- Email: [email protected]
IR spectroscopic study of the copolymers of ethylene with vinylcyclohexane
V. L. KHODZHAYEVAet at.
137o
8. N. G. OSIPENKO, E. S. PETROV, Yu. I. RANNEVA, Ye. M. TSVETKOV aad A. I. SHATENSHTEIN, Zhurn. obshch, khimii 47: 2172, 1977 9. A. Yu. PRORUBSHCHIKOV, N. G. KUZINA, A. D. LYKOV, P. N. RESHETOV, L. N. MASHLYAKOVSKI and B. L IONIN, Zhurn. obshch, khimii 52: 1793, 1982 10. L. N. MASHLYAKOVSKII and B. I. IONIN~ Zhurn. obshch, khimii 35: 1577, 1965 11. L. N. MASHLYAKOVSKII, T. A. ZAGUDAYEVA, B. L IONIN, L S. OKHRIMENKO and A. A. PETROV, Zhurn. ohshch, khimii 42: 2648, 1972 12. L. N. MASHLYAKOVSKII, K. A. MAKAROV, L S. OKHRIMENKO and A. F. NIKOLAYEV, Vysokomol. soyed. B12: 451, 1970 (Not translated in Polymer Sci. U.S.S.R.) 13. L V. TAL'VIK and V. A. PAL'M, Reaktsionnaya sposobnost' organicheskikh soyedinenii 8: 445, 1971 14. A. F. PODOL'SKII, S. R. RAKHIMOVA, E. U. URINOV, M. A. AKSAROV and I. A. ARBUZOVA, Uzb. khim. zh., 5, 49, 1973 15. A. A. KOROTKOV and S. P. MITSINGENDLER, Vysokomol. soyed. AI0: 2145, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 9, 2497, 1968) 16. N. A. PLATE and V. V. MAL'TSEV, Sb. mater. Mezhdunar. simpoz. IYuPAK po makromolekulyarnoi khimii (Abstracts of Papers, International Symposium on Macromolecular Chemistry, IUPAC), Budapest, vol. 2, p. 27, 1969 17. S. J. WHICHLER and J. L. BACK, J. Polymer Chem. Ed. 19: 1995, 1981 18. G. N. ARKHIPOVICH, S. A. DUBROVSKH, K. S. KAZANSKII and A. N. SHCHUPIK, Vysokomol. soyed. A23: 1653, 1981 (Translated in Polymer Sci. U,S.S.R. 23: 7, 1827, 1981) 19. V. A. BARABANOV and S. L. DAVYDOVA, Vysokomol. soyed. A24: 899, 1982 (Translated in Polymer Sci. U.S.S.R. 24: 5, 1007, 1982) 20. P. A. BERLIN, V. P. LEBEDEV, A. A. BAGATLIRYANTS and K. S. KAZANSKII, Vysokomol. soyed. A22: 1600, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 7, 1754, 1980) 21. K. S. KAZANSKII and N, G. SPASSKII, Vysokomol. soyed. B24: 203, 1982 (Not translated in Polymer Sci. U.S.S.R.)
Polymer Science U.S.S.R. Vol. 30, No. 6, pp. 1370-1377, 1988
Printed in Poland
0032-3950/88 $10.00+.00 © 1989 Pergamon Press plc
IR SPECTROSCOPIC STUDY OF THE COPOLYMERS OF ETHYLENE WITH VINYLCYCLOHEXANE* V. L. KHODZHAYEVA, YE. L. POLOTSKAYA, V. I. KLEINER, V. G. ZAIKIN a n d B. A. KRENTSEL' A. V. Topchiev Institute of Petrochemical Synthesis, U.S.S.R. Academy of Sciences
(Receh~ed 19 January 1987) The copolymerization products of ethylene with vinylcyclohexane were studied by the IR spectroscopic method. A method for the determination of copolymer composition in the range of 1 to I0 mole ~ of vinylcyelohexane was developed. The composition was calculated * Vysokomol. soyed. 30: No. 6, 1306-1311, 1988.
IK spectroscopic stucly oI copolymers oi ethylene w~tn vmyicyc~onexane
a~ ~
from the analytical bands at 1260 and 2016 cm- 1 by two methods: using band absorbance coefficients computed from copolymer spectra, and from mechanical mixtures of the homopolymers. The results of the two methods were in good agreement. Some copolymer properties (crystallinity, melting temperature, density) were studied for dependence on composition.
