d p e r m e a b i l i t y o f t h e m a c r o m o l e c u l a r coils on molecular weight. Section I w i t h the e x p o n e n t a close t o u n i t y (0.84 a n d 0.90) corresponds a c c o r d i n g t o reference [10] to a free draining Gaussian coil or persistent chains. F o r t h e given P A E t h e e q u a t i o n b-~ (1 + a ) / 3 [11] does n o t hold. F r o m t h e SD ~ Mw e q u a t i o n b----0.57 a n d f r o m the e q u a t i o n m e n t i o n e d a b o v e 5----0.61 in section I.
Molecular w e i g h t characteristics of a cardic p o l y a m i d o e s t e r TABLE 1 Total w e i g h t -fract i o n of t h e fractions ZW~ ~- ~W~+1
Fraction No.
[~]DME,
[?]]MP,
dl/g
dl/g
0"18 0"24 0"30 0"35 0"37 0"43 0'50 0.54 0"54 0'55 0"57 0"58 0'59 0"60 0.65 0"66 0"66 0"68 0"71 0"73 0"76 0-81 O-98
0"18 0"24 0"30 0"37 0"42 0"46 0.54 0'55 0"55 0'57 0"59 0"60 0"63 0'66 0"69 0-70 0-70 0"74 0"76 0"78 0"81 0"91 1-04
0'53
0.74
2533
(cont.) .'42x 104, cmS/g
f4~, × 10 -3
SD × 1018, era/see'dyne
PAE-2 0"0115 0"0446 0"0887 0"1337 0"1857 0"2365 0'2829 0-3261 0'3642 0.4050 0.4511 0"4985 0'5472 0"5887 0"6256 0"6611 0"6964 0"7345 0'7740 0"8193 0"8678 0"9254 0'9783
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Original weight, - - 0 ' 5 g
7'8 12"0
40.0 35.0
1.6
29"5
34'0
2-1
45"0
32.1
2.5
47.0
29"8
2.6
59"0
18.2
2.7
67.5 91.0
16.2 14.5
3"1 3.6
48.0
~3"0
2.8
The divergence from this equation again indicates t h a t the molecular coils of this polymer have some permeability. The small volume effects, shown by the small difference in [7] in different solvents (Table 1) also supports the idea t h a t the coils are free draining. togfT/; 0"2 0
3. G i
i
a-# i
~
.W'~.2 I
318
,
*?
z
-0"2
lOgMw
-O'G -f'O --
a
t
b
Fzo. 2. D e p e n d e n c e of log [~] on log ~ w of t h e P A E in D M F (a) a n d M P (b).
2534
~rE. D. MOLODTSOVA. ~ al.
Section II of the curve of the [~/]D~F-~rw relationship in the molecular weigh~ region of 28,000-8000 has a slope characterized b y a value of a of 0.5, which accords to reference [10] corresponds to pseudo-0-conditions (A~ is very large
-12"5
-/
10g(ITz,1o*) f'8w
=-
"-
-¢J'0 /"0
log ~D
i 3"8
5.2 togas,
FIO. 3. Dependence of log SD (a) and log z~2 (b) on log ~rw of the PAE.
(Table 1) [11]). Then the coefficient K----22.22 × 10 -4 in equation I I a can be taken as K 0 and the Flory equation ~/M=(Ke/~)2/3[11] can be used for calculation of the unperturbed dimensions of the chain. In this w a y the length of the K u h n segment A was found to be 26.0/~. I~/0T
7"0 -
~ o - 2
36
•
0.5-
•.
!
•
."
20
O.Z q
H qO
80
IJO
FIo. 4. Lntegral (I, 2) and differential (I', 2") M ~ W D curves of P A E - I (I, I") and PA_E-2 (2, 2'), constructed from fractionation results.
Thus from the above results it m a y be concluded that the given polyamidoester has fairly flexible molecular chains, which at the same time form coils that are (possibly partially) free draining.
