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Spectroscopic determination of the content of trans and cis units in polypentenamere
SPECTROSCOPIC DETERMINATION OF THE CONTENT OF TRANS AND CIS UNITS IN POLYPENTENAMERE* A. P . KOROBKO, V. S. TUROV a n d V. M. CHEREDNICHElgKO L. Ya. Karpov Scientific Research Institute of Physical Chemistry (Received 8 January
1974)
A description is given of a method for determining molar coefficients of extinction of absorption bands at 967 cm -1 (trans units) and 1404 cm -1 (c/s units) in polypentenamere. The molar coefficient of extinction of the b a n d at 967 cm -~ was determined in CS2 and CC14. The possibility is considered of using CC14 for the quantitative determination of t r a n s units in polypentenamere. THE POSSIBILITY of using I R spectroscopy for the quantitative determination of t/tans and e/s units in p o l y a l k e n a m e r s - - a new class of flexible-chain synthetic polymers--is examined [1]. A description is given in this paper of the quantitative determination of t r a n s and e~ units in polypentenamere (PPlYl) from solutions in CC14. Analysis was carried out using the molar coefficients of extinction of bands related to vibrations of t r a n s and cis units; a new method of determination is described. The molar coefficient of extinction of the band of t r a n s units was also measured in carbon disulphide. TABLE 1. C H A R A C T E R I S T I C S OF ~ P P l ~ SAMPLES
Sample, No.
1 2 3 4 5 6 7
Main contents of units
TransTransTrans-cis Trans-cis Ci8CisTrans -
References
Overall content units,of %unsaturated chemical I I analysis i
t
i
[2] [2] [3]
98-2 99-0 97-7
[3] [4]
98.o
[4]
97.4
[2]
99.0
NMR
! average ! value 98.2 97.5 97.7 98.2 95.0
--
96.0 -98"4 95"0 --
97"0
i
[0] dl/g (25 °, toluene) 5.45 2.52 6.10 6-40 3.10
97 '4
1.10
98.0
3.90
For the measurements we synthesized samples with different contents of t r a n s and c/s units using well known catalytic systems [2-4]. Characteristics of samples are shown in Table 1. The overall n u m b e r of u n s a t u r a t e d units was determined chemically [5] and by NMR [1]; results showed satisfactory agreement. The samples were free from catalyst residues (ashes). * Vysokomol. soyed. A17: No. 1, 195-198, 1975. 229
230
A. 1). KOROBKO et al.
lI~ spectra were recorded in t h e range of 900-1100 a n d 1300-1600 c m -1 using a U R - 1 0 s p e c t r o p h o t o m e t e r with a NaC1 p r i s m according to t h e ' f o u r t h slit p r o g r a m m e ' . B a n d s a t 967 (trans units) a n d 1404 e m -1 (c/s units) were t h e a n a l y t i c a l bands. I t s h o u l d be n o t e d t h a t t h e m a x i m u m of t h e b a n d of t r a n s u n i t s in CCI~ is displaced b y a b o u t 2 c m -1 t o t h e region of higher frequencies. Sectional cells w i t h NaC1 openings [6] 0.01 and 0-05 cm t h i c k were used for a trans b a n d (mainly 0.01 cm for solutions in CC14) a n d 0.05 a n d 0.2 c m for a c/s band. T h e c o n c e n t r a t i o n of solutions was 0.15-0-75 mole/1. T h e a b s o r p t i o n of solvents was c o m p e n s a t e d b y a well k n o w n m e t h o d . T h e q u a l i t y of c o m p e n s a t i o n was e x a m i n e d in every
case.
°
2O 0
1 l,f
I
1 YO
__
/~ ,
lO-Z,Cr/7"!
.
