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Unperturbed molecular dimensions of atactic polybutene-1 at different temperatures
European PolymerJournal, 1967, Vol. 3 pp. 251-2.57. Pa'samon Pros Ltd. Printod in ~n_~land.
UNPERTURBED
MOLECULAR
POLYBUTENE-1
DIMENSIONS
AT DIFFERENT
OF ATACTIC
TEMPERATURES
G. MORAGHO, G. G t ~ o T r i and F. DANUSSO Istituto di Chimica Influstriale del Politecnico, Milano Centro Nazionale di Chimica delle Macromolecole del C.N.R. Sez. I, Milano
and Montecatini S.p.A. Milano (Received 28 November 1966) Abstract--The unperturbed dimensions of atactic polybutene-1 have been determined by viscosimetric measurements in 0 solvents over the range - 4 6 ° to +83 °. Additional data on unperturbed dimensions, calculated by the Kurata--Stockmayer approximation from studies of solutions in good solvents, are suitable to extend the range of temperature to 100 °. From all calculated and measured quantities, the following temperature coetf~ent is found: d In ~o.103ffi_ 1.2+0. 2 dT This value is compared with that obtained by thermoelastic measurements, which give a positive value for the ¢oemcient: the possible causes for this fact are discussed.
IN RECENTyears, particular attention has been devoted to the conformational parameter (d In r~/(dT), which measures the variation with temperature of the mean-square end-to-end distance of unperturbed molecular chains. This parameter appears in the theory of macromolecular solutions as well as in that of the thermoelastic properties of polymeric materials. Furthermore the temperature coefficient of the unperturbed dimensions has, in fact, wider implications than the dimensions themselves at a fixed temperature, if an accurate understanding of the confignrational and conformational properties of macromolecular chains is to be reached. For several polymers, unfortunately, the values of (d In ~)/(dT) quoted in the literature by different authors are in disagreement not only in value but also in sign. This is particularly the case for measurements in solutions for which more data are reported. •The use of particular theoretical treatments for solutions in good solvents might be one of the main reasons for scatter of the results. For these, values of thermodynamic parameters have frequently to be chosen in an arbitrary way. On the other hand, measurements in 0 solvents may not be free from criticism, if unperturbed dimensions are measured over too limited a range of temperature. It has often been stated that the different nature of the 0 solvents can determine the results. However, as proved in recent work for polyethylene,(1) this effect, if present, should be very small. We will assume that this conclusion is valid also for polybutene- 1, and in this paper we report data of unperturbed dimensions of the atactic isomer of this polymer, obtained by measurements in 0 solvents, over rather a wide range of temperature. 251
252
G. MORAGLIO, G. G I A N O T r l and F. DANUSSO
Some a d d i t i o n a l d a t a will be calculated, a c c o r d i n g to the K u r a t a - S t o c k m a y e r a p p r o x i m a t i o n , f r o m e x p e r i m e n t a l results in solutions in t h e r m o d y n a m i c a l l y favourable solvents; these last d a t a a p p e a r to be in a g r e e m e n t with the results directly o b t a i n e d in 0 solvents a n d further w i d e n the range o f t e m p e r a t u r e examined. EXPERIMENTAL
Samples andfractionation The polymeric samples were all prepared by polymerization with a catalyst derived from VCI( + aluminum diethylmonochloride, followed by ether extraction of the crude polymers.(2) The samples were purified by redissolution, followed by precipitation and drying; they possessed an X-ray crystallinity of only a few units per cent. A sample of polyhutene-1 thus obtained was further extracted at room temperature with a methanolbenzene mixture (13.5/86.5 by volume). The extracted sample, referred to as sample R, did not show any crystallinity by X-ray examination. The residue was further extracted by stirring with a methanol-chloroform mixture (17/83 by volume); the extracted polymer, referred to as sample RR, showed only traces of crystaUinity. Measurements of intrinsic viscosity in toluene at 30° gave, for the R and RR samples, 0.8 and 2 respectively (in 100 em3g--1). Two other samples of polybutene-1 were separately dissolved to give 0"5yo solutions in toluene, and the solutions were cooled to - 10° with stirring for about 6 hr; the soluble parts of the polymers were separated by sedimentation and further by centrifugation: they were precipitated with methanol. The polymers thus obtained are referred to as samples A and B. They