Molecular weight characteristics of a cardie polyamidoester
2535
The [~]-Mw e q u a t i o n t h a t we o b t a i n e d was used for c o n s t r u c t i n g M W D curves. I t is seen f r o m Fig. 4 t h a t t h e M W D curves show a u n i m o d a l distribution with a v e r a g e molecular weights close t o those m e a s u r e d e x p e r i m e n t a l l y (Table 2). Table 2 also shows the coefficients of p o l y d i s p e r s i t y Mw/Mn a n d ~Qz/2~w,calcul a t e d f r o m the M W D curves. The values of these coefficients indicate t h a t the M W D o f this P A E is c o m p a r a t i v e l y narrow. Very little information on the MWD of polymers prepared by low temperature polycondensation can be found in the literature and the results that are available are rather conflicting [12, 13]. As yet no theory has been developed that takes account of the effect of the various reactions occurring during preparation of the polymer, on its molecular weight and molecular weight distribution. An attempt was made in reference [14] to find the relationship between the nature of the reactions occurring in the synthesis of polymers and their molecular weight and molecular weight distribution. The authors consider various schemes of non-equilibrium polycondensation processes taking the theory of parallel (competing) reactions as the basis for quantitative discussion of such processes. Analysis of curves obtained with the aid of a computer enabled the authors to draw the conclusions that in all the schemes examined there is a strong dependence of molecular weight on the rate of side reactions and on the initial monomer ratio. In reference [15] theoretical approaches were made to low temperature (non-equilibrium) polycondensation processes involving reactions causing blocking of terminal functional groups. When compounds of high reactivity are used in low temperature polycondensation, such as acid chlorides of dibasic acids and diamines, the following blocking reactions are possible: hydrolysis of the acid chloride groups, formation of complexes of the acid chloride groups with amide solvents and protonation of the amino-groups. On the basis of equations derived by the authors they conclude that reactions causing blocking of functional groups bring about a decrease in the weight average degree of polycondensation and narrowing of the MWD. I t m a y be s u p p o s e d t h a t the conclusions r e a c h e d b y the a u t h o r s of reference [15] are q u a l i t a t i v e l y valid in our case also. I n f o r m a t i o n of the P A E discussed here, CIOC--~\--COOCHa n HaCOOC__Qg_COC1 +n .o
0 -
-o -f -cooc
7 q / \ o-
+ 2nHCI
0 u n d e r t h e conditions of low t e m p e r a t u r e p o l y c o n d e n s a t i o n in D M A A the following side reactions are possible t o some e x t e n t or a n o t h e r : h y d r o l y s i s o f acid chloride groups, f o r m a t i o n of complexes b e t w e e n acid chloride g r o u p s a n d DMAA, a n d r e a c t i o n of acid chloride groups w i t h d i m e t h y l a m i n e (which m a y be present
2536
YE. D. I~OLODTSOVAet al.
in trace quantities in DMAA). Here, because of the low reactivity of 2,5-dicarbomethoxyterephthalyl chloride, in comparison with terephthalyl chloride for example (possibly because of sterie hindrance), and the consequent higher reacTABLE 2.
i~OLECULAP~ WEIGHT
Polymer /I,~'w× 10-3* PAE-1 PAE-2
55.0 48.0
C H A 2 4 k C T E R I S T I C S OF P O L Y A B ~ I D O E S T E R S
~ × 10-8 , calculated from the i~WD curves 55.0 47.0
38.0 33.5
66.0 54.5
-~z/~w 1.4 1.4
1.2 1-15
* ~easured by Archibald's method.
tion temperature (5-10 °) than in the preparation of aromatic polyamides (--30 to 0 °) the importance of side reactions involving the acid chloride can be increased. These side reactions of the 2,5-dicarbomethoxyterephthalyl chloride can u p s e t the stoichiometric ratio of the monomers, result in blocking of the functional groups and chain termination on monofunctional compounds. The presence of small quantities of 2,4-dicarbomethoxyisophthalyl chloride and protonation of the amino-groulas of the 3,3-bis-(4-aminophenyl)phthalide can also disturb the equimolar ratio of the reactants and lead to termination of the polymer chain. Thus on the basis of evidence in the literature and of the molecular weights and coefficients of polydispersity obtained b y us for the PAE, it m a y be concluded