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Hydrodynamic and optical characteristics of cellulose macromolecules in cadoxene
Hydrodynamic and optical characteristics of cellulcee macromolecules
27~
19. G. S. HAMMOND, C. 8. WU, O. D. TRAPP, J. W ~ n W ~ [ l q and R. T. KEYS, J. A m e ~ Chem. Soc. 8S: 5394, 1960 20. Kh. S. BAGDASARYAN, Teoriya radikal'noi polimerizatsii (Theory of Radical Polymerization). Izd. "Nauka", 1966 21. Yc. T. DENISOV, Konstanty skorosti gomoliticheskikh zhidkofaznykh reaktsii (Rate~ Constants of Homolytic, Liquid-Phase Reactions). Izd. "Nauka" 1971 22. F. TUDOSH, Rassmotrenic kinetiki radikal'noi polimerizatsii na osnove gipotezy goryachikh radikalov (Discussion of the Kinetics of Radical Polymerization on the Basis. of the Hot-Radical Hypothesis). Izd. "Mir", 1966 (Russian translation, from Hungarian} 23. I. L. FABELINSKII; Uspekhi fiz. nauk 63: 355, 1957; ib/d. 77: 649, 1962 24. V. M. ZHULIN and M. G. GONIKTtERG, Tzv. Akad. Nauk SSSR, ser. khim., 331, 197~ 25. O. N. KARPIYKHIN, T. V. POKHOLOK and V. Ya. SHLYAPINTOKH; Vysokomol. soyed. A13: 22, 1971 (Translated in Polymer Sci. U.S.S.R. 13: 1, 23, 1971) 26. A. A. TATARENKO and V. S. PUDOV, Vysokomol. soyed. B9: 287, 1967 (Not translated in Polymer Sci. U.S.S.R.) 27. E. F. RUST, J. Amer. Chem. Soc. 79: 4000, 1957 28. D. SIMUNKOVA, R. RADO and O. iWLEJNEK, Kinetics and Mechanism of Polyreactions, Preprints, Budapest 4: 293, 1969 29. G.L. SLONIMSKH, A. A. ASKADS~[I and A. I. KITAIGORODSKH~ Vysokomol. soyed~ A12: 494, 1970 (Translated in Polymer Sci. U.S.S.R. 12: 3, 556, 1970)
HYDRODYNAMIC AND OPTICAL CHARACTERISTICS OF CELLULOSE MACROMOLECULES IN CADOXENE* S. HA. LYUB1-JgA,S. I. KLrl¢I~¢, I. A. STRELr~A, A. V. TROITSKAYA, A. K. KHR~U~OV a n d E. U. U~I~OV Institute of Macromolecular Compounds, U.S.S.R. Academy of Sciences
(Received 5 April 1976) The sedimentation 2, translational diffusion D, intrinsic viscosity [t/] and flow birefringence of solutions of cellulose linters in cadoxene have been studied over the range of molecular weights M = 2 X 103-7 X 105. The relationships obtained are [~]~ -~4.5x 104 M °'~, D----7.2x 10-6 M -°'Se and S-----1.8X10-16M°''2. The length of the ]~uhn segment in a 1 : 1 mixture of cadoxene and water is A-----100/~, which indicates the high rigidity of the cellulose molecule. In cadoxene cellulose has positive anisotropy, (al---as)----180X 10-35 cm a, due mainly to the contribution of anisotropy of molecular shape. Replacement of cadoxene by a cadoxene-water mixture (1 : 1.9) brings about an increase in [q] and (~i--~) as a result of increase in the rigidity of the polymer molecule. It is shown that the optical anisotropy of the cellulose molecule is the same, regardless of the nature of the cellulose (bacterial, cellulose hydrate, mercerized or linters). SOLUTIONS o f cellulose in eadoxene h a v e been studied c o m p a r a t i v e l y little [3, 4],. in c o n t r a s t t o cellulose esters in organic solvents. M a n y p r o b l e m s c o n n e c t e d with, * Vysokomol. soyed. A19: No. 2, 244-249, 1977.
