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The kinetics of intramolecular cyclization of polyisoprene
Kinetics of intramolecular cyclization of polyisoprene
1145
(3) A radical mechanism of vulcanization of elastomers in the presence of the complexes is proposed, whereby as a result of addition of the complex to the rubber and the occurrence of polymerization, polyfunctional crosslinkages are formed, linking the rubber molecules by both covalent and coordinate bonds. Translated by E. O. PHILLIPS REFERENCES 1. A. A. DONTSOV, G. K. LOBACHEVA and B. A. DOGADKIN, K a u c h u k i rezina, No. 2, 19, 1968 2. B. A. DOGADKIN, A. A. DONTSOV and G. K. LOBACHEVA, Rus. Pat. (Authors' Certificate), 215477, Byull. izobret., No. 13, 78, 1968 3. N. D. Zfl,KH~tROV, Novye t i p y sinteticheskikh k a u c h u k o v v oblasti ikh prakticheskogo ispol'zovaniya (New Types of Synthetic R u b b e r and their Fields of Practical Application). p. 104, TSBTI, Yaroslavl', 1962 4. A. A. DONTSOV, G. K. LOBACHEVA, A. A. PODZHUNAS, A. A. RYBAKOV and B. A. DOGADKIN, K a u c h u k i rezina, No. 11, 3, 1968 5. H. GROSSMAN, Ber. 37: 1225, 1904 6. A. A. DONTSOV, G. K. LOBACHEVA and B. A. DOGADKIN, Kolloid. zh. 29 : 445, 1967 7. S. M. GUBRELL, L. MIfLLINS a n d R. S. RIVLIN, Trans. F a r a d a y Soc. 49: 1495, 1953 8. L. M. KURACHENKOVA and A. G. SHVARTS, Vysokomol. soyed. B10: 104, 1968 (Not translated in Polymer Sci. U.S.S.R.) 9. A. A. DONTSOV, G. K. LOBACHEVA a n d B. A. DOGADgIN, Vysokomol. soyed. A l l : 2370, 1969 (Translated in P o l y m e r Sei. U.S.S.R. 11: 11, 2689, 1969) 10. A. D. DONTSOV, V. F. SOLDATOV, A. N. KAMENSKII and B. A. DOGADKIN, Kolloid. zh. 31: 370, 1969
THE KINETICS OF INTRAMOLECULAR CYCLIZATION OF POLYISOPRENE* I. A. TUTO~SKU, E. G. BOIKACHEVA, I. G. BUKA:gOV and B. A. DOGADKIN M. V. Lomonosov I n s t i t u t e of F i n e Chemical Technology, Moscow
(Received 24 January 1969)
As A RESULTof extensive use of the spectroscopic method of study of the structure of the products of eyclization of polyisoprene [1] and polybutadiene [2] it has become possible to determine such structural characteristics of cyclized rubbers as the type of double bonds present and the number of rings in a block. Study of the kinetics of change of these characteristics during the cyclization process * Vysokomol. soyed. A12: No. 5, 1013-1021, 1970.
1146
I . A . TUTORSKIIet al.
provides a d e e p e r u n d e r s t a n d i n g o f t h e m e c h a n i s m o f this complex reaction. T h e p u r p o s e o f t h e present work is to elucidate t h e kinetics o f cyclization o f polyisoprene c a t a l y s e d b y t h e p h o s p h o r u s p e n t o x i d e - p h e n o l system. EXPERIMENTA L
The cyclization of SKI-3 synthetic polyisoprene (molecular weight 126,000, content of c/a-double bonds 95 %) was studied in a 1 : 1 mixture ofxylene and phenol. The concentration of the polymer solution was 15.4% (2.205 mole/1.), the concentration of catalyst was varied between 3 and 9% of the weight of the rubber and the temperature was varied between 60 and 140°. The reaction was conducted in an atmosphere of dry carbon dioxide. The cyclized rubber in test samples of the solution was precipitated by methanol, redissolved in benzene, reprecipitated by methanol and dried in vacuo at 60°. The course of the reaction was followed by the variation in total unsaturation, determined by reaction with perbenzoic acid, and by the variation in the intensity of infrared absorption bands and of the peaks of high-resolution NMR spectra. The infrared spectra were recorded in the 500-3100 cm -1 region in a UR-10 do~blebeam spectrograph. The specimens were prepared by compressing the cyclized rubber between pieces of copper foil at 120° and a pressure of 150 arm, then removing the foil by etching with a 10% solution of ammonium persulphate. This produced films of the polymer of thickness 20-30/~, framed by copper foil. The band at 1378 cm -1 (symmetrical deformation vibrations of C--H in thei~C--CH s _ group) was used as an internal reference. The mean square error in determinat on of the relative intensity of the relative optical density of the 840 cm -1 band was 5-7%. The high-resolution 17MR spectra were recorded in the radiospectrometer of the Central Automation Laboratory (CAL) (60 MHz) [3]. The solvent was CC14and the internal reference was hexamethylsiloxane. The concentration of polymer in the solution was varied between 4 and 7%, depending on the viscosity of the solution, and the spectra were recorded at 90 ° RESULTS AND DISCUSSION
I t was shown in reference [4] t h a t d u r i n g the course o f cyclization the conc e n t r a t i o n o f c i s - l , 4 double bonds in linear segments decreases, double bonds in rings a p p e a r a n d individual c o m p o n e n t s o f t h e c a t a l y s t s y s t e m and solvent (for example, phenol) a d d to t h e polymer. F i g u r e l a shows t h e kinetics o f d i s a p p e a r a n c e o f cis-l,4 double bonds during cyclization o f SKI-3, d e t e r m i n e d b y infrared spectroscopy. I t is seen t h a t w i t h i n the studied t e m p e r a t u r e range t h e r a t e o f the r e a c t i o n leading to disappearance o f linear double bonds increases s h a r p l y w i t h increase in t e m p e r a t u r e . F i g u r e lb shows t h e kinetics o f f o r m a t i o n o f ring double bonds. Since b y d e p r o t o n i z a t i o n a double b o n d can be f o r m e d in one o f t h r e e positions: ~ '
~//~x~ °r ~
'
the n u m b e r of ring double bonds was calculated as the difference b e t w e e n t h e t o t a l d o u b l e - b o n d content, d e t e r m i n e d w i t h perbenzoic acid, a n d t h e c o n t e n t o f linear double bonds d e t e r m i n e d b y m e a n s o f t h e 840 cm -1 b a n d in the infrared s p e c t r u m . T h e calculated results are given in T a b l e 1.