IN RECENT years, m u c h a t t e n t i o n is being p a i d to studies o f the m e t h o d s o f p r e p a r a t i o n a n d o f the p r o p e r t i e s o f linear p o l y e t h y l e n e o f low density, the p r o d u c t o f i o n i c - c o o r d i n a t i o n c o p o l y m e r i z a t i o n o f ethylene with small a m o u n t s o f ~-olefins [1]. H o w e v e r , to this d a y L D P E is p r e p a r e d m o s t l y with linear higher ~-olefins. Nevertheless, the a p p l i c a t i o n o f b r a n c h e d ~-olefins like vinylcyclohexane (VCH), 3-methylbutene-1, m e t h y l p e n t e n e etc. to this e n d appea~'s as highly perspective. In this c o n n e c t i o n t h e r e arises the p r o b l e m o f d e t e r m i n i n g the c o m p o s i t i o n a n d s t r u c t u r e o f the c o p o l y m e r s o f ethylene with b r a n c h e d higher ~-olefins. T h e present p a p e r is d e v o t e d to the d e t e r m i n a t i o n , by 1R s p e c t r o s c o p y , o f the structure a n d c o m p o s i t i o n o f ethylene c o p o l y m e r s c o n t a i n i n g 1-10 m o l e ~o V C H , and to the c h a r a c t e r i z a t i o n o f some p r o p e r t i e s o f these c o p o l y m e r s . Ethylene copolymers with VCH, PE and polyvinylcyclohexane (PVCH) were prepared by suspension polymerization of the corresponding monomers in an inert diluent-n-heptane at 70 °, initial ethylene pressure of 0.7 MPa, initial VCH concentration 0.05-2 mole/1., in the presence of a model catalytic system TiCI4 and AI(i-C4Hq), TiCI4 concentration 0.05 mole/I, and molar ratio A I : T i = 3 [2]. The sample of atactic PVCH was the ether-soluble PVCH fraction, of isotactic P V C H - t h e fraction insoluble in boiling n-heptane. For the interpretation of PVCH and copolymer spectra, ethylcyclohexasle, 1,4-dicyclohex ylbutane, l,l-dicyclohexylethane and t,2-dicyclohexylethane were used as model compounds. IR spectra were recorded with the spectrophotometers "Perkin-Elmer" (model 577) and "Specord 1R-75". The samples of copolymers and of mechanical homopolymer mixtures were prepared in the form of films by heat pressing at 140 °. Film thickness was varied from 0'3 to 1.5 mm, in dependence on the copolymer composition. To compensate for background absorption at 1300 cm-1, a PE film of corresponding thickness was placed in the reference beam. Data on absorption band polarization were obtained from spectra of oriented samples in polarized light. Orientation was achieved by uniaxial drawing of copolymer and PVCH films at 20 and 140 °, respectively. Copolymer and PE films were annealed for 6 hr at 120 ° and then cooled to 20 ° in the course of 1-5 hr. Polymer density was determined by the flotation method according to GOST (State norm) 16338-77, the melting temperature of the samples fi'om DTA curves measured with a differential scanning calorimeter (Hungary) in the dynamic mode, with the rate of temperature increase 5 deg/min and sensitivity 500 inV. The s p e c t r a o f P E a n d P V C H , a n d o f the e t h y l e n e - V C H c o p o l y m e r i z a t i o n p r o d u c t s a r e shown in Fig. 1. T h e s p e c t r a o f the c o p o l y m e r i z a t i o n p r o d u c t s a r e n o t an additive u p e r p o s i t i o n o f P E a n d P V C H spectra. This indicates true c o p o l y m e r f o r m a t i o n , as c o n f i r m e d by the results to be f u r t h e r discussed,. F o r studies o f c o p o l y m e r s t r u c t u r e and selection o f a n a l y t i c a l b a n d s i n d e p e n d e n t o f b l o c k length a n d crystallinity, the s p e c t r a o f a t a c t i c a n d isotactic PV(3H in films a n d solution were a n a l y z e d , as well as the s p e c t r a o f c o p o l y m e r melts. W h i l e the s p e c t r u m o f P E has been well investigated, the i n t e r p r e t a t i o n o f the vibra-
V. L. KHODZHAYEVA
et
al.
•
t2
I
!
.,
8
I
I'
I
12
16
20 p. lO-Z~cm -1
b
g
g 1 I
I
I
8
12
16
I
20 V ~lO'~ c m ' l
FIG. 1. ]R spectra of films, a: ]-atactic PVCH, 2-isotactic PVCH, 3 - PE; b-copolymer of
ethylene with 8 mole% VCH at film thickness0.5~mmwithout compensation(I) and with PE film in the reference beam (2). tional spectrum of PVCH has not been fully elaborated so far. Therefore we tried to assign the main absorption bands in the spectrum of PVCH. According to X-ray data, the macromolecules of crystalline isotactic PVCH assume the conformation of a 41 helix (modification I) and of a 247 helix (modification II) [3]. In the PVCH spectrum, localized vibrations of the cyclohexane ring can be recognized, appearing also in the spectra of ethylene-VCH copolymerization products. The corresponding bands can be used as analytical for determining copolymer composition. The bands were assigned by comparison of PVCH spectra with the calculated vibrational spectra of methyl- and ethylcyclohexane [4], and experimental spectra of low-molecular
IR spectroscopic study of copolymers of ethylene with vinylcyclohexane
1373
monosubstituted cyclohexanes. In this assignment, data were used on band dichroism in spectra of oriented films of isotactic PVCH (Table l). The PVCH spectrum contains bands with frequencies and intensities dependent on polymer stereoregularity-l197, 1170, 998, 970, 955, 760cm -~. A comparison of PVCH spectra with those of other polyolefins, and also of PS and of its derivatives indicates, that these bands include contributions from backbone vibrations, bending vibrations of methylene groups, of the ~-hydrogen atom, and of carbon atom stretching vibrations [5-7]. The effect of PVCH stereoregularity is particularly apparent on the bands in the range 1000-700 era- ~ which are sensitive to the angle of helix twist and to the length of isotactic polyolefin blocks (polypropylene, polybutene-1, poly-3-methytbutene-l, poly- 1-methylpentene- 1). The spectrum of isotactic PVCH exhibits medium intensity bands at 955 and 998 cm-~; the frst of these bands is absent in the spectrum of the atactic sample, and the second is of lower intensity. The band at 970 cm- ~ characteristic of the atactic polymer, is absent from the spectrum of isotactic PVCH. The spectra of copolymerization products exhibit all these three bands, but their relative intensities depend on the contents of VCH. The band at 955 cm- ~ appears only as weak absorption in the spectra of copolymers with a sufficiently high contents of VCH (,-~30 ~) and is practically absent from the spectra of copolymers in the studied range of VCH concentrations. ~,9/cm 3
ogee f t/ ~ ~ g ~
T,s5i ,~,,," - 0.9600
10
20
30 Overt, mole%
0.9qO0
5
7O
I 15CVCH,mO&%
Fro. 2 Fro. 3 FIG. 2. Dependence of Da9a/Dtoao on composition of copolymer. Fro. 3. Dependence of the melting temperature (1) and of density (2) on copolymer composition. [n Fig. 2 the ratio of optical densities of the bands at 998 cm- 1 and 1030 cm- t (the latter characteristic of the cyciohexane ring) is plotted in dependence on VCH contents in the copolymer, evcH, as determined by the below described method. When Cvcn changes from 30 to 8 ~ , the ratio decreases fi'om 1 to 0.6, while for isotactic PVCH this ratio is equal to 2 with a film, and to 1.5 in the spectrum of a 3 ~ solution in CC14. The relative intensity of the band at 998 cm-1 is also lowered in the copolymer melt. The above stated indicates that each of the bands at and 998 cm- 1 corresponds to some critical length of the regular helix. The band at cm-1 corresponds to relatively long isotactic blocks, practically absent in atactic PVCH and in VCH copolymers with
D998/Dloao
955 955
i3")4
V.L. KHODZHAY]~VA ~f al.