S. YA. LY~smA e$ a/.
"280
t h e s t r u c t u r ~ o f t h e cellulose molecule (for e x a m p l e its r i g i d i t y a n d c o n f o r m a t i o n a n d t h e n a t u r e of its i n t e r a c t i o n w i t h t h e solvent) are still m a t t e r s for discussion. O p t i c a l a n i s o t r o p y , which is v e r y sensitive t o t h e c o n f o r m a t i o n of m a c r o m o l e eules, has n o t b e e n studied a t all for cellulose. T h e p r e s e n t p a p e r describes a c o m b i n e d i n v e s t i g a t i o n o f t h e optical (flow bire~fringence) a n d h y d r o d y n a m i c (viscosity, s e d i m e n t a t i o n , t r a n s l a t i o n a l diffusion) p r o p e r t i e s o f cellulose molecules o v e r a wide r a n g e o f m o l e c u l a r weights. (M), for d e t e r m i n a t i o n o f t h e c o n f o r m a t i o n a n d rigidity o f t h e cellulose chains a n d t o
where x~ is the coordinate of the sedimentation boundary maximum ~ the dispersion ~ f the sedimentation constants, co the angular velocity of rotation of the solution, D o the ,coefficient of diffusion and to the true sedimentation time. The dispersion of the sedimentation boundary ~a was calculated from the half,width of the sedimentation diagram ~=
1 -
-
2~/21n 2 Table 1 gives the values of ~quation [11, 12]
•
(S)
M:]M~, which are rela~ed to ~ by the well-known Schulz
MwM"- - 1 = ~am _~, l--b ~ ]
(31
where ~ is the dispersion with respect to molecular weight and (l--b) is the power index in the equation So = k ~ I-~. The solvents used were cadoxene (K~) containing 4-65~o of cadmium and 25.8% of ethylene diamine (the density of Kx was 1.061 g]cm s and its viscosity ~0~3.8 × 10-s P) and mixtures of cadoxenc and water in the ratio 1 : 1 (Ks) and 1 : 1.9 (K3). The constancy of the composition of the cadoxene was monitored carefully, because a small change in composition affects [~], S and D.
The hydrodynamic l~roper$ies of the ~acromolecules. T h e d e p e n d e n c e o f S, D ~ n d [~] on M , o v e r t h e r a n g e M ~ 2 × 103-7 × 105, for cellulose in K~ (Figs. 1 a n d 2)
Hydrodynamic and optical characteristics of cellulose macromolecules
~1
can be described by the following equations [r/]=4"5 X I 0 -~ M °'74,
(4)
D = 7 - 2 × 10 -5 M -°'Ss,
(5)
S=I'Sx
10 -15 .Z~°'4'~
(6)
I n Fig. 1 t h e s t r a i g h t line representing log [7] as a f u n c t i o n o f log M is d r a w n t h r o u g h points corresponding to fractions o f n a r r o w molecular weight distribuJ
TABLE 1. HYDRODYNAMICAND OPTICALCI~'AR&CTERISTICSOF CELLULOSEIN" CADOXENEK 1 ~ D Ka K|
Sample
LF L LI La L. L, L, L. L, Ls L. LIe Ln Lxl Lla L~, L1s Lie H B Lm
D OX l0 s I ~'8 X 101s 3.2 4.0 4.7 4.6 6-0 5-6 6-3
5-6 5.0 4.4 3.3 3.4 42.9 2-4
6.3 8.0 0"4, 9.2 0.9 1-1 5.6 7.0 1.0 1.0 0
2-0 2.2 1.6 1.7 1.6 1.5 1.1 1.2 0.8 0-5
3.5
4.5
2.3
MsDX M,IM~ X
10-8
70O 50O 380 290 230 205 151 146 102 85 72 63 57 38 26 24 7.5 2 100" 115" 520
1-1 1.1 1"6 1"5 1"5 1"5 2"0 1.4 1-5 2"6 2"0 3"0 2"0 1"5 1"9 5"0 6.0 1-5
r,4 x r-] [,1]x r~] x Xdl/gl0-S, [q] X 101° Xdl/gl0-', [q]
l O `°
10.0 7.8 5.9 4"7 4.5 5"0 4"1 3.7 2.8 3-2
26.2 22.8 23.5
8.5 7.2 5.8
23.6
3.6 4.7 3.6
18-0 18.0
2.5
18'0
2.1
23.0 23.2
1.9
22-0
0.9
18.8 18"6 18.7 15.0
19.5 18.2 -24.0 23-4 24.3
0.6
16.0
0.2 2.2 2.3 7.0
13"5 18-4 19.0 18"1
2-0 1-8 0.9
24.2 23.4
1-6
, ,
19-0
18"0
I
1.0 0-6
0.25 0.15 2.4 2.6 7.6
* M ealculat3dfrom[-'t]. t i o n (Mz/M w ~ 1.5). I t is seen f r o m Fig. 1 h o w e v e r t h a t p o l y d i s p e r s i t y does n o t s u b s t a n t i a l l y alter t h e course o f t h e e x p e r i m e n t a l [t/]-M relationship. T h e h i g h value o f ~ in t h e e q u a t i o n [tl]~KM~ indicates t h a t t h e cellulose m o ]ecules are in t h e f o r m o f p a r t i a l l y free d r a i n i n g coils. V o l u m e effects can be neglected, because t h e swelling coefficient o f cellulose in cado~ene is small (1.04-1.15) [4], even a t v e r y h i g h values o f M.