Kinetics of intramolecular cyclization of polyisoprene
1147
In the initial stage of the reaction (up to 30 rain) (Fig. lb) the rate of formation of ring double bonds increases with increase in temperature, b u t at a high degree of cyelization and at high temperatures (100 and 140 °) the limiting quantity of /7£~%
80
80
:\ n~,%l
o
[]
b
= 2
40
#
0
I
#
8
i
Time, hp.
"
i
12
I
I
16
I
I 20
FIG. 1. Variation in the number of linear ci#.l,4 (a) and ring (b) double bonds during eyclization. Concentration of P205--7"5% by weight. 1--60°; 2--80 °, 3-100°, 4--140°; n+, is the percentage of linear and nR of ring double bonds. ring double bonds being formed begins to decrease. This indicates that the double bonds in monocyclic units become reactivated, forming the bi- and polycyclic structures that we have discussed previously [4]. Figure 2 shows the kinetics of disappearance of cis-l,4 double bonds during cyclization at 140 ° with different concentrations of catalyst. The rate of disappearance of linear double bonds increases as the concentration of catalyst is increased. Figure 3 shows the kinetics of change in the relative intensity of the 750 cm -I band, corresponding to phenol combined in the ortho-position. Both the rate of addition of phenol and the limiting quantity added increase with increase in temperature. The order of reaction in the initial stage of cyclization under various experimental conditions was determined b y the differential method, using the equation w = # . c n, where w is the reaction rate, k the rate constant, c the concentration of double bonds and n the order of reaction.
1148
I. A. TUTORSKII et aL T~LBLE 1. K n ~ T I C S Or CYCLIZATION OF POLYISOPRENE
T i m e o f cyclization, hr
ConcentraConcentration of [ Number of tion of • ing d o u b l e rings, linear double n b o n d s [L], % b o n d s [R], %
%
140°; [PaOs]--7-5 w t . 0.5 1.0 2.0 3.0 12.0
26"4 10.2 2.0 1-8
40"0 44-8 45"2 40"7 31"0
0.8 I-0 1.2 1.4 2.2
lOOO;[P,0~]-7.5 wt.% 0.5 1.0 2-0 3.0 4.0 5.0 13.0
46"2 39.3 16"4 8"8 8"0 7'2
29.3 28.1 40.1 38.2 36.2 30-0 27.8
0.8 1.2 1.1 1.4 1-5 2.1 2.6
80°; [ P 2 0 5 ] - - 7 " 5 w t . % 1.0 2.0 3.0 5.0 7.0 10-0 14-0 18.0 26.0
48"5 27"0 17"9 5-3 2-6 1"5 2.6 2"3 1.3
31.7 47.6 49"9 49"3 54"4 49-3 45.2 46"0 44-6
0.6 0.5 0.6 0.9 0.8 1.0 1.2 1.1 1.2
60°; [P~05] -- 7"5 w t . % 15"0 20"0 30"0
45"1 21-0 18.5
24"7 42.4 41.9
1.2 0.9 0.9
140°; [P~O5]--3-7 w t . % 1.0 1.5 2.0 3.0 4.0 11.0
62.6 29"8 16"4 9"1 1"5
21.1 42.2 44"3 46.1 50.2 46.3
0.3 0.7 0"9 1.0 1.0 1.2
140°; [PzOa]--9"O w t . % 0-5 1.0 12.0
13.6 4.8 --
38-7 42.8 30.7
1-2 1.2 2.3
Kinetics of intramolecular cyclization of polyisoprene
1149
The dependence of the initial rate of cyclization on the initial concentration of double bonds is represented by a straight line when plotted as log (zlc]At) against log c (Fig. 4). The slope of this line gives the order of reaction. n~,% fO0 80 60 40 20
0
4
8 Time , hp
12
FIG. 2. Variation in the content of linear c/s-l,4 double bonds during cyclization at 140 °. Concentration of P~05, % b y weight: 1--9.0, 2--7.5, 3--3.7.
Calculated values of the order of the initiation reaction are given in Table 2 for various reaction conditions, from which it is seen that these values are close to unity. I)75o/D,378 I
•
..K--.
x
0
I
2
I
I
I
.I
fO
8
i
I
!
14
I
/8
T i m e , hn FIG. 3. Variation in the relative optical density of the 750 em -1 b a n d (phenol combined in the o-position) during cyclization. Temperature, °C: 1-3--140, 4--100,
5--80. Concentration of P=Os, % by weight: •--9.0, 2, 4, 5--7.5, 3--3-7. The rate constants were calculated from the first order equation. These values are given in Table 3. The initiation rate constant is directly proportional to the catalyst concentration (Fig. 5a). The apparent energy of activation for cyclization, found graphically from the Arrhenius equation,is N 5.2 kcal/mole (Fig. 5b). This is in satisfactory agreement with the value 7 keal/mole found by pyrolytic gas chromatography [5].
1150
I. A. TUTORSXII et al.
The cyclization of diene polymers can be divided into the stages of initiation (formation of active centres), cyclization (propagation), deprotonization (chain termination) and re-initiation (activation of the ring double bonds formed) [1, 6]. According to this the cyclization process can be described by the set of differential equations: d~]---- b~[L] [H +]q-be[He +]
(1)
d [HC+] - - b,[L] [H+] +bIH +] [C]--k,[HC +]
(2)
dt
d [C] dt =--k'[H+] [C] +kt[HC +]
(3)
where [L] and [C] are the concentrations of linear and rings double bonds respectively, k~ is the initiation rate constant, k2 the rate constant of re-initiation, ks the rate constant of cyclization and k t the termination rate constant. TABLE 2. CALCULATED VALUES OF THE ORDER OF THE INITIATION REACTIOI~ !
Temperature Catalyst concen)f e y c l i z a t i o n , t r a t i o n (mole/mole o f S K I - 3 ) × 10 -~ °C
Order of Temperature Catalyst concenr e a c t i o n , o f cyclization, t r a t i o n (mole/mole n o f S K I - 3 ) x 10 -~ °C
3"59 3"59 3.59
60 80 100
1.15 1"05 0"985
I
140 140 140
3.59 1.78 4.24
Order of reaction, n 0.936 1.10 [ 0.96
For the steady-state period of cyclization we can assume that d [HC+]/dt=O. Then from equation (2) we obtain: [ H e +] =
b.,[H÷] [L] +kiH +] [13]
(4)
After substitution of (4) in (1) and (2) we obtain: _ _ _[L]=bl[H+ d ] [L ] + ~b~ (bill+ ] [L] +b2[H+] [(3])
(5)
= - - k , [ H +] [C] +b~[H +] [L] +k,[H +] [C]= k~[H+] [L].
(6)
dt
die/
dt
Assum~ug that bl----k2 we obtain:
ddt[L]__bx[H+][L] + ~ (bl[H+] [L]--k~[H+] [C])*
(7)
• T h e e x p r e s s i o n o b t a i n e d for c y c l i z a t i o n o f p o l y b u t a d i e n e in ref. [2] h a s a d i f f e r e n t f o r m b e c a u s e t h e a u t h o r s m a d e a n e r r o r i n its d e r i v a t i o n .