showed traces of crystaLlinity by X-rays; their intrinsic viscosities at 30° were respectively 0.5 and 0-7 (in 100 cm3 g-l). Samples R, RR, A and B were fractionated by the usual techniques of fractional precipitation using toluene-methanol as solvent-non solvent pair. Further details of the techniques for the preparation of samples R and RR and for the subsequent fractionations can be found in a previous paper3 z) Solvents Solvents were dehydrated and distilled in a laboratory rectifying column. In particular, toluene for low temperature measurements was dried and rectified with metallic sodium. In all cases, solvents were protected from moisture by dehydrating agents. Viscosity measurements Desreux-Bischoff type viscometers were used.o) One of them was equipped with CaCI2 and P205 traps for low-temperature measurements. Critical temperatures of liquid phase separation They were determined by a suitable apparatus, fitted with a calibrated thermometer and CaC12 and P205 traps. Stirring was by means of a magnetic stirrer. RESULTS AND DISCUSSION I n a previous investigation o n the s o l u t i o n p r o p e r t i e s o f atactic polybutene-1, (4. 5) t w o d a t a were o b t a i n e d o f the u n p e r t u r b e d m o l e c u l a r dimensions in 0-solvents at t w o different temperatures. T h e [ ~ / ] = K M a relations were f o u n d to be [~/] = 11"33.10 - 4 M 0"5 in i s o a m y l a c e t a t e at 23 °
(1)
[7] = 10-51.10 - 4 M °'5 in phenetole a t 61 °
(2)
A first a p p r o x i m a t e value o f (d In r02)/(dT), f r o m (1) a n d (2), was - 1.3 x 10-3. T h e a i m o f the present w o r k is to widen the range o f t e m p e r a t u r e a n d t o refine t h a t deterruination, finding a d d i t i o n a l solvents b e l o w 23 ° a n d a b o v e 61 °. I n o r d e r to find a l o w t e m p e r a t u r e 0 solvent, the d a t a o b t a i n e d in a previous work, cs) interpreted a c c o r d i n g to the F o x - F l o r y t h e o r y o f solutions, suggested t h a t toluene
Unperturbed Dimensions of Atactic Polybutene-I
253
s h o u l d b e c o m e a p s e u d o - i d e a l solvent before r e a c h i n g its freezing point. T h e m o l e c u l a r weights o f several f r a c t i o n s o f s a m p l e s R, R R , A a n d B were m e a s u r e d viscometfically in t o l u e n e a t 30 ° using t h e p r e v i o u s l y stated f o r m u l a :(2.4) [7] = 1"55.10 -4 M 0'725
(3)
T h e values f o u n d are r e p o r t e d in the s e c o n d a n d t h i r d c o l u m n s o f T a b l e 1.* TABL~ 1. IN'rmNslc wsco~'t~s oF FRACTIONSOF ATACTICPOLYBUTENE-1IN TWO 0 SOLVENTSAND MOLECULAR V/EIGHTS CALCULATED BY INTRINSIC VISCOSITYIN TOLUENE AT 30 °(2) ([7] in 100 cm~ g-l)
['1] in toluene Fraction
RR 4222 R 322 R 4222 R 52 R 53 A 112 B 42 R 63 B 62
at 30 °t2)
M. 103
[7] in toluene at --46 °
[71 in anisole at 83 °
1.565 1.301 0.945 0"750 0.690 0.642 0.482 0-476 0.293
335 258 166 121 108 98"0 66.0 64"5 33-0
-0.674 0.540 0.470 0.444 --0"332 --
0.605 0.554 0.453 --0.350 0.274 0"278 0.190
T h e intrinsic viscosities o f s o m e fractions o f samples R a n d R R were then m e a s u r e d a t - 3 0 . 5 , - 3 5 a n d - 4 0 . 5 ° in t o l u e n e so t h a t the e x p o n e n t a o f the [ 7 ] - M r e l a t i o n for this solvent, at different t e m p e r a t u r e s , was d e t e r m i n e d . By e x t r a p o l a t i n g the values o f t e m p e r a t u r e f o r a ffi0.5, the 0 t e m p e r a t u r e f o r a t a c t i c p o l y b u t e n e in t o l u e n e was e s t i m a t e d as - 4 6 ° . A t the a b o v e l o w t e m p e r a t u r e s , the solutions o f the fractions o f s a m p l e s A a n d B show s o m e t u r b i d i t y due t o crystAlliT~tion o f isotactic s t e r e o b l o c k i m p u r i t i e s : the d a t a relating to these fractions in t o l u e n e at l o w t e m p e r a t u r e s have therefore been excluded. T h e n we m e a s u r e d [7] in t o l u e n e a t - 4 6 o f o r m o r e fractions o f s a m p l e R : the results are in t h e f o u r t h c o l u m n o f T a b l e I a n d are p l o t t e d a g a i n s t M in the d o u b l e l o g a r i t h m i c d i a g r a m o f Fig. 1. T h e following r e l a t i o n was d e r i v e d : [7] ffi 13-34.10 - 4 M °'s in toluene at - 4 6 °
(4)
W i t h r e g a r d to 0 solvents a b o v e 61 °, anisol was s h o w n to be a possible p s e u d o - i d e a l solvent. (6) * Samples of polybutene-1 undergo a moderate degradation with time: this causes values of [7] and M, reported in Table 1 and referring to fractions prepared some years ago, to be slightly lower than previously quoted. (2,4,5) The consequent higher polyclispersity of these fractions is thought to be inconsequential for our results.
