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Study of phase equilibrium by refractometry and the determination of second virial coefficients of polymer-plasticizer systems
:Polymer Science U.S.S.R. Vol. 24. ~o. 3, pp. 788-740, 1982 l~rlated in Poland
0032-3950/82/030738-03807.50[0 0 1983 Pergamon Pre~/.~td.
STUDY OF PHASE EQUILIBRIUM BY REFRACTOMETRY AND THE DETFRMINATION OF SECOND VIRIAL COEFFICIENTS OF POLYMER-PLASTICIZER SYSTEMS* A. A. TAO~R, S. A. VSHIVKOV and O. E. POLYAK A. M. Gor'ki State University, Urals
(Received 28 December 1980) I t was found possible to use refractometry for plotting phase diagrams of polymer--plasticizer systems when refractive indices of components are close and the cloud point method cannot be used. Second virial coefficients for the plasticized system were determined for the first time b y light scattering. ONE of the most effective methods of evaluating the thermodynamic eompatilibity of plasticizers and polymers is b y direct evaluation of their m u t u a l solubility in a wide range of temperature; phase diagrams, usually plotted applying the cloud point method (Alekseyev method), also provide information. This method cannot be used, however, if refractive indices of components are close. I t is therefore very important to find different methods for plotting phase diagrams of plasticized systems. The refractometrie method proposed b y Rehage [1] was used in this study for this purpose. A PS--eyclohexane (CH) model system was examined, the phase diagram of which is well known. A PMMA-tris-(2-ehloroethyl)phosphate system was also examined; refractive indices of its components n~ only differ b y 0.011 [2]. Second virial coefficients A 2 were determined for the first time on plasticized systems. A study was made of PS (31~r~----1.9×10 ~) a n d PMMA ( ~ / v = 4 . 8 × 10~). The plasticizer /--(tris-(2-chloroethyl)phosphate (TECP)--is a liquid of boiling point 173 ° C a n d a density p ~ 0 . 9 2 2 0 g/era [2], which was provided b y the V.A. Kargin I n s t i t u t e of Chemistry and Polyaner Technology. Solutions with a gravimetric proportion of the polymer ~os~0.25 were prepared in ampoules in a few days at 70 ° (PS-CH) a n d 120 ° (PMMA-TECP). Concent r a t e d (e0~0-25) PMMA solutions were prepared in the form of films. Toluene solutions previously prepared of PMMA and TECP in given ratios were then applied on a cellophane substrate. Transparent mixtures were kept at 40-50 ° for a few days u n t i l the toluene had completely evaporated. Film thickness was 0-3-0-5 mm. To determine the refractive index n D, a solution drop or film was placed between prisms of an I R F - 2 2 refractometer; temperature was changed at a rate of 5 deg/hr. The accuracy of thermostatic control of solutions (fihns) was ~: 0.1 °. Second virial coefficients were determined by light scattering. For this purpose dust ~vas removed from PMMA solutions in the plasticizer and from the plasticizer by filtration u n d e r a pressure of ~ 2 arm through a Teflon fabric with pore size 1-3/tin. Light seatfering of solutions was measured b y a photoelectric nephelometer. An LG-75-I helium-neon laser of wave length 632.8 ran was the light source. The light scattered b y the solution was recorded using a FEU-28 photo-multiplier. The refractive index increment was determined using a n IFR-23 interference refractometer. An LG-56 laser with a wave length 2 = 632.8 n m was used as light source.
* Vysokomol. soyed. A24: No. 3, 661-663, I982. 738
D e t e r m i n a t i o n of sedond virial coefficients of p o l y m e r - p l a s t i c i z e r systems
739
The application of the refractometric method for plotting phase diagrams. T h e m e t h o d i n v o l v e s d e t e r m i n a t i o n of t h e t e m p e r a t u r e d e p e n d e n c e of t h e r e f r a c t i v e i n d e x of p o l y m e r solutions of different concentrations. These dependences are different in h o m o g e n e o u s a n d h e t e r o g e n e o u s ranges a n d curves n ~ f ( T ) show breaks, t e m p e r a t u r e s of which correspond to t e m p e r a t u r e s of phase s e p a r a t i o n Tp.s. I t is k n o w n t h a t f r o m t h e t e m p e r a t u r e d e p e n d e n c e of coefficients of refraction T~ values of p o l y m e r s are d e t e r m i n e d . Therefore, T~.s. of pla,~ticized systems can o n l y be d e t e r m i n e d b y this m e t h o d if T > T~.