TABLE 1. VIBRATIONS OF THE CYCLOHEXANE RING OF
Wave number v, cm- t 1452 v.s. 1345m 1335m 1328m 1260m 1218m
Polarization
Vibration
PVCH IN
Wave number v, cm- 1
THE MEDIUM
IR
SPECTRAL ~ANG~
Polarization
Vibration
O"
~A'
O"
flA"
1030 m 892 s
O"
fl,4"
848 s
QA" QA"
O"
pA' (CH) #,4' flA' (CH)
820 m 510
flA" ~'A"
O" 7t
QA'
Note. • and ~ designate polarization parallel and perpendicular with respect to the film stretching direction; Q is the change in. the length of C - C bonds; at, B, ~' are changes in the angles / C , N / C \ and / C , ~ , respectively; A' and A'" aro vibraH HH C C C tions symmetrical and antisymmetrlcal with respect to the symmetry plane of the monosubstitut©d ring.
ethylene, at least in the studied VCH concentration range. The band at 998 cm - t corresponds to relatively short isotactic blocks, present in small amounts even in the atactic polymer; in copolymers the number of these blocks decreases with decreasing even, and with reduced stability of helical segments during polymer melting. The weakly pronounced o'-dichroism of the band at 998 cm-1, contradicting the expected polarization of the helical conformation [8], may be explained by the superposition of bands corresponding to various vibration types. Copolymerization of VCH with ethylene results in a change of the shape of the skeletal vibration band of the cyclohexane ring, observed as a doublet at 892-884 cm- 1 in the PVCH spectrum, with equal ~r-polarization of both components. The doublet structure of the band is independent of stereoregularity and crystallinity; it is observed in the spectra of both tsotactic and atactic polymers, and is preserved in the solution spectrum. By "intramolecular dilution" in VCH copolymerization with ethylene, the intensity of the doublet component at 884 cm- ~ decreases, and at low Cvca values the 884 cm-1 component is only manifested by an insignificant asymmetry of the 892 cm-1 band. Evidently in copolymer spectra, the intensity of this band depends on VCH contents in blocks in general, irrespective of their stereoregularity, while the critical block length may be very small. The sensitivity of the 884 cm- 1 band to unit distribution has also been observed in the case of VCH copolymers with 4-methylpentene-I and styrene [2]. Two other bands corresponding to cyclohexane ring vibrations, 848 and 820 cm- 1, are also sensitive to stereoregularity: In the spectrum of isotactic PVCH they appear as sharp bands, in the spectrum of the atactic polymer as a relatively weak absorption between the above two frequencies. The spectrum of the copolymer in this range appears as a superposition of the spectra of atactic and isotactic PVCH. The above described changes in the range 1000-800 cm -1, observed in the spectra of copolymerization products of VCH with ethylene, as compared to those of PVCH, indicate, on the one hand, the formation of true copolymers, and on the other hand, a considerable structural sensitivity of all bands, including the skeletal vibrations of the cyclohexane ring. The dependence of the band intensities of skeletal ring vibrations on
IR spectroscopic study of copolymers of ethylene with vinylcyclohexane TABLE 2. EFFECT OF ANNEALING ON THE OPTICAL DENSITIES OF THE BANDS AT
i Sample
v, cm- ~
Polyethylene
1894 2016 1894 2016 1894 2016
Copolymer (2 % VCH) Copolymer (10 % VCH)
1375
1894 AND 2016 cM-1
D/d* before annealing 2"77 4'41 2.27 4.01 1.54 2.88
after annealing 3-12 4-48 2.50 3.93 1.69 2.93
AD/Dx 100 % + 12.6 + 1.6 + 10.1 -2.0 + 9.7 + 1.7
* d is the thickness of the film in cm.
stereoregularity and block character limits their applicability as analytical bands. Therefore the medium intensity band at 1260 c m - 1 corresponding to external bending vibrations of ring methylene groups, which is insensitive to stereoregularity and crystallinity, was selected as analytical, corresponding to VCH contents in the copolymer. TABLE 3. COMPOSITIOI~ OF E T H Y L E N E - V C H
VCH contents in initial reaction mixture, mole/l. 0-05 0.12 0.20 0.37 0.43 0.70 1-00
COPOLYMERS
VCH contents in copolymer, mole % calibration with i calibration with mechanical mixtures ] copolymers 0'9 1'0 1"7 2.0 3.6 3-9 7"9 8-5 10"3 10-8 16.7 16.5 21-7 20.5
~, rel. % + 10-0 + 15'0 +7.7 +7.0 +4"6 - 1"2 -5"8
In view of the low absorbance coefficient of this band and the relatively low contents of VCH in the copolymers in the studied composition range, the combination band at 2016 c m - ~ with a low absorbance coefficient was selected as the analytical band characteristic of ethylene units. The band at 2016 cm-~ appears in the spectra of both liquid and solid n-paraffins; in the spectrum of PE it is assigned as a combination of the frequencies 12957t(CH2) + 7307r(CH2) and 13037t((3H2) + 720),,(CH2) [9]. The possible effects of polyethylene type crystallinity on the intensity of the band at 2016 cm -1 in copolymers with low contents of VCH were tested with annealed samples of copolymer films, using the "crystalline" band at 1894 c m - I as control [9]. From Table 2 it can be seen that annealing of polymer films leads to an intensity increase by 10-12 ~o of the band at 1894 cm-1, while the intensity of the band at 2016 cm-1 remains unchanged and varies within the limits of experimental error for Did (+2 %). Two calibration procedures were used for the analytical bands at 1260 and 2016 c m - ' : u s i n g mechanical homopolymer mixtures, and based on the relative absorbance coefficients of these bands, calculated from the spectra of several copolymer samples of various composition.