254
G. MORAGLIO, G. G I A N O T F I and F. DANUSSO
For some fractions, obtained as above by fractional precipitation, the molecular weight was measured. The samples were dissolved in anisol (by heating at about I00 °) at different concentration near to the calculated critical composition, and the temperatures of liquid-liquid separation were determined by slowly cooling the solutions
ATACTIC POLY(BUTENE'1) IN TOLUENE AT - 4 6 °C
r,a
4,8 5.0 5,2 5.4 log I'I FIG, l. Intrinsic viscosities and molecular weights of fractions of atactic polybutene-1 in toluene at - 460: 0 conditions.
during stirring. From the state diagrams reported in Fig. 2a, the values of the critical temperature Tc were determined for the various fractions as the maximum value oftbe separation temperatures. Figure 2b reports T~-1 vs. the function x-I/2+ (2x)-l, x being the ratio between the molar volumes of the various fractions and of the solvent. The average straight line passing through the experimental points gives, by extrapolation, a 0 temperature of 83°.
==~z:. -
-
I Is-~0
2.95
\ 98"000
2.90
/
74 _~
/
66"000
68
~
86
2,85 33"000
/
2.8~
64 0
2
4
6
8
(2a)
10
/2 #
2
4
V=.tO
6
8
(_L.._LI.Io 2
~x" 2xl
(2b)
Fxo. 2. (a). Phase diagram for four fractions of atactic polybutene-1, of known molecular weight, in anisol. (b). Plot of Tc-1 vs. molecular size function [x-Z/z+(2x) -z] (x is the ratio between the molar volumes of polymer and of solvent).
Unperturbed Dimensions of Atactio Polybutene-1
255
The intrinsic viscosities of some fractions were then measured in anisol at 83 °. The values obtained are reported in the fifth column of Table 1, and the same data (Fig. 3) give the equation: [,7]= 10.81.10 -4 M °'5 in anisol at 83 ° (5)
t°~'I[~/]
ArACTIC POLY(BUTENE-1) IN ANISOL AT ,B3°C.
~8
4,6
4.8
5,0
5,2
5,4
log. N
F[o. 3. Intrinsic viscosities and molecular weights of fractions of atactic polybutene-I in anisol at 83°: Oconditions.
The values of log K relative to the various 0 solvents considered, are finally reported vs. temperature in Fig. 4 from which the following mean value can be calculated m
dlnr0: = 2 d l n K . . . . dT 3 dT
1-2.10 -3 (_+0-2.10-3 )
(6)
tog K E,tO ~,,I0 ~.0
-50 0 S0 I00 t °C FIG. 4. Plot of the unperturbed l~'ameter log K vs. temperature.
Although the measurements in 0 solvents should give more reliable values, we also determined some additional K values referring to unperturbed conditions from experimental data of [7] in good solvents, reported in previous papers (4, 7) by applying the Kurata-Stockmayer approximation. (s) This treatment has actually proved in many instances to give results of unperturbed dimensions largely independent of the solvent used, and in good agreement with those experimentally obtained with pseudo-ideal solvents. In addition, it can be applied without a previous choice of thermodynamic parameter values.
256
G. MORAGLIO, G. GIANOTTI and F. DANUSSO
Figures 5a and 5b report the typical Kurata-Stockmayer plot for atactic polybutene in decalin, toluene and benzene at 30°, and in decalin and tetralin at 100°. Only two trials were applied, as suggested by authors. (s) The values of K calculated in this way are also reported in Fig. 4: they appear to be in good agreement with those directly determined in 0 solvents.
~) BEN~TENEAT30°C
MV3
TOLUENE
I
2
""
"/
~
(~ TETRAI[N AT~00°C ~
] "~
I
. . ¢
I
I I
3
5
4
8
I ~ OEcAL'¢
2
. . . .