! Y
I R s p e c t r u m of P P M (sample 4) in CC14 solution of initial c o n c e n t r a t i o n 0.35 mole/1. To record t h e b a n d of c/s u n i t s a t 1404 cm -1 a cell 0-203 cm in thickness a n d for a b a n d of t r a n s u n i t s a t 967 cm -1, a cell 0-013 cm in thickness was used. The base line of t h e b a n d of t r a n s units was s i t u a t e d b e t w e e n frequencies a t 920 a n d 1005 cm -~, as shown by t h e Figure. F o r a b a n d of v/s s t r u c t u r e s t h e base line m a y be d r a w n b y two m e t h o d s . W i t h t h e first m e t h o d a b s o r p t i o n b e t w e e n frequencies a t 1390 a n d 1415 cm -1 was considered (continuous line in t h e Figure). W i t h t h e second m e t h o d a b s o r p t i o n was Considered a t t h e m a x i m u m point, c o u n t i n g from t h e b r o k e n base line [1]. To calculate m o l a r coefficients of e x t i n c t i o n of b a n d s of t r a n s a n d c/s units t h e prop o r t i o n of s a t u r a t e d u n i t s was excluded f r o m t h e initial c o n c e n t r a t i o n of solutions. T h e optical densities of a n a l y t i c a l bands Dt a n d Do m e a s u r e d were divided b y t h e overall conc e n t r a t i o n of u n s a t u r a t e d units ct~cc (mole/l.) a n d t h e thickness of t h e absorbing layer d Dt De (cm). Values of K t = and Kc--~-t h u s o b t a i n e d are given in Table 2. (~÷oo) d (ct+cc) d The same Table also shows t h e a r i t h m e t i c m e a n error of m e a s u r e m e n t o b t a i n e d from repeated measurements. R e s u l t s in Table 2 enable four linear equations to be derived of t h e t y p e K t - - B e + B ~ K e , in w h i c h c o n s t a n t s Be a n d B1 m a y be d e t e r m i n e d b y t h e m e t h o d of least squares [7, 8]. Calculations result in t h e following e q u a t i o n s of lines s i t u a t e d v e r y near the e x p e r i m e n t a l points: Kt(CS,)-- 138.86--16-85Kc~ (CC1,) Kt(CS~)-- 141.50-15.52Kc2 (CC1,) Kt(CC1,) -- 117.03-14.46Ke~(CC1,) Kt(CC1,) = 120.57-13.61Kc. (CC1,).
Spectroscopic determination of content of trans and cis units in polypentenamere
231
I t is evident t h a t with linear extrapolation of Kt values to zero values of Kc the relevant unknowll molar coefficients of extinction of the band of trans units et m a y be obtained and when K t ~ 0, the molar coefficients of extinction of the band of cis units ec (Table 3), derived. TABLE
2. V A L U E S OF K t A N D
Kc
OF P P M
SAMPLES I N SOLUTIOI~S I N C S z A N D C C I 4
W I T H T W O M E T H O D S OF D R A W I N G T H E BASE L I N E OF
T H E B A N D OF C ~ U N I T S
Values of Kt and Ke, mole -~ 1. cm -x Kcl (CCId), Kc2 (CC14), Kt(CC1,) first method second method
Sample, No. Kt(CS,)
121.04-3.0 100.44-2.0 77.04-1.1 55.04-1.2 36.14-0.7 12-14-0.2
92.74-2-5 64.04-2.O 48.74-1.5 16.44-0-5
1.104-0.04 1.304-0.02 2.604-0.02 4-204-0.10 5.704-0-06 7.264-0.05
1-424-0.04 1.604-0-01 3.034-0.06 4.804-0.10 6.304-0.10 7.954-0.10
As an example the result of analysing sample 7 (Table 1 ) in CCI~ solution m a y be given. Using coefficients e t ~ l l 7 and 8c~8.1 ct~83.7 and c ~ 1 4 . 0 ° / o were derived. The overall content of unsaturation is 97.7 ~/o which is in satisfactory agreement with the value obtained by N'MR and a chemical method. TABLE