1376
V.L. KHODZHAYEVAet
at.
The calibration curve, constructed by the least squares method for mechanical mixtures, has the form C~cn= 4"273 xD126o/D2oie, where C~CHis the mole ~ of VCH units in the copolymer. Accuracy of measurement + 6 rel. %. In the second calibration method, the relative absorbance coefficients of the bands 1260 and 2016 eva-1 were calculated for two copolymer samples of various composition, assuming the sum of the molar component fraction in the copolymer to be equal to one !
!
320 x__.___+66 D1260 K2016 ~ = P
II 32016
idl,
~r
K20te
Dll 1260
= p lldll, K1260
where D and K are the optical density and absorbance coefficients of the bands, p and d are the density and film thickness for the samples of copolymers I and II. With this calibration method, the analytical expression for the determination of composition has the form ¢p
F
.
I/Kt260
D1260\'1
cvo.=[3,2.o/32OlO11 . + ) ] ×1oo, where
Kt26o/K2ot6 =
19"77, as determined from four pairs of copolymer samples.
The results of the two methods are in sufficiently good agreement. The difference u = 100(c~,~a-C~Cn)/C~PcH is the least around CVCH" 10% and lies within experimental error (Table 3). Greater differences of opposite sign were observed at high and low CVCHvalues, amounting to + 10-15 ~ at Cvcn = 1-2 ~ , and - 5.8 ~o at Cvcn = 20 ~ . Such dependence of • on composition is explained by structural differences between copolymers and mechanical homopolymer mixtures, and could be corrected for if accurate data on monomer unit distribution in the copolymer were available. Thus the calibration with mechanical homopolymer mixtures, where PE serves simultaneously as a matrix for obtaining contrast spectra of PVCH and as one component of the mixture, can be successfully applied for analyzing the composition of ethylene copolymers with low contents of VCH. Particularly the preparation of samples in the form of thick films (up to 1.5 mm) and the application of the combination vibration at 2016 c m - 1, with a low absorption coefficient, eliminates the well known difficulties ' connected with the measurement of a weak absorption of a hydrocarbon monomer on the background of the strong absorption of t h e main polyethylene component. The effect of copolymer composition on polyethylene type crystallinity was determined by means of the band at 1894 c m - 1 DCp
/3PE
1894. x,"2016 /3PE L-'2016 u 1 8 9 4
/CoP~--"NPE 13cp
where xcp and lops are the mole fractions of the crystalline phase in the copolymer and in the reference PE sample, respectively. The introduction of 2 9/0 VCH units reduces the crystallinity from 70 ~ in PE to 64 in the copolymer, at 10 9/0 VCH, crystallinity of the copolymer decreases to 58 ~ . The drop of crystallinity in copolymers containing small amounts of VCH units correlates with the decrease in density and melting temperature with increasing VCH contents in the copolymer (Fig. 3). Translated by D. DOSKO~ILOV~
Thermodynamic stability of poly(methyl methacrylate)-polycarbonate blends
1377
REFERENCES
I. Ye. B. VESELOVSKAYA, N. N. SEVEROVA, F. I. DUNTOV, A. P. GOLOSOV, A. N, KARASEV, A. L. GOLDENBERG, T. V. KREITSER and V. I. BUKHGALTER, Sopolimery etilena (Ethylene Copolymers), p. 224, Leningrad, 1983 2. B. A. KRENTSEL, V. L KLEINER and L. L. STOTSKAYA, Vysshiye poliolefiny (Higher Polyolefins), p. 184, Moscow, 1984 3. H. D. NOETHER, J. Polymer Sci. C, 16, 725, 1967 4. G. A. ALEKSANDROV, Optika i spektroskopiya 5: 128, 1958 5. P. PAINTER, M. COLEMAN and G. KOENIG, Teoriya kolebatel'noi spektroskopii. Prilozhenie k polimernym meterialam (Theory of Vibrational Spectroscopy and its Applications to Polymeric Materials). p. 580, Moscow, 1986 6. G. M. SEMENOVICH and T. S. KHROMOVA, Spravochnik po fizicheskoi khimii polimerov (Handbook of the Physical Chemistry of Polymers). vol. 3, p. 24, Kiev, 1985 7. J. DECHANT, R. DANZ, V. KIMMER and R. SCHMOLKE, Infrakrasnaya spektroskopiya polimerov (Infrared Spectroscopy of Polymers). p. 472, Moscow, 1976 8. G. Y. LIANG and F. G. PEARSON, J. Molec. Spectroscop. 5: 290, 1960 9. S. KRIMM, Fortschritte der Hochpolymeren-Forschung 2: 1, 51, 1960
Polymer Science U,S,S.R. V01. 30, No. 6, pp. 1377-1381, 1988 Printed in Poland
0032-3950/88 $10.00+.00 pie
© 1989 Pergamon Press
THERMODYNAMIC STABILITY OF POLY(METHYL METHACRYLATE)-POLYCARBONATE BLENDS. EFFECT OF HISTORY AND STRUCTURE* L. V. ADAMOVA, A. A. TAGER, I. N. RAZINSKAYA, V. A. IZVOZCmKOVA, V. P. LEBEDEV, N. T. NERUSH a n d A. M. KORNEV A. M. Gor'kii Ural State University
(Received 20 January 1987) The effect of sample preparation method on structure and on the Gibbs free energy of mixing in poly(methyl methacrylate)-polycarbonate blends is discussed. Blends prepared from solutions containing a partially crystalline p o l y m e r - p o l y c a r b o n a t e - a r e thermodynamically unstable over the whole range of composition, whilst blends prepared from melt represent metastable biphasic systems. Two contributions to the Gibbs free energy of mixing have been identified; one is given by the chemical nature of components, the other depends on their dispersity. IT tS a well e s t a b l i s h e d fact t h a t p o l y m e r blends d u r i n g their p r e p a r a t i o n a n d subsequent utilization often exist in a state far f r o m equilibrium. Such m e t a s t a b l e colloid systems [1] with p r o p e r t i e s d e p e n d i n g on the m e t h o d used for their p r e p a r a t i o n (on * Vysokomol. soyed, A30: No. 6, 1312-1315, 1988.
