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Use of gel permeation chromatography to determine the molecular weight distribution of secondary cellulose acetates
USE OF GEL PERMEATION CHROMATOGRAPHY TO DETERMINE THE MOLECULAR WEIGHT DISTRIBUTION OF SECONDARY CELLULOSE ACETATES* P . A. OKUI~'EV, C. P . DOROFEYEV, Z. A . KUDRYAVTSEVA~ a n d O. G. TARAKA~OV Vladimir Polytechnic
(Received 20 January 1970) GEL permeation chromatography (GPC) is used to investigate molecular weight distribution (MWD) of polymers. The term "gel permeation chromatography" was introduced by Moor [1]. GPC is based on the varying abi]iity of molecules to permeate particles of a swollen polymeric crosslinked gel. Large molecules permeate gel particles to a lesser extent and
/1.
Fro. 1. Column used for gel permeation chromatography: / - - g l a s s tube containing the gel, 2--special tap, 3--vessel containing eluent, 4--siphon, 5 - - t e s t tube. during elution are the first to emerge from the column. Smaller molecules more readily permeate the gel particles and remain in the column for a longer time. Thus, molecules become distributed according to dimensions when passing the polymer solution through the column. Substances with molecular weights ranging from several hundreds to several millions can be analysed b y GPC. Various gels m a y be used. A comparison is made in the s t u d y [2] of the efficiency of separating molecules according to size on various porous materials. Crosslinked polystyrene gels [1-17] are most widely used. * Vysokomol. soyed. A18: No. 7, 1680--1683, 1971. 1893
1894
P.A.
Oxu:~v
et al.
~n
6O
20 I
30
/vO
50 V, nom.un.
60
Fig. 2. Elution curves of acetylcellulose fractions using a column 2 m in length. S o l v e n t - - T H F . Fractions with molecular weight 270,000 (1), 104,000 (2) 58,000 (3) and 11,000 (4). The effects of the concentration and a m o u n t of p o l y m e r introduced in the column, column temperature, rat~ of elution, length of column, various solvents on the accuracy of determining 1KWD of the polymer were examined in former papers [4, 5, 9, 10]. M W I ) determined b y GPC coincides satisfactorily with M W I ) determined b y other methods [7, 8]. The columns are normally calibrated with polymers of narrow M W D [1, 5, 16].
cl
./if?
80
2
60 ~0 2O
35
05
55
65
OO
50
60
70
V,/7om.un.
1~I~. 3. Elution curves of acetylcellulose fractions using a column 2 (a) a n d 3 m (b) in length. Solvent--acetone.
~ogn
5 " 5 ~ 5"0
3
0"0 I
O0
1
50
V, nom.un.
6g
/~zG. 4. Calibration curves for columns o f different lengths: 1 - - 2 m, s o l v e n t - - T H F ;
2 - - 2 m, acetone; 3 - - 3 m, acetone.
1895
Use of gel permeation chromatography
Studies of the theoretical and experimental problems o f GPC are reviewed in a separate paper [12]. A report is made [13, 17] of the use of GPC for the study of MWD of cellulose and its nitroesters. The authors of these studies point to the advantages of this m e t h o d of investigation over methods of fractional precipitation and solution [18-20]. An
2O
3O
O0
50
60
V ~ nom. un.
FIo. 5. Elution curves of unfractionated acetylcellulose samples using a column 2 m in length. S o lv e n t- - a c e to n e . SCA with a specific viscosity of 0.29 (1), 0.53 (2, 2'); first analysis (2), repeated analysis (2'). First, the method enables the polymer sample to be analysed in a few hours, while the methods mentioned previously require several days. Second, by selecting a column, the curve of lVIWD of the polymer can be increased in resolving power in the range of molecular weights in question. Third, GPC enables us to obtain not only weight-average an d number-average molecular weights and MWD, b u t also information concerning the degree of association in sohition. Fourth, differential curves of distribution are plotted directly from results of measurements in the apparatus. An a t t e m p t was made in this study to use GPC to determine the MW D of secondary cellulose acetates.