Kinetics of intraanolecular eyelization of polyisoprcne
1151
W e f o u n d kc/k t a n d kl[H +] f r o m expressions (6) and (7). Differentiation was carried o u t according to t h e formula: 1 Y~=~-h (--Yo+Y~) where Y0, Yl a n d y~ are t h e values o f t h e functions at e q u i d i s t a n t points [7].
TABLE 3.DETERMINATIONOF C Y C L I Z A T I O I N 7
:RATE COI~STAlffTS
Temperature (Moles P,O,/ Ik 2 X 3 log[A.]ITemperatur. (MolesP2OJ/k of cycliza/mole of ~ = tion, °C SKI-3) × 10-3/ 140 100 80 60
3.59 3.59 3.59 3.59
2×31o [A0] t [-~1]' of cycliza/mole of / = ~ g[A~]' rain -1 tion, °C SKI-3) × 10-2/ rain -~
0.0133 0.00932 0.0043 0-00287
140 140 140
0.00361 0.0133 0.0169
1.78
3.59 4.24
The ratios o f the cyclization r a t e c o n s t a n t to the t e r m i n a t i o n r a t e c o n s t a n t a n d t h e p r o d u c t s o f t h e i n i t i a t i o n r a t e c o n s t a n t (kc/kt) a n d the h y d r o g e n - i o n c o n c e n t r a t i o n (kl[H+]) for various conditions o f cyclization are given in Table 4.
lo 9 c , 10-2, m o l e l l .
0
8
I
I
I
16 I
2¢
I
I
I
I
32 I
-2.0 f~
-2.2-
n
•
•
,
0
o
X
-2"¢
C/o
/o
FIG. 4. Determination of the order of reaction' in the cyclization of polyisoprene. Temperature, °C: 1, 4, 5--140, 2--100, 3--80. Concentration of P205, °/o by weight: 1-3--7.5, 4--3.7, 5--9.0. T h e p r o d u c t k l [ i +] increases as the t e m p e r a t u r e a n d c a t a l y s t c o n c e n t r a t i o n are increased. No clear effect o f t e m p e r a t u r e on t h e ratio o f t h e cyclization r a t e
1152
I. A. TuToRsxII et at.
c o n s t a n t to t h e t e r m i n a t i o n r a t e c o n s t a n t is seen because o f t h e short d u r a t i o n o f t h e s t e a d y - s t a t e period. This ratio remains c o n s t a n t w h e n t h e c a t a l y s t concentrat i o n is increased. k,fO'~,rnZn'1 2.4
2.8
I
1.8f
a
3
3.0 I/'T,~O-3
I
I
b
logk
-2"0
1.#
2.8
I
30
-2"2
,.of
-2.#
O'2 .01
I
i I O'O3 molo P2Os/molo 8/
I
-2.6
O'O5
FIG. 5. Dependence of the initial rate constant on catalyst concentration at 140° (a) and on temperature (b). a-- Concentration of P=O5 (mole/mole of SKI-3): 1--1.78 × × 10-2, 2--3.59× 10-% 3--4.24× 10-=; b--~emperature, °C: •--60, 2--80, 3--100, 4-- 140. Concentration of P=O6--7"5~o by weight. The r a t i o kc//ct defines the n u m b e r o f rings in a cyclic block a n d in the e a r l y stages o f cyclization it agrees satisfactorily with t h e value o f n (Table 1). These values indicate t h e f o r m a t i o n o f monocyclic s t r u c t u r e s in t h e initial stage o f cyclization, w i t h a later change t o hi- a n d polycyclic structures. _7_" 0"5
D
0"3 0"2
~.~
v 3
0"1 " I
2
J
#
5
6
'I
5" /2
1#
Time, hr,
FIG. 6. Variation in the relative intensity of NMR peaks from protons of different type covering cyclization: 1----CH=, 2----CH=--(ring), 3----CHaC--, 4----CH=C---~, 5---CH----.
Kinetics of intramoleeular eyclization of polyisoprene
1153
TABLE 4. KINETIC CHARACTERISTICSOF THE STEADY-STATE PERIOD OF CYCLIZATIOlq
k¢
7~
60°; 0 10 20
kt
kt
[P~0~]--7"5%
140°; [P,O6]--7"5% 0.6
0 0.25 0.5
95 61g 26.4
96~g 16g 0 _ 4 6 . 5 31.7 0"50 48.5 31.7 100°; [P~05]-- 7-5%
0.4
0 1.0 2.0
95 62.6 16.4
9 4 5 6 . 29.3 2055.
0.6
0 0.25 0.5
95 45 g 13.6
9656"50 13-1 21.0 42-4
--3"7 2.12
0-03
0 g --137 80 1"31 0.6 16 4O 140°; [P,Os]-- 3"7%
80°; [P,05]--7.5%
0 0.5 1.0 0 0"5 1.0
7 28-1
0.61
39.3 28.1
0 --39"3 22"1 0"35 0.6 21"1 44'3 140°; [P~06] -- 9.0% 204 g I--163 38.7
77.4
1.72 0.7
f
We have previously used the high-resolution NMR method for study of the cyclization of squalene [6]. In the present work the NMR method was used for study of the kinetics of eyclization of polyisoprene at 100 ° and a P20~ concentration of 7.5% by weight. A 2"0
1.0
I
0
I
#
I
I
I
I
8 12 Time, hn
K
I
16
FIG. 7. Variation in the average number of rings per block (A) during cyclization of SKI-3 at 100 °. Concentration of P205--7.5% b y weight. I
Figure 6 shows the kinetics of change in the relative intensity of the signal from protons of different type. The relative intensities were determined by the weight method. They are the ratios of the area of the signal from the given type of proton
to the total area of the spectrum.
The chemical shifts and the relative intensities of the signals are given in Table 5.