n %
a
1.476
b
no2I
l'~ - ~ ~ 3 "3 I'45, I I 3O 5O Az'lO~cmZmWe/g2
1"4a
q
I 7O7"~
TO
I"45
I
m
I ~Z 3O
° 7TM
Fio. 1
O.Z
0.6
oJz
Fro. 2
FIG. 1. T e m p e r a t u r e d e p e n d e n c e of t h e r e f r a c t i v e i n d e x of (a) P S - C t t , P M M A - T E C P (b) s y s t e m s for solntion c o n c e n t r a t i o n s of 12.8 (1), 28.2 (2), 20 (3), 3 7 % (4) a n d (c) of the s e c o n d virial coefficient of t h e P M M A - T E C P system. FIG. 2. C o n c e n t r a t i o n dependence of Tp.s. of t h e P M M A - T E C P system. I n order to confirm t h a t t e m p e r a t u r e s of points of discontinuities o b s e r v e d on c u r v e s
n = f ( T ) do, in fact, coincide w i t h Tp.s., we used PS solutions in C H as m o d e l systems. }¢esulr, s o b t a i n e d were c o m p a r e d w i t h Tp.s. d e t e r m i n e d using t h e cloud p o i n t m e t h o d . F i g u r e la shows t h e d e p e n d e n c e of nD=f(T ) for PS solutions of two concentratic, ns. Tp.s. of these solutions d e t e r m i n e d f r o m t h e points of intersection of s t r a i g h t lines (,vith ~m a c c u r a c y of up to 0.2 °) coincides w i t h Tp.s. d e t e r m i n e d f r o m cloud points. Conse(tuent.ly, the r e f r a c t o m e t r i c m e t h o d enables a c c u r a t e values of Tp.~. to be obtained. F i g u r e lb shows t h e dependence of n s = f (T) for P M M A solutions in T E C P a n d Fig. 2, t h e phase d i a g r a m of this system. I t can be seen t h a t t h e P M M A - T E C P s y s t e m ].,as an u p p e r critical solution t e m p e r a t u r e which is 4 5 ± 1°. P M M A solutions w i t h a c o n c e n t r a t i o n of 09~<0.65 in t h e t e m p e r a t u r e range e x a m i n e d are in the high-elastic a n d plastic states a n d those w i t h a c o n c e n t r a t i o n co~> 0-65-- in t h e glassy state. A b o v e t h e binodal t h e syst,+m is h o m o g e n e o u s a n d below t h e binodal, gels are formed, which is n o t a c c o m p a n i e d by cloud f o r m a t i o n since t h e refractive indices are similar. Second virial coefficients of the P M M A - T E C P system.. L i g h t scattering of P M M A solutio ns was studied at an angle of scattering 0 ~ 9 0 ° a n d results were a n a l y s e d using the D e h y e m e t h o d [d]. The t e m p e r a t u r e dependence of A2 values calculated is shown in Fig. lc. I t <,~u be seen t h a t on reducing t e m p e r a t u r e , A2 v a l u e s decrease a n d a t a t e m p e r a t u r e lower t h a n 44 ° t h e y b e c o m e n e g a t i v e . Therefore, on r e d u c i n g t e m p e r a t u r e , t h e t h e r m o d s m a m i e a f f i n i t y o f P M M A w i t h T E C P decreases, w h i c h results in phase s e p a r a t i o n of t h e system. Tranalated by E. SEMERE
740
H e r m a n Staudinger (1881-1965) AEE~HNC~$
I. G. REHAGE, Kunststoffen 53; 1~o. 9, 603, 1963 2. I. N. R A Z I N S K A Y A , V. A . A G E Y E V A , N. I. Y E R M I L I N A , L K . R Y B T S O V A a n d B. P.
SHTARKMAN, Plast. massy, No. 1, 27, 1977 3. A. A. TAGER, Fizikokhimiya polimerov, p. 544, 3-ye izd. Khimiya, Moscow
Polymer Science U.S.S.R. Vol. 24. ~o. 3, pp. 740-742,1982 Printed in Poland
0032.3950/82/080740-03507.50/0 1988 Pergamon Press Ltd.