137o
8. N. G. OSIPENKO, E. S. PETROV, Yu. I. RANNEVA, Ye. M. TSVETKOV aad A. I. SHATENSHTEIN, Zhurn. obshch, khimii 47: 2172, 1977 9. A. Yu. PRORUBSHCHIKOV, N. G. KUZINA, A. D. LYKOV, P. N. RESHETOV, L. N. MASHLYAKOVSKI and B. L IONIN, Zhurn. obshch, khimii 52: 1793, 1982 10. L. N. MASHLYAKOVSKII and B. I. IONIN~ Zhurn. obshch, khimii 35: 1577, 1965 11. L. N. MASHLYAKOVSKII, T. A. ZAGUDAYEVA, B. L IONIN, L S. OKHRIMENKO and A. A. PETROV, Zhurn. ohshch, khimii 42: 2648, 1972 12. L. N. MASHLYAKOVSKII, K. A. MAKAROV, L S. OKHRIMENKO and A. F. NIKOLAYEV, Vysokomol. soyed. B12: 451, 1970 (Not translated in Polymer Sci. U.S.S.R.) 13. L V. TAL'VIK and V. A. PAL'M, Reaktsionnaya sposobnost' organicheskikh soyedinenii 8: 445, 1971 14. A. F. PODOL'SKII, S. R. RAKHIMOVA, E. U. URINOV, M. A. AKSAROV and I. A. ARBUZOVA, Uzb. khim. zh., 5, 49, 1973 15. A. A. KOROTKOV and S. P. MITSINGENDLER, Vysokomol. soyed. AI0: 2145, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 9, 2497, 1968) 16. N. A. PLATE and V. V. MAL'TSEV, Sb. mater. Mezhdunar. simpoz. IYuPAK po makromolekulyarnoi khimii (Abstracts of Papers, International Symposium on Macromolecular Chemistry, IUPAC), Budapest, vol. 2, p. 27, 1969 17. S. J. WHICHLER and J. L. BACK, J. Polymer Chem. Ed. 19: 1995, 1981 18. G. N. ARKHIPOVICH, S. A. DUBROVSKH, K. S. KAZANSKII and A. N. SHCHUPIK, Vysokomol. soyed. A23: 1653, 1981 (Translated in Polymer Sci. U,S.S.R. 23: 7, 1827, 1981) 19. V. A. BARABANOV and S. L. DAVYDOVA, Vysokomol. soyed. A24: 899, 1982 (Translated in Polymer Sci. U.S.S.R. 24: 5, 1007, 1982) 20. P. A. BERLIN, V. P. LEBEDEV, A. A. BAGATLIRYANTS and K. S. KAZANSKII, Vysokomol. soyed. A22: 1600, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 7, 1754, 1980) 21. K. S. KAZANSKII and N, G. SPASSKII, Vysokomol. soyed. B24: 203, 1982 (Not translated in Polymer Sci. U.S.S.R.)
Polymer Science U.S.S.R. Vol. 30, No. 6, pp. 1370-1377, 1988
Printed in Poland
0032-3950/88 $10.00+.00 © 1989 Pergamon Press plc
IR SPECTROSCOPIC STUDY OF THE COPOLYMERS OF ETHYLENE WITH VINYLCYCLOHEXANE* V. L. KHODZHAYEVA, YE. L. POLOTSKAYA, V. I. KLEINER, V. G. ZAIKIN a n d B. A. KRENTSEL' A. V. Topchiev Institute of Petrochemical Synthesis, U.S.S.R. Academy of Sciences
(Receh~ed 19 January 1987) The copolymerization products of ethylene with vinylcyclohexane were studied by the IR spectroscopic method. A method for the determination of copolymer composition in the range of 1 to I0 mole ~ of vinylcyelohexane was developed. The composition was calculated * Vysokomol. soyed. 30: No. 6, 1306-1311, 1988.
IK spectroscopic stucly oI copolymers oi ethylene w~tn vmyicyc~onexane
a~ ~
from the analytical bands at 1260 and 2016 cm- 1 by two methods: using band absorbance coefficients computed from copolymer spectra, and from mechanical mixtures of the homopolymers. The results of the two methods were in good agreement. Some copolymer properties (crystallinity, melting temperature, density) were studied for dependence on composition.