S. Y~ Lxu=aZ~ae=aZ.
~ 8 ~.
The theory of translational friction of worm-like chains [13, 14] wasused for quantitative determination of the equilibrium rigidity of cellulose molecules. For worm-like chains of length L greater than 2.2 A, Do is related to the length of the
0"0 o
. s!5
~ , ! o / f " °~'~
-0-8 ~
. 5~=
s-~~/o9 M
,
FIO.1. Dependence of log ~ on log [F/]for cellulose in caxioxene K=. Here and in Figs. 2 and 3 the circles of smaller diameter correspond to fractions with Ms/~fw< <1-5. K u h n statistical segment A, the diameter of the polymer chain d and molecular weight ~ , by the equation
k--~-= P
+
~-
1.~s ,
(7)
where ;Lis the projection of the monomer unit on the mo]ee~ar chain axis, which for cellulose is 5.15 4, and P is a hydrodynamic constant [13, 14]. By plotting t h e
.
a.,3
0.0
0.5
5.0
$5 /o9/4
Fio. 2. Dependence of log D (l) and log S (2) on log M, for cellulose in K=. experimental data corr~ponding to the lefthand side of equation (7) as a functio• of M ~ and taking P~-5,2, the value AD==97:E5 Awas obtained from the slope o f curve 1, Fig. 3,/~nd the intercept on the ordinate corresponds to d ~ 7 Jk.
Hydrodynamic and optioal characteristios of cellulose macromoleoules
288
The curve of the relationship M][y]~-f(M÷)shown in Fig. 3 (curve 2} was constructed from the viscometric measurements. This linear M/[~] curve correspondJ to the equation
<.1
,__,rlss,, 7 ,
A
where ~o~2.2 × 10is. The slope of culTe 2, Fig. 3 gives A,--~91-t- 7, which shows that AD and A, are in fairly good agreement. The length A-----94/t~ corresponds to a number of glucose units in the K uhn. segment [S]-~A/2~ 18, which is less by a factor of 2-5-2 than the corresponding number for cellulose derivatives (cellulose nitrate in acetone for example, where [$7=60 [17). Opticalproperliee. The length of the K u h n segment A, or the persistent length a=A/2, being a measure of the equilibrium rigidity of a chain macromolecule, also reflects another important property, namely orientational order in the molecule. [oM/~,Io I~
m~lr~.s],m*
,i~
2 ° ~ ° I
!
I
~ O
I
3
I
I .
5
I
I
7 Mtlz,fo "z
Fzct. 3. Dependence of M/[l#] (1) and D M I R T (2) on . l ~ for eelluloLqein Ki.
A more direct and much more sensitive measure of orientational ordering of molecular structure is optical anisotropy, which can be found from the birefringence (An) of polymer solutions [12]. Measurement of An of solutions of cellulose in cadoxene showed that all the samples give true molecular solutions, that An is positive in sign and is proportional to the shear stress g(~--~0)(~ is the viscosity of the solution) in all regions of rate gradient (g) studied. For all the samples thCquantity [An]g(~/--~o)]~0 is independent of polymer concentration. The values of [n]/[~]=lim [zin[g(~--~o)] are given g-*0
in Table 1, from which it is seen that [n]/[~] is practically constant over the range of M = 7 × 10s-3× 10I. The constancy of In]Jill while M changes by a factor of twenty five, indicates that the conformation of the cellulose coil (Gaussian coit)