3
I
l
I
I I
I
4 5 6 ht ~/z$ . 10 3
Fzo. 5. (a) and (b). Treatment of viscosimetric data of fractions of atactic polybutene-1 in good solvents, according to Kurata-Stockmayer.(8)
It is to be noted that the temperature coefficient of the unperturbed dimensions of atactic polybutene-1 has already been evaluated a few years ago by thermoelastic measurements, which lead to the value of +0-48.10-3. <9) It appears obvious that the different ranges of temperature considered in this work and in that quoted elsewhere (9) may not affect the results as markedly. It must be concluded that the disagreement is due to the different methods used. The situation for atactic polybutene is, therefore, completely analogous to that for cistactic polybutadiene. For this polymer, viscosity measurements in 0 solvents on the one hand, (z°) and thermoelasticity determinations on the other,(lz) lead to temperature coefficients of unperturbed dimensions that differ both in value and in sign. This fact could be the consequence of different reliabilities of the two methods; we cannot, however, preclude the suggestion that the conformational behaviour of a polymer chain can, in fact, be different in bulk and in solution. In this connection, we may recall that something alike can be postulated also for the conformational parameter [(~02)/M]1/2. Recent experimental d a t a (12' 13) may be interpreted by the h y p o thesis of higher values for the molecular dimensions in bulk compared with those obtained from 0 solutions by viscosity and light scattering measurements.
Unperturbed Dimensions of Atactic Polybutene-I
257
REFERENCES (1) (2) (3) (4) (5)
(6) (7) (8) (9) (10) (11) (12) (13)
R. Chiang, Y. Phys. Chem. 70, 2348 (1966). G. Moraglio and G. Gianotti, Rc. 1st. lomb. Sci. Lett. A93, 683 (1959). V. Destenx and J. Bischoff, Bull. Soc. chim. Belg. 59, 93 (1950). G. Moraglio and G. Gianotti, Re. Accad. Naz. Lincei, 27 (8), 374 (1959). F. Dannsso, G. Moraglio and G. Gianotti, Pc. Ist. lomb. Sci. Lett. A94, 566 (1960). W. R. Krigbaum, J. E. Kurz and P. Smith, J. Phys. Chem. 65, 1984 (1961). G. Moraglio, Chimica Ind. Milano 44, 32 (1962). M. Kurata and W. Stockmayer, Fortsehr. HochpolymForsch. 3, 196 (1963). J. E. Mark and P. J. Flory, Y. Phys. Chem. 67, 1396 (1963). G. Moraslio, Europ. Polym. J. 1, 103 (1965). G. Crespi and U. Flisi, Makromolek. Chem. 60, 191 (1960). F. Bueche, B. J. Kinzig and C. J. Coven, Polym. Lett. B3, 399 (1965). W. R. Krigbaum and R. W. Godwin, J. Phys. Chem. 43, 4523 (1965).
On a d6termin6 les dimensions mol~'ulaires non perturb~es du poly-l-but~ne ~ partir de mesures viscosim6triques clans des solvants 0 darts l'intervalle de temp~'atures compris entre - 4 6 ° et +83 °. Desd~nni;essupp~i~aenta~ressur~esdimensi~nsn~n~p~rturbb:s~ca~cu~b~ajdede~appr~xi~ marion de Kurata--Stockmayer ~ partir d'~tudes dans des bons solvants, ont permis d'~tandre les r~ultats jusqu'b + 100% A partir de tousles r~sultats mesur~ et calcul~s on a obtenu ]e coefficient de temperature suivant: d l n r 6 x 103 = - 1 , 2 - - 0 , 2 dT On a compar~ cette valeur avec celle dbluite de mesures thermo~lastiques qui conduisent ~ un coefflcient positif. On discute les causes possibles de ce fait. Sommario--Si sono determinate le dimensioni imperturbate del polibutene-1 atattico mediante misure viscosimetriche in solventi 0, a temperatura comprese tra - 4 6 + • +83 °. Altri dati di dimensioni imperturbate, calcolati secondo la formulazione di Kurata-Stoclanayer da dati di soluzioni in buoni solventi, portano il campo di temperature esaminato free a + 100 °. Dal cornplesso dei daft si pub calcolare il co¢fficiente di temperatura: d l n ~ × 103 = _ 1.2_+~>2 dT +
Questo valore viene messo a confronto con quello ottenuto da misure termoelastiche, le quali danno un coefficiente positive: di questo fatto si discutono le possibili cause. ZmammendrA~mg----Die ungest6rten Dimensionen yon ataktischem Polybuten-I wurden durch viskosimetrische Messungen in 0-L6sungsmittein im Bereich zwischen - 4 6 ° und +83 ° bestimmt. Zusatzliche Daten tiber die ungest6nen Dimensionen, berechnet nach der N~therung yon KurataStockmayer aus Untersuchungen in guten L6sungsmitteln, sind geeignet, den Temperaturbereich bis zu I00 ° auszudehne . Ans allen berechneten und gemessenen Werten wird ffir den Temperaturkoeffizienten folgende Beziehung gefunden:
dlnr~-2
.I03ffi -1"2±0"2
Dieser Weft wird mit dem dutch thermoelastische Messungen erhaltenen verglichen, die ftir den Koeffizienten einen positiven Wert ergeben. Die m6glichen Ursachen fiir diesen Umstand werden diskutiert.