that during the course of low temperature polycondensation the main polycondensation reaction is at all times accompanied b y slower side reactions that block the functional groups and cause termination of the polymer chains. I f the rate of the side reactions were commensurate with the rate of polycondensation we could not reach high degrees of reaction, therefore the rate of the side reactions must be considerably lower than the rate of polycondensation. Obviously side reactions causing blocking of functional groups begin to play a significant part when the concentration of functional groups, and consequently the probability of encounters between them, are sufficiently reduced. This permits the suggestion that in the case of the present polycondensation the most probable distribution with respect to molecular weight is produced b y the main polycondensation reaction, b u t gradual accumulation of "dead" chains as a result of termination on monofunctional compounds causes narrowing of the distribution. Translated by E. O. PHILLIPS REFERENCES
1. W. R. SORENSE, U.S.Pat. 3312663, 1967; RZhKhim., 25299P, 1969 2. S. NISHIZ.AK]"and T. MORIWAKI, J. Chem. Soc. J.apan 71: 1559, 1967 3. V. V. KORSHAK, S. V. VINOGRADOVA, Ya. S. VYGODSKII and Z. V. GERASH{~FIENKO, Vysokomol. soyed. A18: 1190, 1971 (Translated in Polymer Sci. U.S.S.R. 13: 5, 1341, 1971
Structure and reactivity of organic s~lts of hoxachloroantimoaic acid
2537
4. M. L. WALL&CH, J. Polymer Sci. A-2, 5: 653, 1967 5. A. V. PAVLOV, A. G. CHERNOVA a n d N. K. PINAYEVA, Vysokomol. soyed. BI4: 415, 1972 6. M. L. HAGGINS, J. Amer. Chem. Soe. 64: 2716, 1942 7. W. J. ARCHIBALD, J. Appl. Phys. 18: 362, 1947 8. W. J. ARCHIBALD, J. Phys. Colloid Chem. 51: 1204, 1947 9. V. M. MEN'SHOV, V. V. KORSHAK, G. I. TIMOFEYEVA and S. A. PAVLOVA, Vysokomol, soyed. AI4: 1766, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 8, 1978, 1972) 10. G. C. BERRY, H. MOMURA and K. G. MAYHAN, J. Polymer Sci. A-2, 5: 1, 1967 11. P. $. FLORY, Principles of Polymer Chemistry, New York, 1953 12. L. V. DUBROVINA, S. A. PAVLOVA, V. A. VASNEV, S. V. VINOGRADOVA and V. V. KORSHAK, Vysokomol. soyed. A12: 1308, 1970 (Translated in Polymer Sci. U.S.S.R. 12: 6, 1484, 1970) 13. V. V. KORSHAK and S. V. VINOGRADOVA, Vysokomol. soyed. A13: 367, 1971 (Translated in Polymer Sei. U.S.S.R. 13: 2, 415, 1971) 14. L. V. SOKOLOV, Yu. V. SHARIKOV and R. P. KOTLOVA, Vysokomol. soyed. AI2: 1934, 1970 (Translated in Polymer Sei. U.S.S.R. 12: 9, 2190, 1970) 15. I. K. NEKRASOV and S. Ya. FRENKEL', Dokl. Akad. Nauk SSSR 203: 1354, 1972
SPECTROPHOTOMETRIC STUDY OF THE STRUCTURE A N D REACTIVITY OF ORGANIC SALTS OF HEXACHLOROANTIMONIC ACID* V. t ). VOLKOV, E. F. OLEI~K, ¥C. N. SMm~OV, B. A. Ko~-~OV, A. I. YEFREM[OVA, B. A. I~OZENBERG a n d N. S. YENIKOLOPYA~ I n s t i t u t e of Chemical Physics, U.S.S.R. Academy of Sciences
(Received 12 March 1973) I n a study of the electronic spectra of onium and carbonium salts of hexachloroantimonic acid it has been found that the absorption band with 2max-~ 272 n m is produced b y electronic transitions in the free SbCl~ anion and in the ion pair R+SbCI~, and is independent of the nature of the cation. The cation strongly affects the stability of the SbCl[ anion. I t is shown t h a t earboxonium salts, which are active centres for polymerization of cyclic acetals or are formed in initiation of polymerization of tetrahydrofuran b y trityl hexachloroantimonate, are unstable and decompose reversibly to the molecular forms.
ORGAniC salts of hexachloroantimonic acid are used extensively as catalysts for polymerization of vinyl monomers [1-3] and heterocyclic compounds [4-9]. These salts show characteristie absorption in the ultraviolet region of the spee* Vysokomol. soyed. A16 No. 10, 2190-2195, 1974.
(Received 55 January 1973)
A study has been made of the molecular weight characteristics of a stable polyamidoester of high molecular weight, prepared b y low temperature polycondensation of 2,5-dicarboxymethoxyterephthalyl chloride with 3,3-bis-(4-aminophenyl) phthalide. The hydrodynamic properties of this polyamidoester were investigated and the length of the K u h n statistical segment of the polymer chain has been calculated. I t was found t h a t this polyamidoester, obtained b y low temperature polycondensation, has a molecular weight distribution narrower t h a n the most probable distribution.