1154
I. A. T U T O R S K I I e$ aZ.
The average number of rings in a block was calculated from the intensities of various peaks, found experimentally, according t o the formula [8]:
n=(1-~)/(]~-a) where n is the average number of rings in a block, a=815, fl=817(Is-~I4), and 13, 14 and 15 are the relative intensities of the signals of protons of the types in (CHa)C--~, --CH2--C~-- and --CH---- respectively. The time dependence of the average number of rings in a block is shown in Fig. 7. I t is seen that the results are in good agreement with the calculated values of n obtained from the results of infrared spectroscopy and chemical analysis, and with the values of ]cc/kt obtained from the kinetic calculations. Hence in the early stages of the reaction monocyclic structures are formed, the double bonds of which are reactivated and form bi- and polycyclic structures. On the basis of this evidence the cyelization process can be represented as follows: ~CH2
CH8
~CH~
Y .C
/
CH8
Y+ .¢
C H, ~CH2
CH2~
/
./o./
CHs
cycllzation
C CH3 H2
~ C H 2 CHs
CHs
CH~
CHs
CH,--CH,--C =CH = C H ~
H~C/QCH / H~
+
\7\
H,C~CH termination
C CH8 H~
H,
o~ ~
_~
C
+]t@
H ~ C H I CH8
c C /\~/\ H~C C CH~ II~C
C
\/I
C
\//~
C CHsC CHs CII~
Kinetics of intraznoleeular cyclization of polyisoprene
1155
T A B I ~ 5. CHEMICAL SHIFTS AND RELATIVE INTENSITIES OF THE SIGNALS OF THE PRODUCTS OF CYCLIZATION OF SKI-3 Chemical
Type of proton
CH 2-
--CH 2 - (ring) --(CH3)C = --CH~--C = CH = ~ linear / ring
shift, p.p.m. 0"9 1"26 1'66 2"0 5'1 5'25
Intensity
symbol
Mean relative intensity at cyelization times of (vain) 35
110
140
155
245
305
365
0-174 0-303 0"233 0.273
0'187 0'277 0"250 0"265
0'217 0'327 0"208 0.224
0'207 0"318 0'204 0'250
0"214 0'365 0"175 0"238
485 I 845
I~
0'0386 0"094 ! 0"191 0'0457 0"1095 0"234 0'366 0"330 0'216 0"0480 0"410 0"334
I~
0-0682 0"0463 0"0248 0-0178 0"0207 0"028 0"0206 0"0226 0"0125 0"0194
11 I2 12
0"202 0"358 0"175 0'243
! 0'238 0"348 0.171 1o.224
CONCLUSIONS
(1) The cyclization of polyisoprene in solution, catalysed by the P205-phenol :system, is a reaction of the first order in the initiation stage. The apparent energy o f activation for cyclization in the initiation stage is ~ 5.2 kcal/mole and the rate constant is directly proportional to the catalyst concentration. (2) The ratio of the rate constant of cyclization to the termination rate constant and the product of the initiation rate constant and the concentration of hydrogen ions can be found by solution of the set of differential equations describing the separate stages of the cyclization process. (3) The time dependence of the intensity of the high-resolution NMR signals from protons of different types in the cyclized rubber has been studied, and the number of rings in a block has been determined. The latter increases as the t i m e of cyclization increases. (4) The number of rings in a block, found by infrared spectroscopic analysis, chemical analysis, high-resolution NMR spectroscopy and from kinetic calculations indicates that monocyclic structures are formed in the initial stage of cyclization, and this is followed by formation of bi- and polycyclic structures. Translated by E . O.
PHILLIPS
REFERENCES l . D. F . L E E , J. S C A N L A N a n d W . F . W A T S O N , P r o c . R o y . Soc. A 2 7 3 : 345, 1963; R u b b e r C h e m . T e c h n o l . 36: 1005, 1963 2. J. K O S S L E R , J. V O D E H N A L , M. S T O L K A , J . K A L A L a n d E. H A R T L O V A , J . P o l y m e r Sci. C16: 1311, 1967 :3. A . N . L Y U B I M O V , I. Z . B E L I T S K I I , I. Y~. S L O N I M , A . F . V A R E N I K a n d V. I. F E D O R D V , Z a v o d . l a b . 32: 1163, 1966 4 . I. A . T U T O R S K I I , E . G. B O I K A C H E V A , G. S. P O L ' S M A N , A . N. S H A B O D A S H a n d B. A . D O G A D K I N , V y s o k o m o l . s o y e d . 7: 1394, 1965 ( T r a n s l a t e d i n P o l y m e r Sci. U . S . S . R . 7: 8, 1545, 1965) 5. V. R . A L I S H O Y E V , V. G. B E R E Z K I N , L. V. S I T N I K O V , A . I. T A L A L A Y E V , I. A . T U T O R S K I I , Z. P . M A R K O V I C H , V. S. T A T A R I N S K I I a n d E . G. B O I K A C H E V A , V y s o k o m o l . s o y e d . B I 0 : 432, 19 68 ( N o t t r a n s l a t e d i n P o l y m e r Sci. U . S . S . R . )
1156
M . G . CHAUSERet al.
6. I. A. TUTORSKII, I. Ya. SLONIM, E. G. BOIKACHEVA, O. A. MOCHALOVA, L. V, SOKOLOVA and B. A. DOGADKIN, Vysokomol. soyed. A10: 592, 1968 (Translated in Polymer Sei. U.S.S.R. 10: 3, 692, 1968) 7. B. P. DEMIDOVICH and I. A. MARON, Osnovy vyehislitel'noi matematiki (Principles of Computer Mathematics). p. 573, Izd. GIFML, 1960 8. A. KOL'TSOV, Vysokomol. soyed. Bg: 97, 1967 (Not translated in Polymer Sci. U.S.S.R.)
CHEMICAL MODIFICATION OF POLYMERS B A S E D ON D I P H E N Y L B U T A D I Y N E * i~I. G. CHAUSER,I. D. KALIKHMAN,M. I. CHERKASHII~and A. A. BERLIN Chemical Physics Institute, U.S.S.R. Academy of Sciences (Received 10 February 1969)
THE chemical modification of polymers, which is an important field of contemporary polymer chemistry, gives rise to the possibility of changing the properties of polymers in a directed manner, and enables definite conclusions to be drawn about the structure and reactivity of the starting substances. Extremely little attention has, however, been paid to the investigation of chemical transformations in polymers with a conjugated system. We attempted to follow two aims in studying the hydrogenation, bromination and nitration of polydiphenylbutadiynes: on the one hand, the products of the chemical modification were of interest as the starting substances for the synthesis of ph6tosensitive semi-conducting materials , and on the other hand, we expected to obtain additional information about the structure and properties of polyconjugated systems based on diphenylbutadiyne. It is the latter which is the subject of the present communication. EXPERIMENTAL The thermal a n d catalytic polymerization of the starting polydiphenylbutadiynes has been described previously [1]. Hydrogenation of the polymers was carried out in a rotating autoclave with a capacity of 0"5 1. 300 ml of deealin, 2 g of polymer and 5-10 g of the catalyst suspension (Raney nickel) were charged into the autoclave, the autoclave was purged with hydrogen to remove air and the pressure was raised to 100-135 arm at 140-150°C. During the reaction, which lasted 30 hr, a fresh portion of catalyst was added once. The catalyst was filtered off and washed with benzene, after which the solvent was distilled off from the filtrate in vacuo a n d the dry residue was precipitated from benzene in methanol. * Vysokomol. soyed. AI2: No. 5, I022-I028, 1970.