17
UNPERTURBED
MOLECULAR
POLYBUTENE-1
DIMENSIONS
AT DIFFERENT
OF ATACTIC
TEMPERATURES
G. MORAGHO, G. G t ~ o T r i and F. DANUSSO Istituto di Chimica Influstriale del Politecnico, Milano Centro Nazionale di Chimica delle Macromolecole del C.N.R. Sez. I, Milano
and Montecatini S.p.A. Milano (Received 28 November 1966) Abstract--The unperturbed dimensions of atactic polybutene-1 have been determined by viscosimetric measurements in 0 solvents over the range - 4 6 ° to +83 °. Additional data on unperturbed dimensions, calculated by the Kurata--Stockmayer approximation from studies of solutions in good solvents, are suitable to extend the range of temperature to 100 °. From all calculated and measured quantities, the following temperature coetf~ent is found: d In ~o.103ffi_ 1.2+0. 2 dT This value is compared with that obtained by thermoelastic measurements, which give a positive value for the ¢oemcient: the possible causes for this fact are discussed.
IN RECENTyears, particular attention has been devoted to the conformational parameter (d In r~/(dT), which measures the variation with temperature of the mean-square end-to-end distance of unperturbed molecular chains. This parameter appears in the theory of macromolecular solutions as well as in that of the thermoelastic properties of polymeric materials. Furthermore the temperature coefficient of the unperturbed dimensions has, in fact, wider implications than the dimensions themselves at a fixed temperature, if an accurate understanding of the confignrational and conformational properties of macromolecular chains is to be reached. For several polymers, unfortunately, the values of (d In ~)/(dT) quoted in the literature by different authors are in disagreement not only in value but also in sign. This is particularly the case for measurements in solutions for which more data are reported. •The use of particular theoretical treatments for solutions in good solvents might be one of the main reasons for scatter of the results. For these, values of thermodynamic parameters have frequently to be chosen in an arbitrary way. On the other hand, measurements in 0 solvents may not be free from criticism, if unperturbed dimensions are measured over too limited a range of temperature. It has often been stated that the different nature of the 0 solvents can determine the results. However, as proved in recent work for polyethylene,(1) this effect, if present, should be very small. We will assume that this conclusion is valid also for polybutene- 1, and in this paper we report data of unperturbed dimensions of the atactic isomer of this polymer, obtained by measurements in 0 solvents, over rather a wide range of temperature. 251
252
G. MORAGLIO, G. G I A N O T r l and F. DANUSSO
Some a d d i t i o n a l d a t a will be calculated, a c c o r d i n g to the K u r a t a - S t o c k m a y e r a p p r o x i m a t i o n , f r o m e x p e r i m e n t a l results in solutions in t h e r m o d y n a m i c a l l y favourable solvents; these last d a t a a p p e a r to be in a g r e e m e n t with the results directly o b t a i n e d in 0 solvents a n d further w i d e n the range o f t e m p e r a t u r e examined. EXPERIMENTAL
Samples andfractionation The polymeric samples were all prepared by polymerization with a catalyst derived from VCI( + aluminum diethylmonochloride, followed by ether extraction of the crude polymers.(2) The samples were purified by redissolution, followed by precipitation and drying; they possessed an X-ray crystallinity of only a few units per cent. A sample of polyhutene-1 thus obtained was further extracted at room temperature with a methanolbenzene mixture (13.5/86.5 by volume). The extracted sample, referred to as sample R, did not show any crystallinity by X-ray examination. The residue was further extracted by stirring with a methanol-chloroform mixture (17/83 by volume); the extracted polymer, referred to as sample RR, showed only traces of crystaUinity. Measurements of intrinsic viscosity in toluene at 30° gave, for the R and RR samples, 0.8 and 2 respectively (in 100 em3g--1). Two other samples of polybutene-1 were separately dissolved to give 0"5yo solutions in toluene, and the solutions were cooled to - 10° with stirring for about 6 hr; the soluble parts of the polymers were separated by sedimentation and further by centrifugation: they were precipitated with methanol. The polymers thus obtained are referred to as samples A and B. They showed traces of crystaLlinity by X-rays; their intrinsic viscosities at 30° were respectively 0.5 and 0-7 (in 