THE TWO stage polyeondensation method is used extensively for preparation of polyheteroarylenes of different structure. I n the preparation polymides by the two stage method of polycondensation soluble polyamidoacids (PAA) are obtained in the first stage. I n the second stage, the stage of intramolecular cyclization, the production of polyimides of high molecular weight in a purely thermal process is made difficult by the occurrence of considerable hydrolysis of the PAA by the water evolved. I n order to eliminate the catalytic effect of carboxyl groups and to increase the stability of the amide linkage of these polymers, a method has been proposed for preparation of polyimides through polyamidoesters (PAE), as stable derivatives of PAA's, obtained by low temperature polycondensatiorl of diacid chloride of diesters of tetracarboxylic acids with primary aromatic diamines, in solution in an amide solvent [1-3]. The greater resistance to hydrolysis of PAE's, in comparison with PAA's, erlabtes polyimides of high molecular weight to be obtained from them [3] and they also provide the possibility of carrying out a thorough investigation of their molecular weight characteristics, a knowledge of which would assist in understanding the laws of low temperature polycondensation in amide solvents. At the s£me time there are grounds for supposing that the molecular weight characteristics of the original PAE are of decisive importance in determining the properties of the polyimide. There is no information in the literature on the molecular weight characteristics of P A E ' s and the molecular weight characteristics of PAA's, studied in detail in references [4] and [5], can scarcely be regarded as being sufficiently accurate in view of th instability of PAA's.
* Vysokomol. soyed. AI6: No. 10, 2183-2189, 1974. 2529
2530
YE. D. I~OLODTSOVAet
al.
The purpose of the present work was to investigate the molecular weight characteristics of a cardic polyamidoester of the structure -
_oc_,~\_coocm
~
-I
o
_L,
:,
prepared by low temperature polycondensation in DMAA. EXPERIMENTAL The P A E was prepared b y low temperature polycondensation of 2,5-dicarbomethyloxyterephthalyl chloride with 3,3-bis-(4-aminophenyl)phthalide in exactly e q u i ~ o l a r quantities in D~IAA, by the m e t h o d of reference [3]. The reaction was carried out for 30 min at 10 ° and 2 hr at room temperature. A t the end of the reaction the polymer was isolated by pouring a diluted solution into water. I t was filtered off. washed several times with water, then acetone, and dried in vacuo at room temperature. The yield of polymer was quantitative. The stability of the P A E was tested at room temperature in suitable solvents. On storage of a 0.4% solution of the P A E in D M F t/tea had not changed after 11 days. W h e n a 0.5%
70'yM~pp
2,0-
1"0
7"5/
b 1"0 ~
3
0"8
q
0.5
/
2/2/j¢,/E /All~ //.IB
i/ / .,/.,ZZ
.1;'..'2/' 0"2 t
J
O'E 1"0 c~g/d! t
t
t
O;Z
1 O-Z
I
I
0.6
I
L_
!-:
c, ~q/a/
FIo. I. Concentration dependence of the molecular weight (a) and sedimentation constant (b) of the P A E ' s and some of their fractions. Continuous l i n e s - - P A E - 1 , broken l i n e s - - P A E - 2. The figures on the curves are the fraction numbers, 0 represents the unfractionated P A E .
Molecular weight characteristics of a cardic polyamidoester
2531