3. M O L A R
COEFFICIENTS
OF E X T I N C T I O N OF B A N D S
OF
trans A N D ci8 U N I T S OF P P M
Using the base line of the cis band
Values of K t and K c, mole -l 1. cm -~ solutions in CS~ and CC1,
solutions in CC14
et (CS~)
e~ (CC14)
et (CC1,)
8c (CC14)
139 142
8.2 9-1
117 121
8.1 8.9
Results indicate t h a t for a full analysis of PP M samples solutions in CCI4 can only be used. I t is known t h a t in the 1000 cm -I region CC14 is subject to absorption, however, transmission is not less than 35~o with absorption layer thicknesses of up to 0-04 cm. U n d e r these conditions the outline of the band of the substance examined is not distorted [9]. This somewhat restricts the range of application of the analytical method described. However, practice indicates t h a t P P M with a limiting viscosity in toluene at 25 ° of up to 6-7 dl/g with a content of trans bonds of over 8-10~o , m a y be safely analysed in CC14 solutions. I n other words, the method can be u s e d to analyse most P P ~ used for practical purposes, which is v e r y significant if we bear in mind the lower toxicity and volatility of CCl~ compared with carbon disulphide. I t is fairly complicated [10] to evaluate the mean square deviation of experiment when both values (Kt and Kc) are measured with some inaccuracy. We therefore evaluated the errors involved by using the arithmetic mean error and calculating the band bounded by two lines. I t appeared t h a t the error of the extrapolated value of 8t is 4-2.5 of unity (in GC1,) and -b4.5 (in carbon disulphide) and ee-}-(0"l-0"15) of unity. This involves an error in determining trans bonds in :PPI~ of ~ 2.5% (from CC14) and ~ 3% (from carbon disulphide)
232
A . P . ~4~OROBKOet al.
a n d c6~ units, ~ 2%. The accuracy of these estimates is confirmed b y calculating the mean square deviation of et and the correlation coefficient between et and e¢ assuming that the error involved in measuring Ke m a y be ignored (Table 4). T~BLE
4. R O O T MEAN S Q U A R E E R R O R (•)
OF T H E
E X T R A P O L A T E D V A L U E S OF gt A N D C O E F F I C I E N T S OF C O R R E L A T I O N (p) B E T W E E N
Base line of the c/s b a n d 1 2
Solutions in CSs and CCI~
8 t A N D ~c
Solutions in CC14
o-
p
~-
p
4.3 3.7
--0.56 --0.59
2.2 1.9
--0.57 --0.59
The error of measuring K¢ should be considered according to a former study [10] a n d involves some increase in the mean square deviation of the value of ct. Finally, the authors wish to t h a n k L. N. Kurkovskaya and N. N. Shapet'ko for their help in carrying out NMR measurements. Translated by E. SE~ERE
REFERENCES 1. C. TOSSI, F. CIA_MPELLI and G. DALI.'ASTA, J. Polymer Sci. Polymer Phys. Ed. 11: 529, 1973 2. G. I~ATTA, (L DALL'ASTA and G. MAZZANTI, Angew. Chemie 76: 765, 1964 3. R. J. MI~CHAK and H. TUCKER, Polymer Preprints 13: 885, 1972 4. G-. D),I.L'ASTA and 6~. MOTRONI, Angew. Makromolek. Chem. 16/17: 51, 1971 5. T. S. LEE, I. M. KOLTHOFF and M. A. MAIRS, J. Polymer Sci. 3: 66, 1948 6. N. V. KOZLOVA, F. F. SIYKHOV and V. P. BAZOV, Zavodsk. lab. 31: 968, 1965 7. K. P. YAKOVLEV, Matematicheskaya obrabotka rezul'tatov izmerenii (Mathematical Analysis of Results of Measurements). GITL, 1950 8. I~. DREIPER a n d (L SMITH, Prikladnoi regressionnyi analiz (Applied Regression Analysis). Statistika, 1973 9. K. NAKANISI, Infrakrasnye spektry i stroyeniye organicheskikh soyedinenii (IR Spectra a n d Structure of Organic Compounds). Izd. "Mir", 1965 10. V. V. FEI)OROV, Teoriya optimal'nogo eksperimenta, (Theory of Optimum Experiment). Izd. "Nauka", 1971