1145
(3) A radical mechanism of vulcanization of elastomers in the presence of the complexes is proposed, whereby as a result of addition of the complex to the rubber and the occurrence of polymerization, polyfunctional crosslinkages are formed, linking the rubber molecules by both covalent and coordinate bonds. Translated by E. O. PHILLIPS REFERENCES 1. A. A. DONTSOV, G. K. LOBACHEVA and B. A. DOGADKIN, K a u c h u k i rezina, No. 2, 19, 1968 2. B. A. DOGADKIN, A. A. DONTSOV and G. K. LOBACHEVA, Rus. Pat. (Authors' Certificate), 215477, Byull. izobret., No. 13, 78, 1968 3. N. D. Zfl,KH~tROV, Novye t i p y sinteticheskikh k a u c h u k o v v oblasti ikh prakticheskogo ispol'zovaniya (New Types of Synthetic R u b b e r and their Fields of Practical Application). p. 104, TSBTI, Yaroslavl', 1962 4. A. A. DONTSOV, G. K. LOBACHEVA, A. A. PODZHUNAS, A. A. RYBAKOV and B. A. DOGADKIN, K a u c h u k i rezina, No. 11, 3, 1968 5. H. GROSSMAN, Ber. 37: 1225, 1904 6. A. A. DONTSOV, G. K. LOBACHEVA and B. A. DOGADKIN, Kolloid. zh. 29 : 445, 1967 7. S. M. GUBRELL, L. MIfLLINS a n d R. S. RIVLIN, Trans. F a r a d a y Soc. 49: 1495, 1953 8. L. M. KURACHENKOVA and A. G. SHVARTS, Vysokomol. soyed. B10: 104, 1968 (Not translated in Polymer Sci. U.S.S.R.) 9. A. A. DONTSOV, G. K. LOBACHEVA a n d B. A. DOGADgIN, Vysokomol. soyed. A l l : 2370, 1969 (Translated in P o l y m e r Sei. U.S.S.R. 11: 11, 2689, 1969) 10. A. D. DONTSOV, V. F. SOLDATOV, A. N. KAMENSKII and B. A. DOGADKIN, Kolloid. zh. 31: 370, 1969
THE KINETICS OF INTRAMOLECULAR CYCLIZATION OF POLYISOPRENE* I. A. TUTO~SKU, E. G. BOIKACHEVA, I. G. BUKA:gOV and B. A. DOGADKIN M. V. Lomonosov I n s t i t u t e of F i n e Chemical Technology, Moscow
(Received 24 January 1969)
As A RESULTof extensive use of the spectroscopic method of study of the structure of the products of eyclization of polyisoprene [1] and polybutadiene [2] it has become possible to determine such structural characteristics of cyclized rubbers as the type of double bonds present and the number of rings in a block. Study of the kinetics of change of these characteristics during the cyclization process * Vysokomol. soyed. A12: No. 5, 1013-1021, 1970.
1146
I . A . TUTORSKIIet al.
provides a d e e p e r u n d e r s t a n d i n g o f t h e m e c h a n i s m o f this complex reaction. T h e p u r p o s e o f t h e present work is to elucidate t h e kinetics o f cyclization o f polyisoprene c a t a l y s e d b y t h e p h o s p h o r u s p e n t o x i d e - p h e n o l system. EXPERIMENTA L
The cyclization of SKI-3 synthetic polyisoprene (molecular weight 126,000, content of c/a-double bonds 95 %) was studied in a 1 : 1 mixture ofxylene and phenol. The concentration of the polymer solution was 15.4% (2.205 mole/1.), the concentration of catalyst was varied between 3 and 9% of the weight of the rubber and the temperature was varied between 60 and 140°. The reaction was conducted in an atmosphere of dry carbon dioxide. The cyclized rubber in test samples of the solution was precipitated by methanol, redissolved in benzene, reprecipitated by methanol and dried in vacuo at 60°. The course of the reaction was followed by the variation in total unsaturation, determined by reaction with perbenzoic acid, and by the variation in the intensity of infrared absorption bands and of the peaks of high-resolution NMR spectra. The infrared spectra were recorded in the 500-3100 cm -1 region in a UR-10 do~blebeam spectrograph. The specimens were prepared by compressing the cyclized rubber between pieces of copper foil at 120° and a pressure of 150 arm, then removing the foil by etching with a 10% solution of ammonium persulphate. This produced films of the polymer of thickness 20-30/~, framed by copper foil. The band at 1378 cm -1 (symmetrical deformation vibrations of C--H in thei~C--CH s _ group) was used as an internal reference. The mean square error in determinat on of the relative intensity of the relative optical density of the 840 cm -1 band was 5-7%. The high-resolution 17MR spectra were recorded in the radiospectrometer of the Central Automation Laboratory (CAL) (60 MHz) [3]. The solvent was CC14and the internal reference was hexamethylsiloxane. The concentration of polymer in the solution was varied between 4 and 7%, depending on the viscosity of the solution, and the spectra were recorded at 90 ° RESULTS AND DISCUSSION
I t was shown in reference [4] t h a t d u r i n g the course o f cyclization the conc e n t r a t i o n o f c i s - l , 4 double bonds in linear segments decreases, double bonds in rings a p p e a r a n d individual c o m p o n e n t s o f t h e c a t a l y s t s y s t e m and solvent (for example, phenol) a d d to t h e polymer. F i g u r e l a shows t h e kinetics o f d i s a p p e a r a n c e o f cis-l,4 double bonds during cyclization o f SKI-3, d e t e r m i n e d b y infrared spectroscopy. I t is seen t h a t w i t h i n the studied t e m p e r a t u r e range t h e r a t e o f the r e a c t i o n leading to disappearance o f linear double bonds increases s h a r p l y w i t h increase in t e m p e r a t u r e . F i g u r e lb shows t h e kinetics o f f o r m a t i o n o f ring double bonds. Since b y d e p r o t o n i z a t i o n a double b o n d can be f o r m e d in one o f t h r e e positions: ~ '
~//~x~ °r ~
'
the n u m b e r of ring double bonds was calculated as the difference b e t w e e n t h e t o t a l d o u b l e - b o n d content, d e t e r m i n e d w i t h perbenzoic acid, a n d t h e c o n t e n t o f linear double bonds d e t e r m i n e d b y m e a n s o f t h e 840 cm -1 b a n d in the infrared s p e c t r u m . T h e calculated results are given in T a b l e 1.
Kinetics of intramolecular cyclization of polyisoprene
1147
In the initial stage of the reaction (up to 30 rain) (Fig. lb) the rate of formation of ring double bonds increases with increase in temperature, b u t at a high degree of cyelization and at high temperatures (100 and 140 °) the limiting quantity of /7£~%
80
80
:\ n~,%l
o
[]
b
= 2
40
#
0
I
#
8
i
Time, hp.