solution of a fraction of the P A E in N-methyl-2-pyrrolidone (MP) was kept for 7 days qred was unchanged. W h e n a 1% solution of the P A E in a phenol-TCE mixture was stored t/tea (originally 2.05) was 2.02 after 32 days and 2.01 after 67 days. Consequently the P A E is stable in these solvents. Two samples of the P A E (PAE-1 and PAE-2) were used for the investigation. They were prepared under the same conditions a n d h a d the following characteristics: P A E - h [~/]DMF = 0 ' 6 4 dl/g, [~1~P=0"77 dl/g, 2Qw----55,000; PAE-2:[r/]D•F=0"53 dl/g, [~/]Mp=0"74 dl/g, /t),o = 48,000. The p o l y m e r samples were fractionated from a 1% solution b y distribution between two liquid phases in the T C E - p h e n o l - h e p t a n e system. To obtain more reliable results two parallel fractions were carried out. Five grammes of each polymer were fractionated into t w e n t y four and t w e n t y three fractions of PAE-1 and PAE-2 respectively. The weight of the fractions was about 0.2 g. PAE-1 was first separated into several large fractions, each of which was then refractionated. I n the ease of PAE-2 each fraction was obtained successively in the course of the main fractionation. The viscosity of the original polymer and of all the fractions was measured in D M F a n d MP a t 25±0.05% at four concentrations in the 0.4-1.0 g/dl range in a suspended-level viscometer. The flow time of the solvent was 100-130 sec. The intrinsic viscosity [t/] was found by double graphical extrapolation of the curves of the Huggins equation to infinite dilution [6]. Sedimentation analyses were obtained in MOM (Hungary) 3170 a n d G-120 analytical ultracentrifuges, at a rotor t e m p e r a t u r e of 25q-0.1 °. The solvent for sedimentation analysis was DMF. " A p p a r e n t " molecular weights, M~pp were determined at four concentrations in the range of 0.2-0.7 g/dl, b y the unstable equilibrium method [7, 8]. The rotor speed was chosen so t h a t the gradient curve intersected the meniscus at a sufficiently large angle. The true molecular weight /ff/w was found b y graphical extrapolation of 1 / M ~ pp to infinite dilution (Fig. 1 (a). The specific p a r t i a l volume v of the polymer in DMF, measured in a pyknometer, was 0-704 cma/g, the density of D M F p = 0.947 g/era a. The sedimentation coefficient Sc of the original P A E and of the fractions was measured a t a rotor speed of ~ 50,000 rev/min at four concentrations in the range of 0-2-0-7 dl/g. The sedimentation constant SD were obtained b y graphical extrapolation to infinite dilution (Fig. 1 b). The results of fractionation and the molecular weight characteristics of the fractions are presented in Table 1. RESULTS AND DISCUSSION
I t is s e e n f r o m T a b l e 1 t h a t [~/] o f t h e P A E f r a c t i o n s i n D M F v a r i e s b e t w e e n 0.18 a n d 1.23 d l / g , a n d t h e m o l e c u l a r w e i g h t s f r o m 7800 t o 125,000. F r o m t h i s it may be concluded that fractionation of the polymers occurred with good selectivity. The log-log graphs of the relationship between the intrinsic viscosibies and m o l e c u l a r w e i g h t s o f t h e P A E f r a c t i o n s i n D M F a n d M P ( F i g . 2) h a v e t w o sections with different slopes and are described by the following equations: in the 1 2 5 , 0 0 0 - 2 8 , 0 0 0 m o l e c u l a r w e i g h t r e g i o n [~/]DMF----0"65× 1 0 - 4 × ~ S 4 ( I a ) a n d [r/]Me~--0-38 × 1 0 - 4 x 2tTr°'9° ( I b ) , a n d in t h e 2 8 , 0 0 0 - 8 0 0 0 m o l e c u l a r w e i g h t r e g i o n [r/]DMF=22"22 × 1 0 - 4 × /l~f°w"5° ( I I a ) a n d [~/]Mp= 16.62 × 1 0 - 4 x / Q ~ a ( I I b ) . The relationship between the sedimentation constants and molecular weights o f t h e P A E f r a c t i o n s i n t h e m o l e c u l a r w e i g h t r e g i o n o f 1 2 5 , 0 0 0 - 2 8 , 0 0 0 (Fig. 3a) is e x p r e s s e d b y t h e e q u a t i o n S D = 2 " 5 4 x 10 ~5 ×/t~Ow.a3.
2532
Y~. D. MOLODTSOVAet al. TABLE 1. ~AOTIONATION OF THE POLYAMIDO:ESTERSAMPLES*
Fraction No.
Total weight-fraction of thefractions ZW~+½W~+I
0.0077 0.0348 0-0752 0-1206 0-1691 0.2176 0.2637 7 0.3086 8 0.3429 9 0.3909 10 11 0.4452 12 0.4913 0.5473 13 0.6040 14 0.6581 15 16 0.7081 0.7528 17 0.7944 18 19 0"8314 0.8554 20 0.8803 21 22 0-9132 0.9459 23 0-9806 24 Orginal weight -- 5"0 g 1 2 3 4 5 6
[•]DMF
[t/]Mr,
d]/g
dl/g