PERSONALITIES HERMANN STAUDINGER (1881-1965) (100th anniversary of his birth) IT WAS 100 years ago in 1981 t h a t Prof. H. S t a n d i n g e r - - o n e of the founders of polymer science a n d BTobel prize winner--was born. H. Staudinger's biography is a classical example of a university scientist of the end of the X I X century and of the first half of the X X cent. First he studied in Darmstadt at Prof. Kolbe a n d then at A. yon Bayer a n d Piloti in Mfinich a n d completed his university education in Galle, where under the guidance of Prof. Farlander he obtained in 1903 his thesis entitled "Addition of Malonic Ester to U n s a t u r a t e d Compounds". F r o m 1903 to 1907 H. Staudinger was Assistant to Prof. Thiele in Strasbourg, where he prepared the first ketene -- diphenylketene a n d his study in the field of ketenes was submitted in 1907 for a competition for a Doctorate in Sciences. I n the same year (1907) already as a recognized scientist. H. Staudinger was appointed Professor a d j u n c t a t the University of Karlsruhe a n d in 1912--Professor of the Technical U n i v e r s i t y in Zf~ich. T h e period of activity of H. Staudinger at the technical university fl'om 1912 to 1926 m a y be called the pioneer period of polymer science. During this period he continued classical research into ketene chemistry a n d in 1920 he started investigations into high-molecular weight compounds. I n 1926 Prof. H. Staudinger commenced a long period of studies at Freiburg University, where in 1951 he founded a n d became head of the Institute of Macromolecular Chemistry. I n 1956 at the age of 75 Prof. H. Staudinger retired, b u t continued u n t i l 1965 to supervise t h e publication of the journal Die Makromolekulare Chemie, which he founded in 1944. When in 1920 H. Staudinger started investigations into the formation a n d structure ~)f polymers, this was a n a t u r a l step prepared by m a n y years' s t u d y in the field of ketenes. I t was still in 1911 in Karlsruhe that he developed with C. Clever a simple method for pre. paring isoprene b y pyrolysis of dipentene a n d investigated its polymerization. During this period (1912) together with L. Lautenschlager he found t h a t peroxides, particularly dibenzoylperoxide, initiate polymerization of styrene and other unsaturated compounds. Still in Karlsruhe H. Staudinger prepared a synthetic rubber b y polymerization of isoprene. Differences in its properties a n d those of n a t u r a l rubber induced him to examine in •nore detail processes of polymerization, including the formation of polyoxymethylene, * V y s o k o m o l . s o y e d . A24: N o . 3, 6 6 4 - 6 6 5 , 1982.
0032-3950/82/030738-03807.50[0 0 1983 Pergamon Pre~/.~td.
STUDY OF PHASE EQUILIBRIUM BY REFRACTOMETRY AND THE DETFRMINATION OF SECOND VIRIAL COEFFICIENTS OF POLYMER-PLASTICIZER SYSTEMS* A. A. TAO~R, S. A. VSHIVKOV and O. E. POLYAK A. M. Gor'ki State University, Urals
(Received 28 December 1980) I t was found possible to use refractometry for plotting phase diagrams of polymer--plasticizer systems when refractive indices of components are close and the cloud point method cannot be used. Second virial coefficients for the plasticized system were determined for the first time b y light scattering. ONE of the most effective methods of evaluating the thermodynamic eompatilibity of plasticizers and polymers is b y direct evaluation of their m u t u a l solubility in a wide range of temperature; phase diagrams, usually plotted applying the cloud point method (Alekseyev method), also provide information. This method cannot be used, however, if refractive indices of components are close. I t is therefore very important to find different methods for plotting phase diagrams of plasticized systems. The refractometrie method proposed b y Rehage [1] was used in this study for this purpose. A PS--eyclohexane (CH) model system was examined, the phase diagram of which is well known. A PMMA-tris-(2-ehloroethyl)phosphate system was also examined; refractive indices of its components n~ only differ b y 0.011 [2]. Second virial coefficients A 2 were determined for the first time on plasticized systems. A study was made of PS (31~r~----1.9×10 ~) a n d PMMA ( ~ / v = 4 . 8 × 10~). The plasticizer /--(tris-(2-chloroethyl)phosphate (TECP)--is a liquid of boiling point 173 ° C a n d a density p ~ 0 . 9 2 2 0 g/era [2], which was provided b y the V.A. Kargin I n s t i t u t e of Chemistry and Polyaner Technology. Solutions with a gravimetric proportion of the polymer ~os~0.25 were prepared in ampoules in a few days at 70 ° (PS-CH) a n d 120 ° (PMMA-TECP). Concent r a t e d (e0~0-25) PMMA solutions were prepared in the form of films. Toluene solutions previously prepared of PMMA and TECP in given ratios were then applied on a cellophane substrate. Transparent mixtures were kept at 40-50 ° for a few days u n t i l the toluene had completely evaporated. Film thickness was 0-3-0-5 mm. To determine the refractive index n D, a solution drop or film was placed between prisms of an I R F - 2 2 refractometer; temperature was changed at a rate of 5 deg/hr. The accuracy of thermostatic control of solutions (fihns) was ~: 0.1 °. Second virial coefficients were determined by light scattering. For this purpose dust ~vas removed from PMMA solutions in the plasticizer and from the plasticizer by filtration u n d e r a pressure of ~ 2 arm through a Teflon fabric with pore size 1-3/tin. Light seatfering of solutions was measured b y a photoelectric nephelometer. An LG-75-I helium-neon laser of wave length 632.8 ran was the light source. The light scattered b y the solution was recorded using a FEU-28 photo-multiplier. The refractive index increment was determined using a n IFR-23 interference refractometer. An LG-56 laser with a wave length 2 = 632.8 n m was used as light source.