1974)
A description is given of a method for determining molar coefficients of extinction of absorption bands at 967 cm -1 (trans units) and 1404 cm -1 (c/s units) in polypentenamere. The molar coefficient of extinction of the b a n d at 967 cm -~ was determined in CS2 and CC14. The possibility is considered of using CC14 for the quantitative determination of t r a n s units in polypentenamere. THE POSSIBILITY of using I R spectroscopy for the quantitative determination of t/tans and e/s units in p o l y a l k e n a m e r s - - a new class of flexible-chain synthetic polymers--is examined [1]. A description is given in this paper of the quantitative determination of t r a n s and e~ units in polypentenamere (PPlYl) from solutions in CC14. Analysis was carried out using the molar coefficients of extinction of bands related to vibrations of t r a n s and cis units; a new method of determination is described. The molar coefficient of extinction of the band of t r a n s units was also measured in carbon disulphide. TABLE 1. C H A R A C T E R I S T I C S OF ~ P P l ~ SAMPLES
Sample, No.
1 2 3 4 5 6 7
Main contents of units
TransTransTrans-cis Trans-cis Ci8CisTrans -
References
Overall content units,of %unsaturated chemical I I analysis i
t
i
[2] [2] [3]
98-2 99-0 97-7
[3] [4]
98.o
[4]
97.4
[2]
99.0
NMR
! average ! value 98.2 97.5 97.7 98.2 95.0
--
96.0 -98"4 95"0 --
97"0
i
[0] dl/g (25 °, toluene) 5.45 2.52 6.10 6-40 3.10
97 '4
1.10
98.0
3.90
For the measurements we synthesized samples with different contents of t r a n s and c/s units using well known catalytic systems [2-4]. Characteristics of samples are shown in Table 1. The overall n u m b e r of u n s a t u r a t e d units was determined chemically [5] and by NMR [1]; results showed satisfactory agreement. The samples were free from catalyst residues (ashes). * Vysokomol. soyed. A17: No. 1, 195-198, 1975. 229
230
A. 1). KOROBKO et al.
lI~ spectra were recorded in t h e range of 900-1100 a n d 1300-1600 c m -1 using a U R - 1 0 s p e c t r o p h o t o m e t e r with a NaC1 p r i s m according to t h e ' f o u r t h slit p r o g r a m m e ' . B a n d s a t 967 (trans units) a n d 1404 e m -1 (c/s units) were t h e a n a l y t i c a l bands. I t s h o u l d be n o t e d t h a t t h e m a x i m u m of t h e b a n d of t r a n s u n i t s in CCI~ is displaced b y a b o u t 2 c m -1 t o t h e region of higher frequencies. Sectional cells w i t h NaC1 openings [6] 0.01 and 0-05 cm t h i c k were used for a trans b a n d (mainly 0.01 cm for solutions in CC14) a n d 0.05 a n d 0.2 c m for a c/s band. T h e c o n c e n t r a t i o n of solutions was 0.15-0-75 mole/1. T h e a b s o r p t i o n of solvents was c o m p e n s a t e d b y a well k n o w n m e t h o d . T h e q u a l i t y of c o m p e n s a t i o n was e x a m i n e d in every
case.
°
2O 0
1 l,f
I
1 YO
__
/~ ,
lO-Z,Cr/7"!
.