0'18 0"21 0.29 0"38 0"41 0"45 0"47 0"51 0"54 0"56 0"63 0-65 0-66 0-71 0"73 0"75 0"75 0"77 0"81 0-89 0"90 0"92 1"19 1"23 0'64
-~w X 10 -a
PAE-1 0.18 0.21 0.31 0"47 0.50 0.52 0.57 0:60 0.63 0'64 0"69 0-70 0.71 0.76 0"81 0"83 0"83 0"86 0.91 0-99 1.00 1-03 1-28 1"33 0"77
A'~× 10~, cm3/g
SD X I0 la, cm/sec .dyne
7"8 8"0 17"0 34"0
40'0 36"00 36"0 34"5
1"7 2.2
42"0
33'4
2"5
59'0
18"2
2"7
67"5 75"0
16.2 14"7
3"1 3"2
83"0 111"0 125"0 55"0
14"6 15"5 16"0 27.0
3"4 3"8 3"9 2"8
1"6
* Lossin fractionationof PAE-1--5.6%and of PAE-2-3.1%. The occurrence of t w o sections with different slopes corresponding to the a b o v e molecular weight ranges is f o u n d also in the dependence of the second virial coefficient A~ on molecular weight (Fig. 3b). The occurrence of a n u m b e r of sections of different slope in the [~]-/14 relat i o n s h i p has been o b s e r v e d b y the a u t h o r s for o t h e r p o l y m e r s also [9]. The same p h e n o m e n o n has been r e p o r t e d in the literature for various classes of p o l y m e r s c o n t a i n i n g a r o m a t i c g r o u p s in the m a i n chain [10]. The a u t h o r s explain this b y t h e effect of the d e p e n d e n c e o f the configuration a n d p e r m e a b i l i t y o f t h e m a c r o m o l e c u l a r coils on molecular weight. Section I w i t h the e x p o n e n t a close t o u n i t y (0.84 a n d 0.90) corresponds a c c o r d i n g t o reference [10] to a free draining Gaussian coil or persistent chains. F o r t h e given P A E t h e e q u a t i o n b-~ (1 + a ) / 3 [11] does n o t hold. F r o m t h e SD ~ Mw e q u a t i o n b----0.57 a n d f r o m the e q u a t i o n m e n t i o n e d a b o v e 5----0.61 in section I.
Molecular w e i g h t characteristics of a cardic p o l y a m i d o e s t e r TABLE 1 Total w e i g h t -fract i o n of t h e fractions ZW~ ~- ~W~+1
Fraction No.
[~]DME,
[?]]MP,
dl/g
dl/g
0"18 0"24 0"30 0"35 0"37 0"43 0'50 0.54 0"54 0'55 0"57 0"58 0'59 0"60 0.65 0"66 0"66 0"68 0"71 0"73 0"76 0-81 O-98
0"18 0"24 0"30 0"37 0"42 0"46 0.54 0'55 0"55 0'57 0"59 0"60 0"63 0'66 0"69 0-70 0-70 0"74 0"76 0"78 0"81 0"91 1-04
0'53
0.74
2533
(cont.) .'42x 104, cmS/g
f4~, × 10 -3
SD × 1018, era/see'dyne
PAE-2 0"0115 0"0446 0"0887 0"1337 0"1857 0"2365 0'2829 0-3261 0'3642 0.4050 0.4511 0"4985 0'5472 0"5887 0"6256 0"6611 0"6964 0"7345 0'7740 0"8193 0"8678 0"9254 0'9783
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Original weight, - - 0 ' 5 g
7'8 12"0
40.0 35.0
1.6
29"5
34'0
2-1
45"0
32.1
2.5
47.0
29"8
2.6
59"0
18.2
2.7
67.5 91.0
16.2 14.5
3"1 3.6
48.0
~3"0
2.8
The divergence from this equation again indicates t h a t the molecular coils of this polymer have some permeability. The small volume effects, shown by the small difference in [7] in different solvents (Table 1) also supports the idea t h a t the coils are free draining. togfT/; 0"2 0
3. G i
i
a-# i
~
.W'~.2 I
318
,
*?
z
-0"2
lOgMw
-O'G -f'O --
a
t
b
Fzo. 2. D e p e n d e n c e of log [~] on log ~ w of t h e P A E in D M F (a) a n d M P (b).
2534
~rE. D. MOLODTSOVA. ~ al.
Section II of the curve of the [~/]D~F-~rw relationship in the molecular weigh~ region of 28,000-8000 has a slope characterized b y a value of a of 0.5, which accords to reference [10] corresponds to pseudo-0-conditions (A~ is very large
-12"5
-/
10g(ITz,1o*) f'8w
=-
"-
-¢J'0 /"0
log ~D
i 3"8
5.2 togas,
FIO. 3. Dependence of log SD (a) and log z~2 (b) on log ~rw of the PAE.
(Table 1) [11]). Then the coefficient K----22.22 × 10 -4 in equation I I a can be taken as K 0 and the Flory equation ~/M=(Ke/~)2/3[11] can be used for calculation of the unperturbed dimensions of the chain. In this w a y the length of the K u h n segment A was found to be 26.0/~. I~/0T
7"0 -
~ o - 2
36
•
0.5-
•.
!
•
."
20
O.Z q
H qO
80
IJO
FIo. 4. Lntegral (I, 2) and differential (I', 2") M ~ W D curves of P A E - I (I, I") and PA_E-2 (2, 2'), constructed from fractionation results.