EXPERIMENTAL Chromatographic cohmms were filled with a erosslinked polystyrene gel of requisite porosity. Gels were obtained b y copolymerization of styrene and divinylbenzene. The column (Fig. 1) is a glass tube of about 10 m m in diameter and 2 or 3 m in length, which is uniformly filled with gel. 10 mg polymer in 1~/o solution was added to the upper part of the column. The polymer was then elated from the column with a solvent at a rate of 0.4 ml/lrdn. To plot the elation curve of the polymer, samples of 2.4 ml each were taken using a pipette-siphon. Polymer concentrations were determined in each of these samples using an ITR-1 interferometer. F r o m the result an ehition curve was plotted in coordinates V-An, where V is the eluent volume in nominal units (one nominal unit is 2.4 ml), An is the variation of the refractive index of the eluent in units of the scale of the I TR- 1 device. The column was calibrated with secondary cellulose acetate (SCA) fractions with molecular weights 270,000, 104,000, 58,000 and 11,000 obtained by fractional precipitation. T e t r a hydrofuran (TI-IF) and acetone were used as eluents and solvents for SCA.
RESU LTS T H F was used as solvent for SCA and eluent. Figure 2 shows that the thition volume~ v a r y for SCA fractions. F o r polymers with molecular weights of 270,000, 104,000, 58,00(~ and 11,000 the elation volumes were 35-5; 37.6; 40.2; 48.7 nora. units, respectively. These volumes were determined from the peak of the elation curve. T H F is the most 'extensively used solvent in GPC. This solvent, however, is not ideal. First, it is very subject to oxidation and consequently, to variation of refractive index.
1896
P. At. O ~ : ~ . v
et al.
T h i s n o r m a l l y causes a c h a n g e , or d i s p l a c e m e n t in t h e zero line o f t h e c u r v e , w h i c h is u n d e s i r able. A c e t o n e is a m o r e s t a b l e s o l v e n t f r o m t h i s a s p e c t a n d dissolves m a n y p o l y m e r s , i n c l u d i n g also SCA. I n a d d i t i o n , for a c e t o n e t h e r e f r a c t i v e i n d e x is lower t h a n for T H F , w h i c h increases t h e s e n s i t i v i t y of GPC. T h i s is v e r y i m p o r t a n t if t h e I T R - 1 d e v i c e is u s e d t o d e t e r m i n e t h e difference in r e f r a c t i v e indices. I n o r d e r t o use a c e t o n e , we t e s t e d gels, w h i c h were i n t e n d e d for o b t a i n i n g c l u t i o n c u r v e s b y G P C in TI-IF. I t a p p e a r e d t h a t gels w h i c h p r o v e d s a t i s f a c t o r y in f r a c t i o n a t i o n o f SCAt in T H F axe u n s a t i s f a c t o r y for use in a c e t o n e , since in a c e t o n e gel swells Jess s a t i s f a c t o r i l y t h a n in T H F . Therefore, t o use a c e t o n e in G P C of s e c o n d a r y a c e t a t e s , similar gels s u b j e c t e d t o special t r e a t m e n t were t a k e n . E x p e r i m e n t s s h o w (Fig. 3a) t h a t o n u s i n g a c e t o n e t h e s a m e efficiency c a n be o b t a i n e d in t h e s e p a r a t i o n o f m a c r o m o l e c u l e s as w h e n u s i n g T H F . F i g u r e 3a i n d i c a t e s t h a t for SCAt s a m p l e s f r a c t i o n a t e d in T H F (Fig. 2) r e s p e c t i v e e l u t i o n v o l u m e s o f a c e t o n e were 37.0; 39.1; 41.1; a n d 52.0 h e m . un. (curves 1-4, r e s p e c t i v e l y ) . F i g u r e 3b s h o w s e l u t i o n c u r v e s w i t h a c e t o n e o f SCAt f r a c t i o n s in a c o l u m n 3 m in l e n g t h a n d 8.5 m m in d i a m e t e r . T h e s e p a r a t i