! Y
I R s p e c t r u m of P P M (sample 4) in CC14 solution of initial c o n c e n t r a t i o n 0.35 mole/1. To record t h e b a n d of c/s u n i t s a t 1404 cm -1 a cell 0-203 cm in thickness a n d for a b a n d of t r a n s u n i t s a t 967 cm -1, a cell 0-013 cm in thickness was used. The base line of t h e b a n d of t r a n s units was s i t u a t e d b e t w e e n frequencies a t 920 a n d 1005 cm -~, as shown by t h e Figure. F o r a b a n d of v/s s t r u c t u r e s t h e base line m a y be d r a w n b y two m e t h o d s . W i t h t h e first m e t h o d a b s o r p t i o n b e t w e e n frequencies a t 1390 a n d 1415 cm -1 was considered (continuous line in t h e Figure). W i t h t h e second m e t h o d a b s o r p t i o n was Considered a t t h e m a x i m u m point, c o u n t i n g from t h e b r o k e n base line [1]. To calculate m o l a r coefficients of e x t i n c t i o n of b a n d s of t r a n s a n d c/s units t h e prop o r t i o n of s a t u r a t e d u n i t s was excluded f r o m t h e initial c o n c e n t r a t i o n of solutions. T h e optical densities of a n a l y t i c a l bands Dt a n d Do m e a s u r e d were divided b y t h e overall conc e n t r a t i o n of u n s a t u r a t e d units ct~cc (mole/l.) a n d t h e thickness of t h e absorbing layer d Dt De (cm). Values of K t = and Kc--~-t h u s o b t a i n e d are given in Table 2. (~÷oo) d (ct+cc) d The same Table also shows t h e a r i t h m e t i c m e a n error of m e a s u r e m e n t o b t a i n e d from repeated measurements. R e s u l t s in Table 2 enable four linear equations to be derived of t h e t y p e K t - - B e + B ~ K e , in w h i c h c o n s t a n t s Be a n d B1 m a y be d e t e r m i n e d b y t h e m e t h o d of least squares [7, 8]. Calculations result in t h e following e q u a t i o n s of lines s i t u a t e d v e r y near the e x p e r i m e n t a l points: Kt(CS,)-- 138.86--16-85Kc~ (CC1,) Kt(CS~)-- 141.50-15.52Kc2 (CC1,) Kt(CC1,) -- 117.03-14.46Ke~(CC1,) Kt(CC1,) = 120.57-13.61Kc. (CC1,).
Spectroscopic determination of content of trans and cis units in polypentenamere
231
I t is evident t h a t with linear extrapolation of Kt values to zero values of Kc the relevant unknowll molar coefficients of extinction of the band of trans units et m a y be obtained and when K t ~ 0, the molar coefficients of extinction of the band of cis units ec (Table 3), derived. TABLE
2. V A L U E S OF K t A N D
Kc
OF P P M
SAMPLES I N SOLUTIOI~S I N C S z A N D C C I 4
W I T H T W O M E T H O D S OF D R A W I N G T H E BASE L I N E OF
T H E B A N D OF C ~ U N I T S
Values of Kt and Ke, mole -~ 1. cm -x Kcl (CCId), Kc2 (CC14), Kt(CC1,) first method second method
Sample, No. Kt(CS,)
121.04-3.0 100.44-2.0 77.04-1.1 55.04-1.2 36.14-0.7 12-14-0.2
92.74-2-5 64.04-2.O 48.74-1.5 16.44-0-5
1.104-0.04 1.304-0.02 2.604-0.02 4-204-0.10 5.704-0-06 7.264-0.05
1-424-0.04 1.604-0-01 3.034-0.06 4.804-0.10 6.304-0.10 7.954-0.10
As an example the result of analysing sample 7 (Table 1 ) in CCI~ solution m a y be given. Using coefficients e t ~ l l 7 and 8c~8.1 ct~83.7 and c ~ 1 4 . 0 ° / o were derived. The overall content of unsaturation is 97.7 ~/o which is in satisfactory agreement with the value obtained by N'MR and a chemical method. TABLE
3. M O L A R
COEFFICIENTS
OF E X T I N C T I O N OF B A N D S
OF
trans A N D ci8 U N I T S OF P P M
Using the base line of the cis band