Thus from the above results it m a y be concluded that the given polyamidoester has fairly flexible molecular chains, which at the same time form coils that are (possibly partially) free draining.
Molecular weight characteristics of a cardie polyamidoester
2535
The [~]-Mw e q u a t i o n t h a t we o b t a i n e d was used for c o n s t r u c t i n g M W D curves. I t is seen f r o m Fig. 4 t h a t t h e M W D curves show a u n i m o d a l distribution with a v e r a g e molecular weights close t o those m e a s u r e d e x p e r i m e n t a l l y (Table 2). Table 2 also shows the coefficients of p o l y d i s p e r s i t y Mw/Mn a n d ~Qz/2~w,calcul a t e d f r o m the M W D curves. The values of these coefficients indicate t h a t the M W D o f this P A E is c o m p a r a t i v e l y narrow. Very little information on the MWD of polymers prepared by low temperature polycondensation can be found in the literature and the results that are available are rather conflicting [12, 13]. As yet no theory has been developed that takes account of the effect of the various reactions occurring during preparation of the polymer, on its molecular weight and molecular weight distribution. An attempt was made in reference [14] to find the relationship between the nature of the reactions occurring in the synthesis of polymers and their molecular weight and molecular weight distribution. The authors consider various schemes of non-equilibrium polycondensation processes taking the theory of parallel (competing) reactions as the basis for quantitative discussion of such processes. Analysis of curves obtained with the aid of a computer enabled the authors to draw the conclusions that in all the schemes examined there is a strong dependence of molecular weight on the rate of side reactions and on the initial monomer ratio. In reference [15] theoretical approaches were made to low temperature (non-equilibrium) polycondensation processes involving reactions causing blocking of terminal functional groups. When compounds of high reactivity are used in low temperature polycondensation, such as acid chlorides of dibasic acids and diamines, the following blocking reactions are possible: hydrolysis of the acid chloride groups, formation of complexes of the acid chloride groups with amide solvents and protonation of the amino-groups. On the basis of equations derived by the authors they conclude that reactions causing blocking of functional groups bring about a decrease in the weight average degree of polycondensation and narrowing of the MWD. I t m a y be s u p p o s e d t h a t the conclusions r e a c h e d b y the a u t h o r s of reference [15] are q u a l i t a t i v e l y valid in our case also. I n f o r m a t i o n of the P A E discussed here, CIOC--~\--COOCHa n HaCOOC__Qg_COC1 +n .o
0 -
-o -f -cooc
7 q / \ o-
+ 2nHCI
0 u n d e r t h e conditions of low t e m p e r a t u r e p o l y c o n d e n s a t i o n in D M A A the following side reactions are possible t o some e x t e n t or a n o t h e r : h y d r o l y s i s o f acid chloride groups, f o r m a t i o n of complexes b e t w e e n acid chloride g r o u p s a n d DMAA, a n d r e a c t i o n of acid chloride groups w i t h d i m e t h y l a m i n e (which m a y be present
2536
YE. D. I~OLODTSOVAet al.
in trace quantities in DMAA). Here, because of the low reactivity of 2,5-dicarbomethoxyterephthalyl chloride, in comparison with terephthalyl chloride for example (possibly because of sterie hindrance), and the consequent higher reacTABLE 2.
i~OLECULAP~ WEIGHT
Polymer /I,~'w× 10-3* PAE-1 PAE-2
55.0 48.0
C H A 2 4 k C T E R I S T I C S OF P O L Y A B ~ I D O E S T E R S
~ × 10-8 , calculated from the i~WD curves 55.0 47.0
38.0 33.5
66.0 54.5
-~z/~w 1.4 1.4
1.2 1-15
* ~easured by Archibald's method.