o n o f m o l e c u l e s a c c o r d i n g to d i m e n s i o n is m o r e satisf a c t o r y in t h i s case t h a n in 2 - m e t r e c o l u m n s . E l u t i o n v o l u m e s for SCAt f r a c t i o n s u s e d b y t h e a u t h o r s were 38.3; 42.6; 47.3; 57.6 nora. un. (curves 1-4, r e s p e c t i v e l y ) in o r d e r of decreasing m o l e c u l a r weights. Comparing results obtained using three- and two-meter columns it may be concluded t h a t t h e r e s o l v i n g p o w e r of t h e c o l u m n increases w i t h a n i n c r e a s e i n l e n g t h . H o w e v e r , t h e d u r a t i o n o f a n a l y s i s also increases p r o p o r t i o n a t e l y . F r a c t i o n a t i o n t i m e i n a 2 - m e t r e c o l u m n was a b o u t 5 hr, in a 3 - m e t r e c o l u m n , 8 hr. F r o m e l u t i o n v o l u m e s for e a c h o f t h e c o l u m n s c a l i b r a t i o n c u r v e s were p l o t t e d (Fig. 4) in c o o r d i n a t e s V - l o g d~l, w h e r e M is m o l e c u l a r weight, V is e l u t i o n v o l u m e . As s h o w n b y t h e s e c u r v e s a 3 - m e t r e c o l u m n is m o r e effective since t h e g r a d i e n t o f t h e c a l i b r a t i o n c u r v e is smaller. T h e c u r v e is a l m o s t a s t r a i g h t line, w h i c h is m o r e c o n v e n i e n t for c a l c u l a t i o n . F i g u r e 5 s h o w s e l u t i o n c u r v e s of u n f r a c t i o n a t e d SCAt aamples p r e p a r e d f r o m c o t t o n cellulose w i t h a specific v i s c o s i t y of a 0"25~oo s o l u t i o n in a c e t o n e of 0-53 a n d w o o d cellulose w i t h a specific v i s c o s i t y o f t h e s a m e s o l u t i o n o f 0-29. As s h o w n b y t h e Figure, u n f r a c t i o n a t e d s a m p l e s are d i s t r i b u t e d o v e r t h e whole r a n g e o f c a l i b r a t i o n . F i g u r e 5 also s h o w s r e s u l t s of r e p e a t e d e l u t i o n o f a s a m p l e w i t h a specific v i s c o s i t y o f 0-53 in t h e s a m e c o l u m n . T h e F i g u r e shows s a t i s f a c t o r y a g r e e m e n t b e t w e e n b o t h results. I t is t h u s s h o w n t h a t M W D of s e c o n d a r y cellulose a c e t a t e s c a n f a i r l y q u i c k l y a n d a c c u r a t e l y be d e t e r m i n e d b y GPC. I n c o n t r a s t t o classical m e t h o d s o f f r a c t i o n a t i o n (by f r a c t i o n a l s o l u t i o n a n d p r e c i p i t a t i o n ) , t h i s m e t h o d e n a b l e s us to d e t e r m i n e t h e a c t u a l M W D o f cellulose a c e t a t e s , since s e p a r a t i o n b y t h i s m e t h o d o n l y t a k e s place a c c o r d i n g t o m o l e c u l a r d i m e n s i o n a n d n o t a c c o r d i n g to t h e difference in solubility, w h e r e c h e m i c a l h e t e r o g e n e i t y of p o l y m e r c h a i n s h a s a n effect.
CONCLUSIONS At r a p i d m e t h o d was d e v e l o p e d for d e t e r m i n i n g t h e m o l e c u l a r w e i g h t d i s t r i b u t i o n o f s e c o n d a r y cellulose a c e t a t e s b y gel p e r m e a t i o n c h r o m a t o g r a p h y .
Translated by E. SEM~RE
REFERENCES l. 2. 3. 4. 5.
J. M. N. K. J.
C. MOORE, J . P o l y m e r Sci. A2: 835, 1964 F. V A U G I t A N , N a t u r e 195: 801, 1962 SCHNEIDER, J . P o l y m e r Sci. C8: 179, 1965 A. BONI, F. A. S L I E M E R Z a n d P. B. STICKNEY, J . P o l y m e r Sci. 6: A-2: 1567, 1968 C. M O O R E a n d J. C. I-IENDRICKSON, J . P o l y m e r Scl. {38: 233, 1965
Determining Flory-l=[uggins reaction parameter 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.