100 cm3 g-l). Samples R, RR, A and B were fractionated by the usual techniques of fractional precipitation using toluene-methanol as solvent-non solvent pair. Further details of the techniques for the preparation of samples R and RR and for the subsequent fractionations can be found in a previous paper3 z) Solvents Solvents were dehydrated and distilled in a laboratory rectifying column. In particular, toluene for low temperature measurements was dried and rectified with metallic sodium. In all cases, solvents were protected from moisture by dehydrating agents. Viscosity measurements Desreux-Bischoff type viscometers were used.o) One of them was equipped with CaCI2 and P205 traps for low-temperature measurements. Critical temperatures of liquid phase separation They were determined by a suitable apparatus, fitted with a calibrated thermometer and CaC12 and P205 traps. Stirring was by means of a magnetic stirrer. RESULTS AND DISCUSSION I n a previous investigation o n the s o l u t i o n p r o p e r t i e s o f atactic polybutene-1, (4. 5) t w o d a t a were o b t a i n e d o f the u n p e r t u r b e d m o l e c u l a r dimensions in 0-solvents at t w o different temperatures. T h e [ ~ / ] = K M a relations were f o u n d to be [~/] = 11"33.10 - 4 M 0"5 in i s o a m y l a c e t a t e at 23 °
(1)
[7] = 10-51.10 - 4 M °'5 in phenetole a t 61 °
(2)
A first a p p r o x i m a t e value o f (d In r02)/(dT), f r o m (1) a n d (2), was - 1.3 x 10-3. T h e a i m o f the present w o r k is to widen the range o f t e m p e r a t u r e a n d t o refine t h a t deterruination, finding a d d i t i o n a l solvents b e l o w 23 ° a n d a b o v e 61 °. I n o r d e r to find a l o w t e m p e r a t u r e 0 solvent, the d a t a o b t a i n e d in a previous work, cs) interpreted a c c o r d i n g to the F o x - F l o r y t h e o r y o f solutions, suggested t h a t toluene
Unperturbed Dimensions of Atactic Polybutene-I
253
s h o u l d b e c o m e a p s e u d o - i d e a l solvent before r e a c h i n g its freezing point. T h e m o l e c u l a r weights o f several f r a c t i o n s o f s a m p l e s R, R R , A a n d B were m e a s u r e d viscometfically in t o l u e n e a t 30 ° using t h e p r e v i o u s l y stated f o r m u l a :(2.4) [7] = 1"55.10 -4 M 0'725
(3)
T h e values f o u n d are r e p o r t e d in the s e c o n d a n d t h i r d c o l u m n s o f T a b l e 1.* TABL~ 1. IN'rmNslc wsco~'t~s oF FRACTIONSOF ATACTICPOLYBUTENE-1IN TWO 0 SOLVENTSAND MOLECULAR V/EIGHTS CALCULATED BY INTRINSIC VISCOSITYIN TOLUENE AT 30 °(2) ([7] in 100 cm~ g-l)
['1] in toluene Fraction
RR 4222 R 322 R 4222 R 52 R 53 A 112 B 42 R 63 B 62
at 30 °t2)
M. 103
[7] in toluene at --46 °
[71 in anisole at 83 °
1.565 1.301 0.945 0"750 0.690 0.642 0.482 0-476 0.293
335 258 166 121 108 98"0 66.0 64"5 33-0
-0.674 0.540 0.470 0.444 --0"332 --
0.605 0.554 0.453 --0.350 0.274 0"278 0.190
T h e intrinsic viscosities o f s o m e fractions o f samples R a n d R R were then m e a s u r e d a t - 3 0 . 5 , - 3 5 a n d - 4 0 . 5 ° in t o l u e n e so t h a t the e x p o n e n t a o f the [ 7 ] - M r e l a t i o n for this solvent, at different t e m p e r a t u r e s , was d e t e r m i n e d . By e x t r a p o l a t i n g the values o f t e m p e r a t u r e f o r a ffi0.5, the 0 t e m p e r a t u r e f o r a t a c t i c p o l y b u t e n e in t o l u e n e was e s t i m a t e d as - 4 6 ° . A t the a b o v e l o w t e m p e r a t u r e s , the solutions o f the fractions o f s a m p l e s A a n d B show s o m e t u r b i d i t y due t o crystAlliT~tion o f isotactic s t e r e o b l o c k i m p u r i t i e s : the d a t a relating to these fractions in t o l u e n e at l o w t e m p e r a t u r e s have therefore been excluded. T h e n we m e a s u r e d [7] in t o l u e n e a t - 4 6 o f o r m o r e fractions o f s a m p l e R : the results are in t h e f o u r t h c o l u m n o f T a b l e I a n d are p l o t t e d a g a i n s t M in the d o u b l e l o g a r i t h m i c d i a g r a m o f Fig. 1. T h e following r e l a t i o n was d e r i v e d : [7] ffi 13-34.10 - 4 M °'s in toluene at - 4 6 °
(4)
W i t h r e g a r d to 0 solvents a b o v e 61 °, anisol was s h o w n to be a possible p s e u d o - i d e a l solvent. (6) * Samples of polybutene-1 undergo a moderate degradation with time: this causes values of [7] and M, reported in Table 1 and referring to fractions prepared some years ago, to be slightly lower than previously quoted. (2,4,5) The consequent higher polyclispersity of these fractions is thought to be inconsequential for our results.