IN RECENT years, m u c h a t t e n t i o n is being p a i d to studies o f the m e t h o d s o f p r e p a r a t i o n a n d o f the p r o p e r t i e s o f linear p o l y e t h y l e n e o f low density, the p r o d u c t o f i o n i c - c o o r d i n a t i o n c o p o l y m e r i z a t i o n o f ethylene with small a m o u n t s o f ~-olefins [1]. H o w e v e r , to this d a y L D P E is p r e p a r e d m o s t l y with linear higher ~-olefins. Nevertheless, the a p p l i c a t i o n o f b r a n c h e d ~-olefins like vinylcyclohexane (VCH), 3-methylbutene-1, m e t h y l p e n t e n e etc. to this e n d appea~'s as highly perspective. In this c o n n e c t i o n t h e r e arises the p r o b l e m o f d e t e r m i n i n g the c o m p o s i t i o n a n d s t r u c t u r e o f the c o p o l y m e r s o f ethylene with b r a n c h e d higher ~-olefins. T h e present p a p e r is d e v o t e d to the d e t e r m i n a t i o n , by 1R s p e c t r o s c o p y , o f the structure a n d c o m p o s i t i o n o f ethylene c o p o l y m e r s c o n t a i n i n g 1-10 m o l e ~o V C H , and to the c h a r a c t e r i z a t i o n o f some p r o p e r t i e s o f these c o p o l y m e r s . Ethylene copolymers with VCH, PE and polyvinylcyclohexane (PVCH) were prepared by suspension polymerization of the corresponding monomers in an inert diluent-n-heptane at 70 °, initial ethylene pressure of 0.7 MPa, initial VCH concentration 0.05-2 mole/1., in the presence of a model catalytic system TiCI4 and AI(i-C4Hq), TiCI4 concentration 0.05 mole/I, and molar ratio A I : T i = 3 [2]. The sample of atactic PVCH was the ether-soluble PVCH fraction, of isotactic P V C H - t h e fraction insoluble in boiling n-heptane. For the interpretation of PVCH and copolymer spectra, ethylcyclohexasle, 1,4-dicyclohex ylbutane, l,l-dicyclohexylethane and t,2-dicyclohexylethane were used as model compounds. IR spectra were recorded with the spectrophotometers "Perkin-Elmer" (model 577) and "Specord 1R-75". The samples of copolymers and of mechanical homopolymer mixtures were prepared in the form of films by heat pressing at 140 °. Film thickness was varied from 0'3 to 1.5 mm, in dependence on the copolymer composition. To compensate for background absorption at 1300 cm-1, a PE film of corresponding thickness was placed in the reference beam. Data on absorption band polarization were obtained from spectra of oriented samples in polarized light. Orientation was achieved by uniaxial drawing of copolymer and PVCH films at 20 and 140 °, respectively. Copolymer and PE films were annealed for 6 hr at 120 ° and then cooled to 20 ° in the course of 1-5 hr. Polymer density was determined by the flotation method according to GOST (State norm) 16338-77, the melting temperature of the samples fi'om DTA curves measured with a differential scanning calorimeter (Hungary) in the dynamic mode, with the rate of temperature increase 5 deg/min and sensitivity 500 inV. The s p e c t r a o f P E a n d P V C H , a n d o f the e t h y l e n e - V C H c o p o l y m e r i z a t i o n p r o d u c t s a r e shown in Fig. 1. T h e s p e c t r a o f the c o p o l y m e r i z a t i o n p r o d u c t s a r e n o t an additive u p e r p o s i t i o n o f P E a n d P V C H spectra. This indicates true c o p o l y m e r f o r m a t i o n , as c o n f i r m e d by the results to be f u r t h e r discussed,. F o r studies o f c o p o l y m e r s t r u c t u r e and selection o f a n a l y t i c a l b a n d s i n d e p e n d e n t o f b l o c k length a n d crystallinity, the s p e c t r a o f a t a c t i c a n d isotactic PV(3H in films a n d solution were a n a l y z e d , as well as the s p e c t r a o f c o p o l y m e r melts. W h i l e the s p e c t r u m o f P E has been well investigated, the i n t e r p r e t a t i o n o f the vibra-
V. L. KHODZHAYEVA
et
al.
•
t2
I
!
.,
8
I
I'
I
12
16
20 p. lO-Z~cm -1
b
g
g 1 I
I
I
8
12
16
I
20 V ~lO'~ c m ' l
FIG. 1. ]R spectra of films, a: ]-atactic PVCH, 2-isotactic PVCH, 3 - PE; b-copolymer of
ethylene with 8 mole% VCH at film thickness0.5~mmwithout compensation(I) and with PE film in the reference beam (2). tional spectrum of PVCH has not been fully elaborated so far. Therefore we tried to assign the main absorption bands in the spectrum of PVCH. According to X-ray data, the macromolecules of crystalline isotactic PVCH assume the conformation of a 41 helix (modification I) and of a 247 helix (modification II) [3]. In the PVCH spectrum, localized vibrations of the cyclohexane ring can be recognized, appearing also in the spectra of ethylene-VCH copolymerization products. The corresponding bands can be used as analytical for determining copolymer composition. The bands were assigned by comparison of PVCH spectra with the calculated vibrational spectra of methyl- and ethylcyclohexane [4], and experimental spectra of low-molecular
IR spectroscopic study of copolymers of ethylene with vinylcyclohexane
1373
monosubstituted cyclohexanes. In this assignment, data were used on band dichroism in spectra of oriented films of isotactic PVCH (Table l). The PVCH spectrum contains bands with frequencies and intensities dependent on polymer stereoregularity-l197, 1170, 998, 970, 955, 760cm -~. A comparison of PVCH spectra with those of other polyolefins, and also of PS and of its derivatives indicates, that these bands include contributions from backbone vibrations, bending vibrations of methylene groups, of the ~-hydrogen atom, and of carbon atom stretching vibrations [5-7]. The effect of PVCH stereoregularity is particularly apparent on the bands in the range 1000-700 era- ~ which are sensitive to the angle of helix twist and to the length of isotactic polyolefin blocks (polypropylene, polybutene-1, poly-3-methytbutene-l, poly- 1-methylpentene- 1). The spectrum of isotactic PVCH exhibits medium intensity bands at 955 and 998 cm-~; the frst of these bands is absent in the spectrum of the atactic sample, and the second is of lower intensity. The band at 970 cm- ~ characteristic of the atactic polymer, is absent from the spectrum of isotactic PVCH. The spectra of copolymerization products exhibit all these three bands, but their relative intensities depend on the contents of VCH. The band at 955 cm- ~ appears only as weak absorption in the spectra of copolymers with a sufficiently high contents of VCH (,-~30 ~) and is practically absent from the spectra of copolymers in the studied range of VCH concentrations. ~,9/cm 3
ogee f t/ ~ ~ g ~
T,s5i ,~,,," - 0.9600
10
20
30 Overt, mole%
0.9qO0
5
7O
I 15CVCH,mO&%
Fro. 2 Fro. 3 FIG. 2. Dependence of Da9a/Dtoao on composition of copolymer. Fro. 3. Dependence of the melting temperature (1) and of density (2) on copolymer composition. [n Fig. 2 the ratio of optical densities of the bands at 998 cm- 1 and 1030 cm- t (the latter characteristic of the cyciohexane ring) is plotted in dependence on VCH contents in the copolymer, evcH, as determined by the below described method. When Cvcn changes from 30 to 8 ~ , the ratio decreases fi'om 1 to 0.6, while for isotactic PVCH this ratio is equal to 2 with a film, and to 1.5 in the spectrum of a 3 ~ solution in CC14. The relative intensity of the band at 998 cm-1 is also lowered in the copolymer melt. The above stated indicates that each of the bands at and 998 cm- 1 corresponds to some critical length of the regular helix. The band at cm-1 corresponds to relatively long isotactic blocks, practically absent in atactic PVCH and in VCH copolymers with
D998/Dloao
955 955
i3")4
V.L. KHODZHAY]~VA ~f al.