1897
J. C. HENDRICKSON, J . Appl. Polymer Sci. 11: 1419, 1967 L. E. MALEY, J. Polymer Sci. C8: 253, 1965 M. J. R. CANTOW, R. S. PORTER and J. E. JOHNSON, J. Polymer Sei. C16: 13, 1967 M. J. R. CANTOW, R. S. PORTER and J. F. JOHNSON, J. Polymer Sei. B4: 707, 1966 M. J. R. CANTOW, R. S. PORTER and J. F. JOHNSON, J. Polymer Sci. 5: A - l : 987, 1967 C. L. ROHN, J. Polymer Sci. 5: A-2, 547, 1967 Novoye v metodakh issledovaniya polimerov (New Methods of Investigations). Izd. "Mir", 1968 T. E. MULLER and W. J. ALEXANDER, $. Polymer Sci. C21: 283, 1968 D. J. HARMON, J, Polymer Sci. C8: 243, 1965 J. H. DUERKSEN and A. E. A M I E L E S , J. Polymer Sci. C21: 83, 1968 H. W. OSTERHOUDT and L. N. RAY, J. Polymer Sei. 5, A-2: 569, 1967 L. SEGAL, J . Polymer Sci. C21: 267, 1968 O. G. TARAKANOV, P. A. OKUNEV, Vysokomol. soyed. 4: 683, 1962 (Not t r a n s l a t e d in Polymer Sci. U.S.S.R.) P. A. OKUNEV and O. G. TARAKANOV, Khimich. volokna, No. 6, 44, 1963 STAN' ZHEN'-YUAN', Opredelenie molekulyarnykh vesov polimerov (Determining Polymer Molecular Weight). Izd. inostr, lit., 1962
DETERMINING THE FLORY-HUGGINS REACTION P A R A M E T E R FROM THE ACTIVATION ENERGIES OF THE VISCOUS FLOW OF POLYVINYLCHLORIDE SOLUTIONS* B. P. SHTARXMA~, T. L. YATSY~I~A and V. L. ]3ALAK~SKAYA (Received 29 July 1970) Tm~ F l o r y - H u g g i n s reaction parameter X is determined by various classical physical and chemical methods; osmometry, measurements of vapour pressure over solution, measurements of light scattering with solutions (using the second virial coefficient). I n addition to this, several indirect methods have been proposed: using the equilibrium swelling of a slightly crosslinked polymer [1], the intrinsic viscosity of the polymer in a given solvent and in 0 solvent [2], the reduction of melting point in a given solvent [3, 4].AU these methods are more or less complex from an experimental aspect. I t appears to us to be possible, however, in some cases to estimate Z by a simpler method. We have previously reported [5] the extremal dependence of the activation energy of viscous flow of polyvinylchloride (PVC) solutions in various plasticizers on the F l o r y Huggins reaction parameter and assumed t h a t one of the main causes of appearance of a m a x i m u m on curves AE-z m a y be the extremal dependence of the activation energy of viscous flow of the plasticizers themselves on parameter ZThe activation energies of viscous flow determined for plasticizers listed in an earlier paper [3] and also for dihexylphthalate were compared with activation energies of viscous flow of PVC solutions in plasticizers and with parameter X. * Vysokomol. soyed. A13: No. 7, 1683-1684, 1971.
(Received 20 January 1970) GEL permeation chromatography (GPC) is used to investigate molecular weight distribution (MWD) of polymers. The term "gel permeation chromatography" was introduced by Moor [1]. GPC is based on the varying abi]iity of molecules to permeate particles of a swollen polymeric crosslinked gel. Large molecules permeate gel particles to a lesser extent and
/1.