"
i
12
I
I
16
I
I 20
FIG. 1. Variation in the number of linear ci#.l,4 (a) and ring (b) double bonds during eyclization. Concentration of P205--7"5% by weight. 1--60°; 2--80 °, 3-100°, 4--140°; n+, is the percentage of linear and nR of ring double bonds. ring double bonds being formed begins to decrease. This indicates that the double bonds in monocyclic units become reactivated, forming the bi- and polycyclic structures that we have discussed previously [4]. Figure 2 shows the kinetics of disappearance of cis-l,4 double bonds during cyclization at 140 ° with different concentrations of catalyst. The rate of disappearance of linear double bonds increases as the concentration of catalyst is increased. Figure 3 shows the kinetics of change in the relative intensity of the 750 cm -I band, corresponding to phenol combined in the ortho-position. Both the rate of addition of phenol and the limiting quantity added increase with increase in temperature. The order of reaction in the initial stage of cyclization under various experimental conditions was determined b y the differential method, using the equation w = # . c n, where w is the reaction rate, k the rate constant, c the concentration of double bonds and n the order of reaction.
1148
I. A. TUTORSKII et aL T~LBLE 1. K n ~ T I C S Or CYCLIZATION OF POLYISOPRENE
T i m e o f cyclization, hr
ConcentraConcentration of [ Number of tion of • ing d o u b l e rings, linear double n b o n d s [L], % b o n d s [R], %
%
140°; [PaOs]--7-5 w t . 0.5 1.0 2.0 3.0 12.0
26"4 10.2 2.0 1-8
40"0 44-8 45"2 40"7 31"0
0.8 I-0 1.2 1.4 2.2
lOOO;[P,0~]-7.5 wt.% 0.5 1.0 2-0 3.0 4.0 5.0 13.0
46"2 39.3 16"4 8"8 8"0 7'2
29.3 28.1 40.1 38.2 36.2 30-0 27.8
0.8 1.2 1.1 1.4 1-5 2.1 2.6
80°; [ P 2 0 5 ] - - 7 " 5 w t . % 1.0 2.0 3.0 5.0 7.0 10-0 14-0 18.0 26.0
48"5 27"0 17"9 5-3 2-6 1"5 2.6 2"3 1.3
31.7 47.6 49"9 49"3 54"4 49-3 45.2 46"0 44-6
0.6 0.5 0.6 0.9 0.8 1.0 1.2 1.1 1.2
60°; [P~05] -- 7"5 w t . % 15"0 20"0 30"0
45"1 21-0 18.5
24"7 42.4 41.9
1.2 0.9 0.9
140°; [P~O5]--3-7 w t . % 1.0 1.5 2.0 3.0 4.0 11.0
62.6 29"8 16"4 9"1 1"5
21.1 42.2 44"3 46.1 50.2 46.3
0.3 0.7 0"9 1.0 1.0 1.2
140°; [PzOa]--9"O w t . % 0-5 1.0 12.0
13.6 4.8 --
38-7 42.8 30.7
1-2 1.2 2.3
Kinetics of intramolecular cyclization of polyisoprene
1149
The dependence of the initial rate of cyclization on the initial concentration of double bonds is represented by a straight line when plotted as log (zlc]At) against log c (Fig. 4). The slope of this line gives the order of reaction. n~,% fO0 80 60 40 20
0
4
8 Time , hp
12
FIG. 2. Variation in the content of linear c/s-l,4 double bonds during cyclization at 140 °. Concentration of P~05, % b y weight: 1--9.0, 2--7.5, 3--3.7.
Calculated values of the order of the initiation reaction are given in Table 2 for various reaction conditions, from which it is seen that these values are close to unity. I)75o/D,378 I
•
..K--.
x
0
I
2
I
I
I
.I
fO
8
i
I
!
14
I
/8
T i m e , hn FIG. 3. Variation in the relative optical density of the 750 em -1 b a n d (phenol combined in the o-position) during cyclization. Temperature, °C: 1-3--140, 4--100,
5--80. Concentration of P=Os, % by weight: •--9.0, 2, 4, 5--7.5, 3--3-7. The rate constants were calculated from the first order equation. These values are given in Table 3. The initiation rate constant is directly proportional to the catalyst concentration (Fig. 5a). The apparent energy of activation for cyclization, found graphically from the Arrhenius equation,is N 5.2 kcal/mole (Fig. 5b). This is in satisfactory agreement with the value 7 keal/mole found by pyrolytic gas chromatography [5].
1150
I. A. TUTORSXII et al.
The cyclization of diene polymers can be divided into the stages of initiation (formation of active centres), cyclization (propagation), deprotonization (chain termination) and re-initiation (activation of the ring double bonds formed) [1, 6]. According to this the cyclization process can be described by the set of differential equations: d~]---- b~[L] [H +]q-be[He +]
(1)
d [HC+] - - b,[L] [H+] +bIH +] [C]--k,[HC +]
(2)
dt
d [C] dt =--k'[H+] [C] +kt[HC +]
(3)
where [L] and [C] are the concentrations of linear and rings double bonds respectively, k~ is the initiation rate constant, k2 the rate constant of re-initiation, ks the rate constant of cyclization and k t the termination rate constant. TABLE 2. CALCULATED VALUES OF THE ORDER OF THE INITIATION REACTIOI~ !
Temperature Catalyst concen)f e y c l i z a t i o n , t r a t i o n (mole/mole o f S K I - 3 ) × 10 -~ °C
Order of Temperature Catalyst concenr e a c t i o n , o f cyclization, t r a t i o n (mole/mole n o f S K I - 3 ) x 10 -~ °C
3"59 3"59 3.59
60 80 100
1.15 1"05 0"985
I
140 140 140
3.59 1.78 4.24
Order of reaction, n 0.936 1.10 [ 0.96
For the steady-state period of cyclization we can assume that d [HC+]/dt=O. Then from equation (2) we obtain: [ H e +] =
b.,[H÷] [L] +kiH +] [13]
(4)
After substitution of (4) in (1) and (2) we obtain: _ _ _[L]=bl[H+ d ] [L ] + ~b~ (bill+ ] [L] +b2[H+] [(3])
(5)
= - - k , [ H +] [C] +b~[H +] [L] +k,[H +] [C]= k~[H+] [L].
(6)
dt
die/
dt
Assum~ug that bl----k2 we obtain:
ddt[L]__bx[H+][L] + ~ (bl[H+] [L]--k~[H+] [C])*
(7)
• T h e e x p r e s s i o n o b t a i n e d for c y c l i z a t i o n o f p o l y b u t a d i e n e in ref. [2] h a s a d i f f e r e n t f o r m b e c a u s e t h e a u t h o r s m a d e a n e r r o r i n its d e r i v a t i o n .