TABLE 1. VIBRATIONS OF THE CYCLOHEXANE RING OF
Wave number v, cm- t 1452 v.s. 1345m 1335m 1328m 1260m 1218m
Polarization
Vibration
PVCH IN
Wave number v, cm- 1
THE MEDIUM
IR
SPECTRAL ~ANG~
Polarization
Vibration
O"
~A'
O"
flA"
1030 m 892 s
O"
fl,4"
848 s
QA" QA"
O"
pA' (CH) #,4' flA' (CH)
820 m 510
flA" ~'A"
O" 7t
QA'
Note. • and ~ designate polarization parallel and perpendicular with respect to the film stretching direction; Q is the change in. the length of C - C bonds; at, B, ~' are changes in the angles / C , N / C \ and / C , ~ , respectively; A' and A'" aro vibraH HH C C C tions symmetrical and antisymmetrlcal with respect to the symmetry plane of the monosubstitut©d ring.
ethylene, at least in the studied VCH concentration range. The band at 998 cm - t corresponds to relatively short isotactic blocks, present in small amounts even in the atactic polymer; in copolymers the number of these blocks decreases with decreasing even, and with reduced stability of helical segments during polymer melting. The weakly pronounced o'-dichroism of the band at 998 cm-1, contradicting the expected polarization of the helical conformation [8], may be explained by the superposition of bands corresponding to various vibration types. Copolymerization of VCH with ethylene results in a change of the shape of the skeletal vibration band of the cyclohexane ring, observed as a doublet at 892-884 cm- 1 in the PVCH spectrum, with equal ~r-polarization of both components. The doublet structure of the band is independent of stereoregularity and crystallinity; it is observed in the spectra of both tsotactic and atactic polymers, and is preserved in the solution spectrum. By "intramolecular dilution" in VCH copolymerization with ethylene, the intensity of the doublet component at 884 cm- ~ decreases, and at low Cvca values the 884 cm-1 component is only manifested by an insignificant asymmetry of the 892 cm-1 band. Evidently in copolymer spectra, the intensity of this band depends on VCH contents in blocks in general, irrespective of their stereoregularity, while the critical block length may be very small. The sensitivity of the 884 cm- 1 band to unit distribution has also been observed in the case of VCH copolymers with 4-methylpentene-I and styrene [2]. Two other bands corresponding to cyclohexane ring vibrations, 848 and 820 cm- 1, are also sensitive to stereoregularity: In the spectrum of isotactic PVCH they appear as sharp bands, in the spectrum of the atactic polymer as a relatively weak absorption between the above two frequencies. The spectrum of the copolymer in this range appears as a superposition of the spectra of atactic and isotactic PVCH. The above described changes in the range 1000-800 cm -1, observed in the spectra of copolymerization products of VCH with ethylene, as compared to those of PVCH, indicate, on the one hand, the formation of true copolymers, and on the other hand, a considerable structural sensitivity of all bands, including the skeletal vibrations of the cyclohexane ring. The dependence of the band intensities of skeletal ring vibrations on
IR spectroscopic study of copolymers of ethylene with vinylcyclohexane TABLE 2. EFFECT OF ANNEALING ON THE OPTICAL DENSITIES OF THE BANDS AT
i Sample
v, cm- ~
Polyethylene
1894 2016 1894 2016 1894 2016
Copolymer (2 % VCH) Copolymer (10 % VCH)
1375
1894 AND 2016 cM-1
D/d* before annealing 2"77 4'41 2.27 4.01 1.54 2.88
after annealing 3-12 4-48 2.50 3.93 1.69 2.93
AD/Dx 100 % + 12.6 + 1.6 + 10.1 -2.0 + 9.7 + 1.7
* d is the thickness of the film in cm.
stereoregularity and block character limits their applicability as analytical bands. Therefore the medium intensity band at 1260 c m - 1 corresponding to external bending vibrations of ring methylene groups, which is insensitive to stereoregularity and crystallinity, was selected as analytical, corresponding to VCH contents in the copolymer. TABLE 3. COMPOSITIOI~ OF E T H Y L E N E - V C H
VCH contents in initial reaction mixture, mole/l. 0-05 0.12 0.20 0.37 0.43 0.70 1-00
COPOLYMERS
VCH contents in copolymer, mole % calibration with i calibration with mechanical mixtures ] copolymers 0'9 1'0 1"7 2.0 3.6 3-9 7"9 8-5 10"3 10-8 16.7 16.5 21-7 20.5
~, rel. % + 10-0 + 15'0 +7.7 +7.0 +4"6 - 1"2 -5"8
In view of the low absorbance coefficient of this band and the relatively low contents of VCH in the copolymers in the studied composition range, the combination band at 2016 c m - ~ with a low absorbance coefficient was selected as the analytical band characteristic of ethylene units. The band at 2016 cm-~ appears in the spectra of both liquid and solid n-paraffins; in the spectrum of PE it is assigned as a combination of the frequencies 12957t(CH2) + 7307r(CH2) and 13037t((3H2) + 720),,(CH2) [9]. The possible effects of polyethylene type crystallinity on the intensity of the band at 2016 cm -1 in copolymers with low contents of VCH were tested with annealed samples of copolymer films, using the "crystalline" band at 1894 c m - I as control [9]. From Table 2 it can be seen that annealing of polymer films leads to an intensity increase by 10-12 ~o of the band at 1894 cm-1, while the intensity of the band at 2016 cm-1 remains unchanged and varies within the limits of experimental error for Did (+2 %). Two calibration procedures were used for the analytical bands at 1260 and 2016 c m - ' : u s i n g mechanical homopolymer mixtures, and based on the relative absorbance coefficients of these bands, calculated from the spectra of several copolymer samples of various composition.
1376
V.L. KHODZHAYEVAet
at.