284
S. YA. L Y U B I N A ¢~ cal.
remains unchanged. This is also shown by the fact t h a t in this range of M the dependence of log [t/] on log M (Fig. 1) is represented b y a single straight line, in contrast to evidence in the literature [15]. When M is reduced from 3 × 104 to 2 × 108 [n]/[~/] falls by 2 5 - 3 0 ~ , indicating some deviation of the conformation of the cellulose molecule from t h a t of a Gaussian random coil. The asymptotic limit ([n]/[~/])M~~ corresponds to the molecular weight region in which the cellulose molecules can be represented as Gaussian coils t h a t satisfy the K u h n formula [12] [n]
4z~ (nS+2) ~
[~] ----45kT
n
where n is the refractive index of the solvent and (~1--~) is the difference between the polarizabilities of the segment. For cellulose in cadoxene [n]/[y]=18-5 x 10 -l° a n d (1-2)=240 × 10~5 cm s. I n the system studied here the refractive-index increm e n t is fairlylarge (an/at=0.18) and the observed value of (~1--~) is the sum of the i n h e r e n t anisotropy (al--~), and the anisotropy of micro-shape (~l--a~)z, [12]. For cellulose the anisotropy of macro-shape is small and it can be neglected. The values of (al--a~)la found in reference [5] show t h a t the measured value of (al--a~) is for practical purpose equivalent %o the contribution of (~1--~,)I,. It is obvious t h a t the ~nisotropy of the glucose unit (all - - ~ . ) is small in absolute value, b u t it has not yet been possible to determine the sign of (aU --ax). Investigation of the flow birefringence of solutions of different types of cellulose (linters, mercerized, bacterial and cellulose hydrate), which differ in supermolecular structure in fibre film form (degree of crystallinity, type of crystal lattice) [16], showed t h a t in solution in cadoxene the optical anisotropy of the molecules i s t h e same in the different types of cellulose. T A B L E 2. V A L U E S OZ [~] A~ v [n]/[~]~OB CELLULOSE A N D H E 0 IN CADOXm~'S--WA~-~ ~IXT~.~ES /
Polymer
[~]I[.]x
[,] x 10-.. dl/g
K1
]
K,
I K°
l
HEC LF
3.2 8"5
L L, L,o
7.2 2"5 1.6
l
3.6 10.0 7.8 3.0 i 2.0
4"5 11.0 8.0 3"4 2.2
I H,O*
10 i.s. i.s. i.s. i.s.
K,
I K,
28 19 18 18 18
35 26 23 22 23
[
10'0
K, 42 30 28 33 29
I HIe* 58
i.e. i.s. i.s. i.s.
* l.s. denotes lusoluble.
The effect of the nature of the ~oZvent. The comparatively low value of A for cellulose is evidently explained by the specific type of interaction between cadoxene and the cellulose molecule. To obtain confirmation of this idea [~/] and [n]/[t/] of cellulose and hydroxyethylceUulose (HEC) were measured in eadoxene and in eadoxene-water mixture. I t is seen from Table 2 t h a t for cellulose, on passing
Hydrodynamic and optioal eharaet~ti¢~ of eelluloso maoromoloeules
2~
from K1 to Ks i n c r e a s e s b y 2~-30% and [n]/[~] increases b y 50%. I n t h e case o f H E C this replacement of cadoxene b y water brings about a threefold increase in [#], while the birefringence is doubled. The molecular weight of the samples does not change when the composition of the solvent is altered. The second virial coefficient ,42 for HEC is 12× 10 -4 in eadoxene and 4× 10 -4 in water, therefore the increase in [t/] on passing from cadoxene to water cannot be explained b y volume effects [17]. W i t h o u t considering the very complex and debatable question of the nature of the interaction of the cadmium-ethylenediamine complex with glucose units [18, 19], we would point out t h a t cadoxene disrupts intramoleeular hydrogen bonds in cellulose. I t m a y therefore be assumed t h a t on passing from a good to a poorer solvent (dilution of the cellulose or HEC solution with water)' intramolecular hydrogen bonds can form again, giving rise to intramoleeular "crosslinking", which increases the effective rigidity of the chain, which in turn results in increase in [~/] and [n]/[~7]. Thus in contrast to polymers with flexible chains, in the case of cellulose in cadoxene, as for cellulose esters and ethers in organic solvents [20-22], the thermodynamic flexibility of the chain is strongly dependent on the nature of the solvent. The authors are deeply grateful to V. N. Tsvetkov for his interest in and valuable discussion of the work. Tranelat~d by E. O. Pn~LLrPS REFERENCES