Kinetics of intraanolecular eyelization of polyisoprcne
1151
W e f o u n d kc/k t a n d kl[H +] f r o m expressions (6) and (7). Differentiation was carried o u t according to t h e formula: 1 Y~=~-h (--Yo+Y~) where Y0, Yl a n d y~ are t h e values o f t h e functions at e q u i d i s t a n t points [7].
TABLE 3.DETERMINATIONOF C Y C L I Z A T I O I N 7
:RATE COI~STAlffTS
Temperature (Moles P,O,/ Ik 2 X 3 log[A.]ITemperatur. (MolesP2OJ/k of cycliza/mole of ~ = tion, °C SKI-3) × 10-3/ 140 100 80 60
3.59 3.59 3.59 3.59
2×31o [A0] t [-~1]' of cycliza/mole of / = ~ g[A~]' rain -1 tion, °C SKI-3) × 10-2/ rain -~
0.0133 0.00932 0.0043 0-00287
140 140 140
0.00361 0.0133 0.0169
1.78
3.59 4.24
The ratios o f the cyclization r a t e c o n s t a n t to the t e r m i n a t i o n r a t e c o n s t a n t a n d t h e p r o d u c t s o f t h e i n i t i a t i o n r a t e c o n s t a n t (kc/kt) a n d the h y d r o g e n - i o n c o n c e n t r a t i o n (kl[H+]) for various conditions o f cyclization are given in Table 4.
lo 9 c , 10-2, m o l e l l .
0
8
I
I
I
16 I
2¢
I
I
I
I
32 I
-2.0 f~
-2.2-
n
•
•
,
0
o
X
-2"¢
C/o
/o
FIG. 4. Determination of the order of reaction' in the cyclization of polyisoprene. Temperature, °C: 1, 4, 5--140, 2--100, 3--80. Concentration of P205, °/o by weight: 1-3--7.5, 4--3.7, 5--9.0. T h e p r o d u c t k l [ i +] increases as the t e m p e r a t u r e a n d c a t a l y s t c o n c e n t r a t i o n are increased. No clear effect o f t e m p e r a t u r e on t h e ratio o f t h e cyclization r a t e
1152
I. A. TuToRsxII et at.
c o n s t a n t to t h e t e r m i n a t i o n r a t e c o n s t a n t is seen because o f t h e short d u r a t i o n o f t h e s t e a d y - s t a t e period. This ratio remains c o n s t a n t w h e n t h e c a t a l y s t concentrat i o n is increased. k,fO'~,rnZn'1 2.4
2.8
I
1.8f
a
3
3.0 I/'T,~O-3
I
I
b
logk
-2"0
1.#
2.8
I
30
-2"2
,.of
-2.#
O'2 .01
I
i I O'O3 molo P2Os/molo 8/
I
-2.6
O'O5
FIG. 5. Dependence of the initial rate constant on catalyst concentration at 140° (a) and on temperature (b). a-- Concentration of P=O5 (mole/mole of SKI-3): 1--1.78 × × 10-2, 2--3.59× 10-% 3--4.24× 10-=; b--~emperature, °C: •--60, 2--80, 3--100, 4-- 140. Concentration of P=O6--7"5~o by weight. The r a t i o kc//ct defines the n u m b e r o f rings in a cyclic block a n d in the e a r l y stages o f cyclization it agrees satisfactorily with t h e value o f n (Table 1). These values indicate t h e f o r m a t i o n o f monocyclic s t r u c t u r e s in t h e initial stage o f cyclization, w i t h a later change t o hi- a n d polycyclic structures. _7_" 0"5
D
0"3 0"2
~.~
v 3
0"1 " I
2
J
#
5
6
'I
5" /2
1#
Time, hr,
FIG. 6. Variation in the relative intensity of NMR peaks from protons of different type covering cyclization: 1----CH=, 2----CH=--(ring), 3----CHaC--, 4----CH=C---~, 5---CH----.
Kinetics of intramoleeular eyclization of polyisoprene
1153
TABLE 4. KINETIC CHARACTERISTICSOF THE STEADY-STATE PERIOD OF CYCLIZATIOlq
k¢
7~
60°; 0 10 20
kt
kt
[P~0~]--7"5%
140°; [P,O6]--7"5% 0.6
0 0.25 0.5
95 61g 26.4
96~g 16g 0 _ 4 6 . 5 31.7 0"50 48.5 31.7 100°; [P~05]-- 7-5%
0.4
0 1.0 2.0
95 62.6 16.4
9 4 5 6 . 29.3 2055.
0.6
0 0.25 0.5
95 45 g 13.6
9656"50 13-1 21.0 42-4
--3"7 2.12
0-03
0 g --137 80 1"31 0.6 16 4O 140°; [P,Os]-- 3"7%
80°; [P,05]--7.5%
0 0.5 1.0 0 0"5 1.0
7 28-1
0.61
39.3 28.1
0 --39"3 22"1 0"35 0.6 21"1 44'3 140°; [P~06] -- 9.0% 204 g I--163 38.7
77.4
1.72 0.7
f
We have previously used the high-resolution NMR method for study of the cyclization of squalene [6]. In the present work the NMR method was used for study of the kinetics of eyclization of polyisoprene at 100 ° and a P20~ concentration of 7.5% by weight. A 2"0
1.0
I
0
I
#
I
I
I
I
8 12 Time, hn
K
I
16
FIG. 7. Variation in the average number of rings per block (A) during cyclization of SKI-3 at 100 °. Concentration of P205--7.5% b y weight. I
Figure 6 shows the kinetics of change in the relative intensity of the signal from protons of different type. The relative intensities were determined by the weight method. They are the ratios of the area of the signal from the given type of proton
to the total area of the spectrum.
The chemical shifts and the relative intensities of the signals are given in Table 5.