254
G. MORAGLIO, G. G I A N O T F I and F. DANUSSO
For some fractions, obtained as above by fractional precipitation, the molecular weight was measured. The samples were dissolved in anisol (by heating at about I00 °) at different concentration near to the calculated critical composition, and the temperatures of liquid-liquid separation were determined by slowly cooling the solutions
ATACTIC POLY(BUTENE'1) IN TOLUENE AT - 4 6 °C
r,a
4,8 5.0 5,2 5.4 log I'I FIG, l. Intrinsic viscosities and molecular weights of fractions of atactic polybutene-1 in toluene at - 460: 0 conditions.
during stirring. From the state diagrams reported in Fig. 2a, the values of the critical temperature Tc were determined for the various fractions as the maximum value oftbe separation temperatures. Figure 2b reports T~-1 vs. the function x-I/2+ (2x)-l, x being the ratio between the molar volumes of the various fractions and of the solvent. The average straight line passing through the experimental points gives, by extrapolation, a 0 temperature of 83°.
==~z:. -
-
I Is-~0
2.95
\ 98"000
2.90
/
74 _~
/
66"000
68
~
86
2,85 33"000
/
2.8~
64 0
2
4
6
8
(2a)
10
/2 #
2
4
V=.tO
6
8
(_L.._LI.Io 2
~x" 2xl
(2b)
Fxo. 2. (a). Phase diagram for four fractions of atactic polybutene-1, of known molecular weight, in anisol. (b). Plot of Tc-1 vs. molecular size function [x-Z/z+(2x) -z] (x is the ratio between the molar volumes of polymer and of solvent).
Unperturbed Dimensions of Atactio Polybutene-1
255
The intrinsic viscosities of some fractions were then measured in anisol at 83 °. The values obtained are reported in the fifth column of Table 1, and the same data (Fig. 3) give the equation: [,7]= 10.81.10 -4 M °'5 in anisol at 83 ° (5)
t°~'I[~/]
ArACTIC POLY(BUTENE-1) IN ANISOL AT ,B3°C.
~8
4,6
4.8
5,0
5,2
5,4
log. N
F[o. 3. Intrinsic viscosities and molecular weights of fractions of atactic polybutene-I in anisol at 83°: Oconditions.
The values of log K relative to the various 0 solvents considered, are finally reported vs. temperature in Fig. 4 from which the following mean value can be calculated m
dlnr0: = 2 d l n K . . . . dT 3 dT
1-2.10 -3 (_+0-2.10-3 )
(6)
tog K E,tO ~,,I0 ~.0
-50 0 S0 I00 t °C FIG. 4. Plot of the unperturbed l~'ameter log K vs. temperature.
Although the measurements in 0 solvents should give more reliable values, we also determined some additional K values referring to unperturbed conditions from experimental data of [7] in good solvents, reported in previous papers (4, 7) by applying the Kurata-Stockmayer approximation. (s) This treatment has actually proved in many instances to give results of unperturbed dimensions largely independent of the solvent used, and in good agreement with those experimentally obtained with pseudo-ideal solvents. In addition, it can be applied without a previous choice of thermodynamic parameter values.
256
G. MORAGLIO, G. GIANOTTI and F. DANUSSO
Figures 5a and 5b report the typical Kurata-Stockmayer plot for atactic polybutene in decalin, toluene and benzene at 30°, and in decalin and tetralin at 100°. Only two trials were applied, as suggested by authors. (s) The values of K calculated in this way are also reported in Fig. 4: they appear to be in good agreement with those directly determined in 0 solvents.
~) BEN~TENEAT30°C
MV3
TOLUENE
I
2
""
"/
~
(~ TETRAI[N AT~00°C ~
] "~
I
. . ¢
I
I I
3
5
4
8
I ~ OEcAL'¢
2
. . . .