Values of K t and K c, mole -l 1. cm -~ solutions in CS~ and CC1,
solutions in CC14
et (CS~)
e~ (CC14)
et (CC1,)
8c (CC14)
139 142
8.2 9-1
117 121
8.1 8.9
Results indicate t h a t for a full analysis of PP M samples solutions in CCI4 can only be used. I t is known t h a t in the 1000 cm -I region CC14 is subject to absorption, however, transmission is not less than 35~o with absorption layer thicknesses of up to 0-04 cm. U n d e r these conditions the outline of the band of the substance examined is not distorted [9]. This somewhat restricts the range of application of the analytical method described. However, practice indicates t h a t P P M with a limiting viscosity in toluene at 25 ° of up to 6-7 dl/g with a content of trans bonds of over 8-10~o , m a y be safely analysed in CC14 solutions. I n other words, the method can be u s e d to analyse most P P ~ used for practical purposes, which is v e r y significant if we bear in mind the lower toxicity and volatility of CCl~ compared with carbon disulphide. I t is fairly complicated [10] to evaluate the mean square deviation of experiment when both values (Kt and Kc) are measured with some inaccuracy. We therefore evaluated the errors involved by using the arithmetic mean error and calculating the band bounded by two lines. I t appeared t h a t the error of the extrapolated value of 8t is 4-2.5 of unity (in GC1,) and -b4.5 (in carbon disulphide) and ee-}-(0"l-0"15) of unity. This involves an error in determining trans bonds in :PPI~ of ~ 2.5% (from CC14) and ~ 3% (from carbon disulphide)
232
A . P . ~4~OROBKOet al.
a n d c6~ units, ~ 2%. The accuracy of these estimates is confirmed b y calculating the mean square deviation of et and the correlation coefficient between et and e¢ assuming that the error involved in measuring Ke m a y be ignored (Table 4). T~BLE
4. R O O T MEAN S Q U A R E E R R O R (•)
OF T H E
E X T R A P O L A T E D V A L U E S OF gt A N D C O E F F I C I E N T S OF C O R R E L A T I O N (p) B E T W E E N
Base line of the c/s b a n d 1 2
Solutions in CSs and CCI~
8 t A N D ~c
Solutions in CC14
o-
p
~-
p
4.3 3.7
--0.56 --0.59
2.2 1.9
--0.57 --0.59
The error of measuring K¢ should be considered according to a former study [10] a n d involves some increase in the mean square deviation of the value of ct. Finally, the authors wish to t h a n k L. N. Kurkovskaya and N. N. Shapet'ko for their help in carrying out NMR measurements. Translated by E. SE~ERE
REFERENCES 1. C. TOSSI, F. CIA_MPELLI and G. DALI.'ASTA, J. Polymer Sci. Polymer Phys. Ed. 11: 529, 1973 2. G. I~ATTA, (L DALL'ASTA and G. MAZZANTI, Angew. Chemie 76: 765, 1964 3. R. J. MI~CHAK and H. TUCKER, Polymer Preprints 13: 885, 1972 4. G-. D),I.L'ASTA and 6~. MOTRONI, Angew. Makromolek. Chem. 16/17: 51, 1971 5. T. S. LEE, I. M. KOLTHOFF and M. A. MAIRS, J. Polymer Sci. 3: 66, 1948 6. N. V. KOZLOVA, F. F. SIYKHOV and V. P. BAZOV, Zavodsk. lab. 31: 968, 1965 7. K. P. YAKOVLEV, Matematicheskaya obrabotka rezul'tatov izmerenii (Mathematical Analysis of Results of Measurements). GITL, 1950 8. I~. DREIPER a n d (L SMITH, Prikladnoi regressionnyi analiz (Applied Regression Analysis). Statistika, 1973 9. K. NAKANISI, Infrakrasnye spektry i stroyeniye organicheskikh soyedinenii (IR Spectra a n d Structure of Organic Compounds). Izd. "Mir", 1965 10. V. V. FEI)OROV, Teoriya optimal'nogo eksperimenta, (Theory of Optimum Experiment). Izd. "Nauka", 1971