Fro. 1. Column used for gel permeation chromatography: / - - g l a s s tube containing the gel, 2--special tap, 3--vessel containing eluent, 4--siphon, 5 - - t e s t tube. during elution are the first to emerge from the column. Smaller molecules more readily permeate the gel particles and remain in the column for a longer time. Thus, molecules become distributed according to dimensions when passing the polymer solution through the column. Substances with molecular weights ranging from several hundreds to several millions can be analysed b y GPC. Various gels m a y be used. A comparison is made in the s t u d y [2] of the efficiency of separating molecules according to size on various porous materials. Crosslinked polystyrene gels [1-17] are most widely used. * Vysokomol. soyed. A18: No. 7, 1680--1683, 1971. 1893
1894
P.A.
Oxu:~v
et al.
~n
6O
20 I
30
/vO
50 V, nom.un.
60
Fig. 2. Elution curves of acetylcellulose fractions using a column 2 m in length. S o l v e n t - - T H F . Fractions with molecular weight 270,000 (1), 104,000 (2) 58,000 (3) and 11,000 (4). The effects of the concentration and a m o u n t of p o l y m e r introduced in the column, column temperature, rat~ of elution, length of column, various solvents on the accuracy of determining 1KWD of the polymer were examined in former papers [4, 5, 9, 10]. M W I ) determined b y GPC coincides satisfactorily with M W I ) determined b y other methods [7, 8]. The columns are normally calibrated with polymers of narrow M W D [1, 5, 16].
cl
./if?
80
2
60 ~0 2O
35
05
55
65
OO
50
60
70
V,/7om.un.
1~I~. 3. Elution curves of acetylcellulose fractions using a column 2 (a) a n d 3 m (b) in length. Solvent--acetone.
~ogn
5 " 5 ~ 5"0
3
0"0 I
O0
1
50
V, nom.un.
6g
/~zG. 4. Calibration curves for columns o f different lengths: 1 - - 2 m, s o l v e n t - - T H F ;
2 - - 2 m, acetone; 3 - - 3 m, acetone.
1895
Use of gel permeation chromatography
Studies of the theoretical and experimental problems o f GPC are reviewed in a separate paper [12]. A report is made [13, 17] of the use of GPC for the study of MWD of cellulose and its nitroesters. The authors of these studies point to the advantages of this m e t h o d of investigation over methods of fractional precipitation and solution [18-20]. An
2O
3O
O0
50
60
V ~ nom. un.
FIo. 5. Elution curves of unfractionated acetylcellulose samples using a column 2 m in length. S o lv e n t- - a c e to n e . SCA with a specific viscosity of 0.29 (1), 0.53 (2, 2'); first analysis (2), repeated analysis (2'). First, the method enables the polymer sample to be analysed in a few hours, while the methods mentioned previously require several days. Second, by selecting a column, the curve of lVIWD of the polymer can be increased in resolving power in the range of molecular weights in question. Third, GPC enables us to obtain not only weight-average an d number-average molecular weights and MWD, b u t also information concerning the degree of association in sohition. Fourth, differential curves of distribution are plotted directly from results of measurements in the apparatus. An a t t e m p t was made in this study to use GPC to determine the MW D of secondary cellulose acetates.
EXPERIMENTAL Chromatographic cohmms were filled with a erosslinked polystyrene gel of requisite porosity. Gels were obtained b y copolymerization of styrene and divinylbenzene. The column (Fig. 1) is a glass tube of about 10 m m in diameter and 2 or 3 m in length, which is uniformly filled with gel. 10 mg polymer in 1~/o solution was added to the upper part of the column. The polymer was then elated from the column with a solvent at a rate of 0.4 ml/lrdn. To plot the elation curve of the polymer, samples of 2.4 ml each were taken using a pipette-siphon. Polymer concentrations were determined in each of these samples using an ITR-1 interferometer. F r o m the result an ehition curve was plotted in coordinates V-An, where V is the eluent volume in nominal units (one nominal unit is 2.4 ml), An is the variation of the refractive index of the eluent in units of the scale of the I TR- 1 device. The column was calibrated with secondary cellulose acetate (SCA) fractions with molecular weights 270,000, 104,000, 58,000 and 11,000 obtained by fractional precipitation. T e t r a hydrofuran (TI-IF) and acetone were used as eluents and solvents for SCA.