tion temperature (5-10 °) than in the preparation of aromatic polyamides (--30 to 0 °) the importance of side reactions involving the acid chloride can be increased. These side reactions of the 2,5-dicarbomethoxyterephthalyl chloride can u p s e t the stoichiometric ratio of the monomers, result in blocking of the functional groups and chain termination on monofunctional compounds. The presence of small quantities of 2,4-dicarbomethoxyisophthalyl chloride and protonation of the amino-groulas of the 3,3-bis-(4-aminophenyl)phthalide can also disturb the equimolar ratio of the reactants and lead to termination of the polymer chain. Thus on the basis of evidence in the literature and of the molecular weights and coefficients of polydispersity obtained b y us for the PAE, it m a y be concluded that during the course of low temperature polycondensation the main polycondensation reaction is at all times accompanied b y slower side reactions that block the functional groups and cause termination of the polymer chains. I f the rate of the side reactions were commensurate with the rate of polycondensation we could not reach high degrees of reaction, therefore the rate of the side reactions must be considerably lower than the rate of polycondensation. Obviously side reactions causing blocking of functional groups begin to play a significant part when the concentration of functional groups, and consequently the probability of encounters between them, are sufficiently reduced. This permits the suggestion that in the case of the present polycondensation the most probable distribution with respect to molecular weight is produced b y the main polycondensation reaction, b u t gradual accumulation of "dead" chains as a result of termination on monofunctional compounds causes narrowing of the distribution. Translated by E. O. PHILLIPS REFERENCES
1. W. R. SORENSE, U.S.Pat. 3312663, 1967; RZhKhim., 25299P, 1969 2. S. NISHIZ.AK]"and T. MORIWAKI, J. Chem. Soc. J.apan 71: 1559, 1967 3. V. V. KORSHAK, S. V. VINOGRADOVA, Ya. S. VYGODSKII and Z. V. GERASH{~FIENKO, Vysokomol. soyed. A18: 1190, 1971 (Translated in Polymer Sci. U.S.S.R. 13: 5, 1341, 1971
Structure and reactivity of organic s~lts of hoxachloroantimoaic acid
2537
4. M. L. WALL&CH, J. Polymer Sci. A-2, 5: 653, 1967 5. A. V. PAVLOV, A. G. CHERNOVA a n d N. K. PINAYEVA, Vysokomol. soyed. BI4: 415, 1972 6. M. L. HAGGINS, J. Amer. Chem. Soe. 64: 2716, 1942 7. W. J. ARCHIBALD, J. Appl. Phys. 18: 362, 1947 8. W. J. ARCHIBALD, J. Phys. Colloid Chem. 51: 1204, 1947 9. V. M. MEN'SHOV, V. V. KORSHAK, G. I. TIMOFEYEVA and S. A. PAVLOVA, Vysokomol, soyed. AI4: 1766, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 8, 1978, 1972) 10. G. C. BERRY, H. MOMURA and K. G. MAYHAN, J. Polymer Sci. A-2, 5: 1, 1967 11. P. $. FLORY, Principles of Polymer Chemistry, New York, 1953 12. L. V. DUBROVINA, S. A. PAVLOVA, V. A. VASNEV, S. V. VINOGRADOVA and V. V. KORSHAK, Vysokomol. soyed. A12: 1308, 1970 (Translated in Polymer Sci. U.S.S.R. 12: 6, 1484, 1970) 13. V. V. KORSHAK and S. V. VINOGRADOVA, Vysokomol. soyed. A13: 367, 1971 (Translated in Polymer Sei. U.S.S.R. 13: 2, 415, 1971) 14. L. V. SOKOLOV, Yu. V. SHARIKOV and R. P. KOTLOVA, Vysokomol. soyed. AI2: 1934, 1970 (Translated in Polymer Sei. U.S.S.R. 12: 9, 2190, 1970) 15. I. K. NEKRASOV and S. Ya. FRENKEL', Dokl. Akad. Nauk SSSR 203: 1354, 1972
SPECTROPHOTOMETRIC STUDY OF THE STRUCTURE A N D REACTIVITY OF ORGANIC SALTS OF HEXACHLOROANTIMONIC ACID* V. t ). VOLKOV, E. F. OLEI~K, ¥C. N. SMm~OV, B. A. Ko~-~OV, A. I. YEFREM[OVA, B. A. I~OZENBERG a n d N. S. YENIKOLOPYA~ I n s t i t u t e of Chemical Physics, U.S.S.R. Academy of Sciences
(Received 12 March 1973) I n a study of the electronic spectra of onium and carbonium salts of hexachloroantimonic acid it has been found that the absorption band with 2max-~ 272 n m is produced b y electronic transitions in the free SbCl~ anion and in the ion pair R+SbCI~, and is independent of the nature of the cation. The cation strongly affects the stability of the SbCl[ anion. I t is shown t h a t earboxonium salts, which are active centres for polymerization of cyclic acetals or are formed in initiation of polymerization of tetrahydrofuran b y trityl hexachloroantimonate, are unstable and decompose reversibly to the molecular forms.
ORGAniC salts of hexachloroantimonic acid are used extensively as catalysts for polymerization of vinyl monomers [1-3] and heterocyclic compounds [4-9]. These salts show characteristie absorption in the ultraviolet region of the spee* Vysokomol. soyed. A16 No. 10, 2190-2195, 1974.