1154
I. A. T U T O R S K I I e$ aZ.
The average number of rings in a block was calculated from the intensities of various peaks, found experimentally, according t o the formula [8]:
n=(1-~)/(]~-a) where n is the average number of rings in a block, a=815, fl=817(Is-~I4), and 13, 14 and 15 are the relative intensities of the signals of protons of the types in (CHa)C--~, --CH2--C~-- and --CH---- respectively. The time dependence of the average number of rings in a block is shown in Fig. 7. I t is seen that the results are in good agreement with the calculated values of n obtained from the results of infrared spectroscopy and chemical analysis, and with the values of ]cc/kt obtained from the kinetic calculations. Hence in the early stages of the reaction monocyclic structures are formed, the double bonds of which are reactivated and form bi- and polycyclic structures. On the basis of this evidence the cyelization process can be represented as follows: ~CH2
CH8
~CH~
Y .C
/
CH8
Y+ .¢
C H, ~CH2
CH2~
/
./o./
CHs
cycllzation
C CH3 H2
~ C H 2 CHs
CHs
CH~
CHs
CH,--CH,--C =CH = C H ~
H~C/QCH / H~
+
\7\
H,C~CH termination
C CH8 H~
H,
o~ ~
_~
C
+]t@
H ~ C H I CH8
c C /\~/\ H~C C CH~ II~C
C
\/I
C
\//~
C CHsC CHs CII~
Kinetics of intraznoleeular cyclization of polyisoprene
1155
T A B I ~ 5. CHEMICAL SHIFTS AND RELATIVE INTENSITIES OF THE SIGNALS OF THE PRODUCTS OF CYCLIZATION OF SKI-3 Chemical
Type of proton
CH 2-
--CH 2 - (ring) --(CH3)C = --CH~--C = CH = ~ linear / ring
shift, p.p.m. 0"9 1"26 1'66 2"0 5'1 5'25
Intensity
symbol
Mean relative intensity at cyelization times of (vain) 35
110
140
155
245
305
365
0-174 0-303 0"233 0.273
0'187 0'277 0"250 0"265
0'217 0'327 0"208 0.224
0'207 0"318 0'204 0'250
0"214 0'365 0"175 0"238
485 I 845
I~
0'0386 0"094 ! 0"191 0'0457 0"1095 0"234 0'366 0"330 0'216 0"0480 0"410 0"334
I~
0-0682 0"0463 0"0248 0-0178 0"0207 0"028 0"0206 0"0226 0"0125 0"0194
11 I2 12
0"202 0"358 0"175 0'243
! 0'238 0"348 0.171 1o.224
CONCLUSIONS
(1) The cyclization of polyisoprene in solution, catalysed by the P205-phenol :system, is a reaction of the first order in the initiation stage. The apparent energy o f activation for cyclization in the initiation stage is ~ 5.2 kcal/mole and the rate constant is directly proportional to the catalyst concentration. (2) The ratio of the rate constant of cyclization to the termination rate constant and the product of the initiation rate constant and the concentration of hydrogen ions can be found by solution of the set of differential equations describing the separate stages of the cyclization process. (3) The time dependence of the intensity of the high-resolution NMR signals from protons of different types in the cyclized rubber has been studied, and the number of rings in a block has been determined. The latter increases as the t i m e of cyclization increases. (4) The number of rings in a block, found by infrared spectroscopic analysis, chemical analysis, high-resolution NMR spectroscopy and from kinetic calculations indicates that monocyclic structures are formed in the initial stage of cyclization, and this is followed by formation of bi- and polycyclic structures. Translated by E . O.
PHILLIPS
REFERENCES l . D. F . L E E , J. S C A N L A N a n d W . F . W A T S O N , P r o c . R o y . Soc. A 2 7 3 : 345, 1963; R u b b e r C h e m . T e c h n o l . 36: 1005, 1963 2. J. K O S S L E R , J. V O D E H N A L , M. S T O L K A , J . K A L A L a n d E. H A R T L O V A , J . P o l y m e r Sci. C16: 1311, 1967 :3. A . N . L Y U B I M O V , I. Z . B E L I T S K I I , I. Y~. S L O N I M , A . F . V A R E N I K a n d V. I. F E D O R D V , Z a v o d . l a b . 32: 1163, 1966 4 . I. A . T U T O R S K I I , E . G. B O I K A C H E V A , G. S. P O L ' S M A N , A . N. S H A B O D A S H a n d B. A . D O G A D K I N , V y s o k o m o l . s o y e d . 7: 1394, 1965 ( T r a n s l a t e d i n P o l y m e r Sci. U . S . S . R . 7: 8, 1545, 1965) 5. V. R . A L I S H O Y E V , V. G. B E R E Z K I N , L. V. S I T N I K O V , A . I. T A L A L A Y E V , I. A . T U T O R S K I I , Z. P . M A R K O V I C H , V. S. T A T A R I N S K I I a n d E . G. B O I K A C H E V A , V y s o k o m o l . s o y e d . B I 0 : 432, 19 68 ( N o t t r a n s l a t e d i n P o l y m e r Sci. U . S . S . R . )
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6. I. A. TUTORSKII, I. Ya. SLONIM, E. G. BOIKACHEVA, O. A. MOCHALOVA, L. V, SOKOLOVA and B. A. DOGADKIN, Vysokomol. soyed. A10: 592, 1968 (Translated in Polymer Sei. U.S.S.R. 10: 3, 692, 1968) 7. B. P. DEMIDOVICH and I. A. MARON, Osnovy vyehislitel'noi matematiki (Principles of Computer Mathematics). p. 573, Izd. GIFML, 1960 8. A. KOL'TSOV, Vysokomol. soyed. Bg: 97, 1967 (Not translated in Polymer Sci. U.S.S.R.)
CHEMICAL MODIFICATION OF POLYMERS B A S E D ON D I P H E N Y L B U T A D I Y N E * i~I. G. CHAUSER,I. D. KALIKHMAN,M. I. CHERKASHII~and A. A. BERLIN Chemical Physics Institute, U.S.S.R. Academy of Sciences (Received 10 February 1969)
THE chemical modification of polymers, which is an important field of contemporary polymer chemistry, gives rise to the possibility of changing the properties of polymers in a directed manner, and enables definite conclusions to be drawn about the structure and reactivity of the starting substances. Extremely little attention has, however, been paid to the investigation of chemical transformations in polymers with a conjugated system. We attempted to follow two aims in studying the hydrogenation, bromination and nitration of polydiphenylbutadiynes: on the one hand, the products of the chemical modification were of interest as the starting substances for the synthesis of ph6tosensitive semi-conducting materials , and on the other hand, we expected to obtain additional information about the structure and properties of polyconjugated systems based on diphenylbutadiyne. It is the latter which is the subject of the present communication. EXPERIMENTAL The thermal a n d catalytic polymerization of the starting polydiphenylbutadiynes has been described previously [1]. Hydrogenation of the polymers was carried out in a rotating autoclave with a capacity of 0"5 1. 300 ml of deealin, 2 g of polymer and 5-10 g of the catalyst suspension (Raney nickel) were charged into the autoclave, the autoclave was purged with hydrogen to remove air and the pressure was raised to 100-135 arm at 140-150°C. During the reaction, which lasted 30 hr, a fresh portion of catalyst was added once. The catalyst was filtered off and washed with benzene, after which the solvent was distilled off from the filtrate in vacuo a n d the dry residue was precipitated from benzene in methanol. * Vysokomol. soyed. AI2: No. 5, I022-I028, 1970.