RESU LTS T H F was used as solvent for SCA and eluent. Figure 2 shows that the thition volume~ v a r y for SCA fractions. F o r polymers with molecular weights of 270,000, 104,000, 58,00(~ and 11,000 the elation volumes were 35-5; 37.6; 40.2; 48.7 nora. units, respectively. These volumes were determined from the peak of the elation curve. T H F is the most 'extensively used solvent in GPC. This solvent, however, is not ideal. First, it is very subject to oxidation and consequently, to variation of refractive index.
1896
P. At. O ~ : ~ . v
et al.
T h i s n o r m a l l y causes a c h a n g e , or d i s p l a c e m e n t in t h e zero line o f t h e c u r v e , w h i c h is u n d e s i r able. A c e t o n e is a m o r e s t a b l e s o l v e n t f r o m t h i s a s p e c t a n d dissolves m a n y p o l y m e r s , i n c l u d i n g also SCA. I n a d d i t i o n , for a c e t o n e t h e r e f r a c t i v e i n d e x is lower t h a n for T H F , w h i c h increases t h e s e n s i t i v i t y of GPC. T h i s is v e r y i m p o r t a n t if t h e I T R - 1 d e v i c e is u s e d t o d e t e r m i n e t h e difference in r e f r a c t i v e indices. I n o r d e r t o use a c e t o n e , we t e s t e d gels, w h i c h were i n t e n d e d for o b t a i n i n g c l u t i o n c u r v e s b y G P C in TI-IF. I t a p p e a r e d t h a t gels w h i c h p r o v e d s a t i s f a c t o r y in f r a c t i o n a t i o n o f SCAt in T H F axe u n s a t i s f a c t o r y for use in a c e t o n e , since in a c e t o n e gel swells Jess s a t i s f a c t o r i l y t h a n in T H F . Therefore, t o use a c e t o n e in G P C of s e c o n d a r y a c e t a t e s , similar gels s u b j e c t e d t o special t r e a t m e n t were t a k e n . E x p e r i m e n t s s h o w (Fig. 3a) t h a t o n u s i n g a c e t o n e t h e s a m e efficiency c a n be o b t a i n e d in t h e s e p a r a t i o n o f m a c r o m o l e c u l e s as w h e n u s i n g T H F . F i g u r e 3a i n d i c a t e s t h a t for SCAt s a m p l e s f r a c t i o n a t e d in T H F (Fig. 2) r e s p e c t i v e e l u t i o n v o l u m e s o f a c e t o n e were 37.0; 39.1; 41.1; a n d 52.0 h e m . un. (curves 1-4, r e s p e c t i v e l y ) . F i g u r e 3b s h o w s e l u t i o n c u r v e s w i t h a c e t o n e o f SCAt f r a c t i o n s in a c o l u m n 3 m in l e n g t h a n d 8.5 m m in d i a m e t e r . T h e s e p a r a t i o n o f m o l e c u l e s a c c o r d i n g to d i m e n s i o n is m o r e satisf a c t o r y in t h i s case t h a n in 2 - m e t r e c o l u m n s . E l u t i o n v o l u m e s for SCAt f r a c t i o n s u s e d b y t h e a u t h o r s were 38.3; 42.6; 47.3; 57.6 nora. un. (curves 1-4, r e s p e c t i v e l y ) in o r d e r of decreasing m o l e c u l a r weights. Comparing results obtained using three- and two-meter columns it may be concluded t h a t t h e r e s o l v i n g p o w e r of t h e c o l u m n increases w i t h a n i n c r e a s e i n l e n g t h . H o w e v e r , t h e d u r a t i o n o f a n a l y s i s also increases p r o p o r t i o n a t e l y . F r a c t i o n a t i o n t i m e i n a 2 - m e t r e c o l u m n was a b o u t 5 hr, in a 3 - m e t r e c o l u m n , 8 hr. F r o m e l u t i o n v o l u m e s for e a c h o f t h e c o l u m n s c a l i b r a t i o n c u r v e s were p l o t t e d (Fig. 4) in c o o r d i n a t e s V - l o g d~l, w h e r e M is m o l e c u l a r weight, V is e l u t i o n v o l u m e . As s h o w n b y t h e s e c u r v e s a 3 - m e t r e c o l u m n is m o r e effective since t h e g r a d i e n t o f t h e c a l i b