The calibration curve, constructed by the least squares method for mechanical mixtures, has the form C~cn= 4"273 xD126o/D2oie, where C~CHis the mole ~ of VCH units in the copolymer. Accuracy of measurement + 6 rel. %. In the second calibration method, the relative absorbance coefficients of the bands 1260 and 2016 eva-1 were calculated for two copolymer samples of various composition, assuming the sum of the molar component fraction in the copolymer to be equal to one !
!
320 x__.___+66 D1260 K2016 ~ = P
II 32016
idl,
~r
K20te
Dll 1260
= p lldll, K1260
where D and K are the optical density and absorbance coefficients of the bands, p and d are the density and film thickness for the samples of copolymers I and II. With this calibration method, the analytical expression for the determination of composition has the form ¢p
F
.
I/Kt260
D1260\'1
cvo.=[3,2.o/32OlO11 . + ) ] ×1oo, where
Kt26o/K2ot6 =
19"77, as determined from four pairs of copolymer samples.
The results of the two methods are in sufficiently good agreement. The difference u = 100(c~,~a-C~Cn)/C~PcH is the least around CVCH" 10% and lies within experimental error (Table 3). Greater differences of opposite sign were observed at high and low CVCHvalues, amounting to + 10-15 ~ at Cvcn = 1-2 ~ , and - 5.8 ~o at Cvcn = 20 ~ . Such dependence of • on composition is explained by structural differences between copolymers and mechanical homopolymer mixtures, and could be corrected for if accurate data on monomer unit distribution in the copolymer were available. Thus the calibration with mechanical homopolymer mixtures, where PE serves simultaneously as a matrix for obtaining contrast spectra of PVCH and as one component of the mixture, can be successfully applied for analyzing the composition of ethylene copolymers with low contents of VCH. Particularly the preparation of samples in the form of thick films (up to 1.5 mm) and the application of the combination vibration at 2016 c m - 1, with a low absorption coefficient, eliminates the well known difficulties ' connected with the measurement of a weak absorption of a hydrocarbon monomer on the background of the strong absorption of t h e main polyethylene component. The effect of copolymer composition on polyethylene type crystallinity was determined by means of the band at 1894 c m - 1 DCp
/3PE
1894. x,"2016 /3PE L-'2016 u 1 8 9 4
/CoP~--"NPE 13cp
where xcp and lops are the mole fractions of the crystalline phase in the copolymer and in the reference PE sample, respectively. The introduction of 2 9/0 VCH units reduces the crystallinity from 70 ~ in PE to 64 in the copolymer, at 10 9/0 VCH, crystallinity of the copolymer decreases to 58 ~ . The drop of crystallinity in copolymers containing small amounts of VCH units correlates with the decrease in density and melting temperature with increasing VCH contents in the copolymer (Fig. 3). Translated by D. DOSKO~ILOV~
Thermodynamic stability of poly(methyl methacrylate)-polycarbonate blends
1377
REFERENCES
I. Ye. B. VESELOVSKAYA, N. N. SEVEROVA, F. I. DUNTOV, A. P. GOLOSOV, A. N, KARASEV, A. L. GOLDENBERG, T. V. KREITSER and V. I. BUKHGALTER, Sopolimery etilena (Ethylene Copolymers), p. 224, Leningrad, 1983 2. B. A. KRENTSEL, V. L KLEINER and L. L. STOTSKAYA, Vysshiye poliolefiny (Higher Polyolefins), p. 184, Moscow, 1984 3. H. D. NOETHER, J. Polymer Sci. C, 16, 725, 1967 4. G. A. ALEKSANDROV, Optika i spektroskopiya 5: 128, 1958 5. P. PAINTER, M. COLEMAN and G. KOENIG, Teoriya kolebatel'noi spektroskopii. Prilozhenie k polimernym meterialam (Theory of Vibrational Spectroscopy and its Applications to Polymeric Materials). p. 580, Moscow, 1986 6. G. M. SEMENOVICH and T. S. KHROMOVA, Spravochnik po fizicheskoi khimii polimerov (Handbook of the Physical Chemistry of Polymers). vol. 3, p. 24, Kiev, 1985 7. J. DECHANT, R. DANZ, V. KIMMER and R. SCHMOLKE, Infrakrasnaya spektroskopiya polimerov (Infrared Spectroscopy of Polymers). p. 472, Moscow, 1976 8. G. Y. LIANG and F. G. PEARSON, J. Molec. Spectroscop. 5: 290, 1960 9. S. KRIMM, Fortschritte der Hochpolymeren-Forschung 2: 1, 51, 1960
Polymer Science U,S,S.R. V01. 30, No. 6, pp. 1377-1381, 1988 Printed in Poland
0032-3950/88 $10.00+.00 pie
© 1989 Pergamon Press
THERMODYNAMIC STABILITY OF POLY(METHYL METHACRYLATE)-POLYCARBONATE BLENDS. EFFECT OF HISTORY AND STRUCTURE* L. V. ADAMOVA, A. A. TAGER, I. N. RAZINSKAYA, V. A. IZVOZCmKOVA, V. P. LEBEDEV, N. T. NERUSH a n d A. M. KORNEV A. M. Gor'kii Ural State University
(Received 20 January 1987) The effect of sample preparation method on structure and on the Gibbs free energy of mixing in poly(methyl methacrylate)-polycarbonate blends is discussed. Blends prepared from solutions containing a partially crystalline p o l y m e r - p o l y c a r b o n a t e - a r e thermodynamically unstable over the whole range of composition, whilst blends prepared from melt represent metastable biphasic systems. Two contributions to the Gibbs free energy of mixing have been identified; one is given by the chemical nature of components, the other depends on their dispersity. IT tS a well e s t a b l i s h e d fact t h a t p o l y m e r blends d u r i n g their p r e p a r a t i o n a n d subsequent utilization often exist in a state far f r o m equilibrium. Such m e t a s t a b l e colloid systems [1] with p r o p e r t i e s d e p e n d i n g on the m e t h o d used for their p r e p a r a t i o n (on * Vysokomol. soyed, A30: No. 6, 1312-1315, 1988.