* Vysokomol. soyed. A24: No. 3, 661-663, I982. 738
D e t e r m i n a t i o n of sedond virial coefficients of p o l y m e r - p l a s t i c i z e r systems
739
The application of the refractometric method for plotting phase diagrams. T h e m e t h o d i n v o l v e s d e t e r m i n a t i o n of t h e t e m p e r a t u r e d e p e n d e n c e of t h e r e f r a c t i v e i n d e x of p o l y m e r solutions of different concentrations. These dependences are different in h o m o g e n e o u s a n d h e t e r o g e n e o u s ranges a n d curves n ~ f ( T ) show breaks, t e m p e r a t u r e s of which correspond to t e m p e r a t u r e s of phase s e p a r a t i o n Tp.s. I t is k n o w n t h a t f r o m t h e t e m p e r a t u r e d e p e n d e n c e of coefficients of refraction T~ values of p o l y m e r s are d e t e r m i n e d . Therefore, T~.s. of pla,~ticized systems can o n l y be d e t e r m i n e d b y this m e t h o d if T > T~.
n %
a
1.476
b
no2I
l'~ - ~ ~ 3 "3 I'45, I I 3O 5O Az'lO~cmZmWe/g2
1"4a
q
I 7O7"~
TO
I"45
I
m
I ~Z 3O
° 7TM
Fio. 1
O.Z
0.6
oJz
Fro. 2
FIG. 1. T e m p e r a t u r e d e p e n d e n c e of t h e r e f r a c t i v e i n d e x of (a) P S - C t t , P M M A - T E C P (b) s y s t e m s for solntion c o n c e n t r a t i o n s of 12.8 (1), 28.2 (2), 20 (3), 3 7 % (4) a n d (c) of the s e c o n d virial coefficient of t h e P M M A - T E C P system. FIG. 2. C o n c e n t r a t i o n dependence of Tp.s. of t h e P M M A - T E C P system. I n order to confirm t h a t t e m p e r a t u r e s of points of discontinuities o b s e r v e d on c u r v e s
n = f ( T ) do, in fact, coincide w i t h Tp.s., we used PS solutions in C H as m o d e l systems. }¢esulr, s o b t a i n e d were c o m p a r e d w i t h Tp.s. d e t e r m i n e d using t h e cloud p o i n t m e t h o d . F i g u r e la shows t h e d e p e n d e n c e of nD=f(T ) for PS solutions of two concentratic, ns. Tp.s. of these solutions d e t e r m i n e d f r o m t h e points of intersection of s t r a i g h t lines (,vith ~m a c c u r a c y of up to 0.2 °) coincides w i t h Tp.s. d e t e r m i n e d f r o m cloud points. Conse(tuent.ly, the r e f r a c t o m e t r i c m e t h o d enables a c c u r a t e values of Tp.~. to be obtained. F i g u r e lb shows t h e dependence of n s = f (T) for P M M A solutions in T E C P a n d Fig. 2, t h e phase d i a g r a m of this system. I t can be seen t h a t t h e P M M A - T E C P s y s t e m ].,as an u p p e r critical solution t e m p e r a t u r e which is 4 5 ± 1°. P M M A solutions w i t h a c o n c e n t r a t i o n of 09~<0.65 in t h e t e m p e r a t u r e range e x a m i n e d are in the high-elastic a n d plastic states a n d those w i t h a c o n c e n t r a t i o n co~> 0-65-- in t h e glassy state. A b o v e t h e binodal t h e syst,+m is h o m o g e n e o u s a n d below t h e binodal, gels are formed, which is n o t a c c o m p a n i e d by cloud f o r m a t i o n since t h e refractive indices are similar. Second virial coefficients of the P M M A - T E C P system.. L i g h t scattering of P M M A solutio ns was studied at an angle of scattering 0 ~ 9 0 ° a n d results were a n a l y s e d using the D e h y e m e t h o d [d]. The t e m p e r a t u r e dependence of A2 values calculated is shown in Fig. lc. I t <,~u be seen t h a t on reducing t e m p e r a t u r e , A2 v a l u e s decrease a n d a t a t e m p e r a t u r e lower t h a n 44 ° t h e y b e c o m e n e g a t i v e . Therefore, on r e d u c i n g t e m p e r a t u r e , t h e t h e r m o d s m a m i e a f f i n i t y o f P M M A w i t h T E C P decreases, w h i c h results in phase s e p a r a t i o n of t h e system. Tranalated by E. SEMERE