3
I
l
I
I I
I
4 5 6 ht ~/z$ . 10 3
Fzo. 5. (a) and (b). Treatment of viscosimetric data of fractions of atactic polybutene-1 in good solvents, according to Kurata-Stockmayer.(8)
It is to be noted that the temperature coefficient of the unperturbed dimensions of atactic polybutene-1 has already been evaluated a few years ago by thermoelastic measurements, which lead to the value of +0-48.10-3. <9) It appears obvious that the different ranges of temperature considered in this work and in that quoted elsewhere (9) may not affect the results as markedly. It must be concluded that the disagreement is due to the different methods used. The situation for atactic polybutene is, therefore, completely analogous to that for cistactic polybutadiene. For this polymer, viscosity measurements in 0 solvents on the one hand, (z°) and thermoelasticity determinations on the other,(lz) lead to temperature coefficients of unperturbed dimensions that differ both in value and in sign. This fact could be the consequence of different reliabilities of the two methods; we cannot, however, preclude the suggestion that the conformational behaviour of a polymer chain can, in fact, be different in bulk and in solution. In this connection, we may recall that something alike can be postulated also for the conformational parameter [(~02)/M]1/2. Recent experimental d a t a (12' 13) may be interpreted by the h y p o thesis of higher values for the molecular dimensions in bulk compared with those obtained from 0 solutions by viscosity and light scattering measurements.
Unperturbed Dimensions of Atactic Polybutene-I
257
REFERENCES (1) (2) (3) (4) (5)
(6) (7) (8) (9) (10) (11) (12) (13)
R. Chiang, Y. Phys. Chem. 70, 2348 (1966). G. Moraglio and G. Gianotti, Rc. 1st. lomb. Sci. Lett. A93, 683 (1959). V. Destenx and J. Bischoff, Bull. Soc. chim. Belg. 59, 93 (1950). G. Moraglio and G. Gianotti, Re. Accad. Naz. Lincei, 27 (8), 374 (1959). F. Dannsso, G. Moraglio and G. Gianotti, Pc. Ist. lomb. Sci. Lett. A94, 566 (1960). W. R. Krigbaum, J. E. Kurz and P. Smith, J. Phys. Chem. 65, 1984 (1961). G. Moraglio, Chimica Ind. Milano 44, 32 (1962). M. Kurata and W. Stockmayer, Fortsehr. HochpolymForsch. 3, 196 (1963). J. E. Mark and P. J. Flory, Y. Phys. Chem. 67, 1396 (1963). G. Moraslio, Europ. Polym. J. 1, 103 (1965). G. Crespi and U. Flisi, Makromolek. Chem. 60, 191 (1960). F. Bueche, B. J. Kinzig and C. J. Coven, Polym. Lett. B3, 399 (1965). W. R. Krigbaum and R. W. Godwin, J. Phys. Chem. 43, 4523 (1965).
On a d6termin6 les dimensions mol~'ulaires non perturb~es du poly-l-but~ne ~ partir de mesures viscosim6triques clans des solvants 0 darts l'intervalle de temp~'atures compris entre - 4 6 ° et +83 °. Desd~nni;essupp~i~aenta~ressur~esdimensi~nsn~n~p~rturbb:s~ca~cu~b~ajdede~appr~xi~ marion de Kurata--Stockmayer ~ partir d'~tudes dans des bons solvants, ont permis d'~tandre les r~ultats jusqu'b + 100% A partir de tousles r~sultats mesur~ et calcul~s on a obtenu ]e coefficient de temperature suivant: d l n r 6 x 103 = - 1 , 2 - - 0 , 2 dT On a compar~ cette valeur avec celle dbluite de mesures thermo~lastiques qui conduisent ~ un coefflcient positif. On discute les causes possibles de ce fait. Sommario--Si sono determinate le dimensioni imperturbate del polibutene-1 atattico mediante misure viscosimetriche in solventi 0, a temperatura comprese tra - 4 6 + • +83 °. Altri dati di dimensioni imperturbate, calcolati secondo la formulazione di Kurata-Stoclanayer da dati di soluzioni in buoni solventi, portano il campo di temperature esaminato free a + 100 °. Dal cornplesso dei daft si pub calcolare il co¢fficiente di temperatura: d l n ~ × 103 = _ 1.2_+~>2 dT +
Questo valore viene messo a confronto con quello ottenuto da misure termoelastiche, le quali danno un coefficiente positive: di questo fatto si discutono le possibili cause. ZmammendrA~mg----Die ungest6rten Dimensionen yon ataktischem Polybuten-I wurden durch viskosimetrische Messungen in 0-L6sungsmittein im Bereich zwischen - 4 6 ° und +83 ° bestimmt. Zusatzliche Daten tiber die ungest6nen Dimensionen, berechnet nach der N~therung yon KurataStockmayer aus Untersuchungen in guten L6sungsmitteln, sind geeignet, den Temperaturbereich bis zu I00 ° auszudehne . Ans allen berechneten und gemessenen Werten wird ffir den Temperaturkoeffizienten folgende Beziehung gefunden:
dlnr~-2
.I03ffi -1"2±0"2
Dieser Weft wird mit dem dutch thermoelastische Messungen erhaltenen verglichen, die ftir den Koeffizienten einen positiven Wert ergeben. Die m6glichen Ursachen fiir diesen Umstand werden diskutiert.
17