r a t i o n c u r v e is smaller. T h e c u r v e is a l m o s t a s t r a i g h t line, w h i c h is m o r e c o n v e n i e n t for c a l c u l a t i o n . F i g u r e 5 s h o w s e l u t i o n c u r v e s of u n f r a c t i o n a t e d SCAt aamples p r e p a r e d f r o m c o t t o n cellulose w i t h a specific v i s c o s i t y of a 0"25~oo s o l u t i o n in a c e t o n e of 0-53 a n d w o o d cellulose w i t h a specific v i s c o s i t y o f t h e s a m e s o l u t i o n o f 0-29. As s h o w n b y t h e Figure, u n f r a c t i o n a t e d s a m p l e s are d i s t r i b u t e d o v e r t h e whole r a n g e o f c a l i b r a t i o n . F i g u r e 5 also s h o w s r e s u l t s of r e p e a t e d e l u t i o n o f a s a m p l e w i t h a specific v i s c o s i t y o f 0-53 in t h e s a m e c o l u m n . T h e F i g u r e shows s a t i s f a c t o r y a g r e e m e n t b e t w e e n b o t h results. I t is t h u s s h o w n t h a t M W D of s e c o n d a r y cellulose a c e t a t e s c a n f a i r l y q u i c k l y a n d a c c u r a t e l y be d e t e r m i n e d b y GPC. I n c o n t r a s t t o classical m e t h o d s o f f r a c t i o n a t i o n (by f r a c t i o n a l s o l u t i o n a n d p r e c i p i t a t i o n ) , t h i s m e t h o d e n a b l e s us to d e t e r m i n e t h e a c t u a l M W D o f cellulose a c e t a t e s , since s e p a r a t i o n b y t h i s m e t h o d o n l y t a k e s place a c c o r d i n g t o m o l e c u l a r d i m e n s i o n a n d n o t a c c o r d i n g to t h e difference in solubility, w h e r e c h e m i c a l h e t e r o g e n e i t y of p o l y m e r c h a i n s h a s a n effect.
CONCLUSIONS At r a p i d m e t h o d was d e v e l o p e d for d e t e r m i n i n g t h e m o l e c u l a r w e i g h t d i s t r i b u t i o n o f s e c o n d a r y cellulose a c e t a t e s b y gel p e r m e a t i o n c h r o m a t o g r a p h y .
Translated by E. SEM~RE
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DETERMINING THE FLORY-HUGGINS REACTION P A R A M E T E R FROM THE ACTIVATION ENERGIES OF THE VISCOUS FLOW OF POLYVINYLCHLORIDE SOLUTIONS* B. P. SHTARXMA~, T. L. YATSY~I~A and V. L. ]3ALAK~SKAYA (Received 29 July 1970) Tm~ F l o r y - H u g g i n s reaction parameter X is determined by various classical physical and chemical methods; osmometry, measurements of vapour pressure over solution, measurements of light scattering with solutions (using the second virial coefficient). I n addition to this, several indirect methods have been proposed: using the equilibrium swelling of a slightly crosslinked polymer [1], the intrinsic viscosity of the polymer in a given solvent and in 0 solvent [2], the reduction of melting point in a given solvent [3, 4].AU these methods are more or less complex from an experimental aspect. I t appears to us to be possible, however, in some cases to estimate Z by a simpler method. We have previously reported [5] the extremal dependence of the activation energy of viscous flow of polyvinylchloride (PVC) solutions in various plasticizers on the F l o r y Huggins reaction parameter and assumed t h a t one of the main causes of appearance of a m a x i m u m on curves AE-z m a y be the extremal dependence of the activation energy of viscous flow of the plasticizers themselves on parameter ZThe activation energies of viscous flow determined for plasticizers listed in an earlier paper [3] and also for dihexylphthalate were compared with activation energies of viscous flow of PVC solutions in plasticizers and with parameter X. * Vysokomol. soyed. A13: No. 7, 1683-1684, 1971.