740
H e r m a n Staudinger (1881-1965) AEE~HNC~$
I. G. REHAGE, Kunststoffen 53; 1~o. 9, 603, 1963 2. I. N. R A Z I N S K A Y A , V. A . A G E Y E V A , N. I. Y E R M I L I N A , L K . R Y B T S O V A a n d B. P.
SHTARKMAN, Plast. massy, No. 1, 27, 1977 3. A. A. TAGER, Fizikokhimiya polimerov, p. 544, 3-ye izd. Khimiya, Moscow
Polymer Science U.S.S.R. Vol. 24. ~o. 3, pp. 740-742,1982 Printed in Poland
0032.3950/82/080740-03507.50/0 1988 Pergamon Press Ltd.
PERSONALITIES HERMANN STAUDINGER (1881-1965) (100th anniversary of his birth) IT WAS 100 years ago in 1981 t h a t Prof. H. S t a n d i n g e r - - o n e of the founders of polymer science a n d BTobel prize winner--was born. H. Staudinger's biography is a classical example of a university scientist of the end of the X I X century and of the first half of the X X cent. First he studied in Darmstadt at Prof. Kolbe a n d then at A. yon Bayer a n d Piloti in Mfinich a n d completed his university education in Galle, where under the guidance of Prof. Farlander he obtained in 1903 his thesis entitled "Addition of Malonic Ester to U n s a t u r a t e d Compounds". F r o m 1903 to 1907 H. Staudinger was Assistant to Prof. Thiele in Strasbourg, where he prepared the first ketene -- diphenylketene a n d his study in the field of ketenes was submitted in 1907 for a competition for a Doctorate in Sciences. I n the same year (1907) already as a recognized scientist. H. Staudinger was appointed Professor a d j u n c t a t the University of Karlsruhe a n d in 1912--Professor of the Technical U n i v e r s i t y in Zf~ich. T h e period of activity of H. Staudinger at the technical university fl'om 1912 to 1926 m a y be called the pioneer period of polymer science. During this period he continued classical research into ketene chemistry a n d in 1920 he started investigations into high-molecular weight compounds. I n 1926 Prof. H. Staudinger commenced a long period of studies at Freiburg University, where in 1951 he founded a n d became head of the Institute of Macromolecular Chemistry. I n 1956 at the age of 75 Prof. H. Staudinger retired, b u t continued u n t i l 1965 to supervise t h e publication of the journal Die Makromolekulare Chemie, which he founded in 1944. When in 1920 H. Staudinger started investigations into the formation a n d structure ~)f polymers, this was a n a t u r a l step prepared by m a n y years' s t u d y in the field of ketenes. I t was still in 1911 in Karlsruhe that he developed with C. Clever a simple method for pre. paring isoprene b y pyrolysis of dipentene a n d investigated its polymerization. During this period (1912) together with L. Lautenschlager he found t h a t peroxides, particularly dibenzoylperoxide, initiate polymerization of styrene and other unsaturated compounds. Still in Karlsruhe H. Staudinger prepared a synthetic rubber b y polymerization of isoprene. Differences in its properties a n d those of n a t u r a l rubber induced him to examine in •nore detail processes of polymerization, including the formation of polyoxymethylene, * V y s o k o m o l . s o y e d . A24: N o . 3, 6 6 4 - 6 6 5 , 1982.