1. V. N. TSYETKOV, Uspekhi khimii 38: 1675, 1969 2. D. W. TANNER and G. G. BERRY, J. Polymer Sci., Polymer Phys. Ed. 12: 541, 1974 3. H. rINK, Arkiv ke~ai 14: 195, 1959; L. S. BOLOTNIKOVA and T. I. SAMSONOVA, Zh. prikl, khim. 84: 659, 1961 4. D. HENLEY, Arkiv kemi 18: 327, 1962 5. S. I. KLENIN, S. Ya. LYUBINA, A. V. TROITSKAYA, I. A. STRELINA, V. I. K U R LYANKINA and V. A. MOLOTKOV, Vysokomol. soyed. A17: 1975, 1975 (Translated
in Polymer Sei. U.S.S.R. 17: 9, 2275, 1975) 6. R. Z. WHISTLER (Ed.), Methods in Carbohydrate Chemistry, Vol. 3, p. 4, l~w York, 1963 7. A. K. K I ~ I P U N O V , Ye. A. PLISKO, L. A. LAIUS, Yu. G. BAKLAGINA, V. V. PETROVA and V. A. GERASIMOVA, Vysokomol. soyed. B17: 600, 1975 (Not translated in
Polymer Sci. U.S.S.R.) 8. S. WATANABE, J. HAYASHI and T. AKAHORI, J. Polymer Sci., Polymer Chem. Ed. 12: 1065, 1974 9. O. P. KOZ'MINA, V. L KURLYANKINA, S. ZHDAN-PUS~TNA and V. A. MOLOTKOV, Vysokomol. soyed. 5: 492, 1963 (Translated in Polymer Sci. U.S.S.R. 5: 4~ 1160, 1963) 10. S. Ye. BRESLER and S. Ya. FRENKEL', Zh. tekh. fiz. 23: 1502, 1953 11. G. SCHULZ and F. BLASC~E, J. prakt. Chem. 158: 130, 1941 12. V. N. TSVETKOV, V. Ye. ESKIN and S. Ya. FREN~EL', Struktura makromoleku| v rastvore (Structure of Macromolecules in Solution). Izd. "Nauka", 1964 13. H. KUHN, W. KUHN and A. SH.RERBERG, J. Polymer Sci. 14: 193, 1953 14. J. HEARST and W. STOCKMAYER, J. Chem. Phys. 37: 1425, 1962
~86
V. Yz. G~,' ~ ~ .
15. W. BROWN, Sb. Tselluloza i eye proizvodnye (Collected papers. Cellulose and its I)erI. vatives). Vol. 1, p. 450, Izd. "Mir", 1974 (Russian translation) 16. D. J. JONES, Sb. Tselluloza i eye proizvodnye (Collected papers Cellulose and its Derivatives). Vol. ], p. 119, Izd. "Mir", 1974 (Russian translation) 17. W. J. BROWN, T A P P I 49: 367, 1966 18. H. VINK and G. DAHTSTR~M, Makromolek. Chem. 109: 249, 1967 19. B. LINDBERG and B. SWAN, Acta Chem. Scand. 17: 913, 1963 20. P. J. FLORY, O. K. SPURR and D. K. CARPENTER, J. Polymer SoL 27: 231, 1958 21. L. MAND~.L~RR.N and P. J, FLORY, J. Amer. Chem. Soc. 74: 2517, 1952 22. V. N. TSVETKOV, S. Ya. LYUBINA, S. I. KLENIN, I. A. STRELINA, A. V. TROITSKAYA and V. L KURLYANKINA, Vysokomol. soyed. A15: 691, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 3, 781, 1973)
PHYSICOCI~MICAL CRITEP~A OF THE EXTRUDABILITY OF POLYMERS* V. Y~.. GUT.', G. V. VI~OGRAnOV,YU. G. YA_~OVSK~ and T. N. MUROMOVA Moscow Teohnologioal Institute of the Meat and Mil~ Industry (R~/vcd 8 Apt// 1976) Well defined physicochemical criteria are required 'for assessment of the extrudability of macromolecular compounds. A general scheme is proposed, which includes determination of the optlm~l rate of shear and shear stress, at temperatures that do not cause thermal decomposition of the polymeric systems, Systems based on polyiso. prene hydrocbloride (FHC) are examined as examples for rheological and physioo. chemical analysis. The dependence of G' and G" on frequency (~) was investigated b y a dynamic method. For construction of curves of the dependence of effective visco. sity on rate of shear, and of flow curves of the compositions, use was made of the principle of correspondence of rheological relationships obtained for periodic, small amplitude deformation and for continuous deformation under conditions of steady flow, which enables a rational selection to be made of the make-up af polymeric compositions to ensure placement of the flow curves in the "extrudability zone". Further investigation of the compositions under dynamic test conditions similar to the conditions of processing of materials by extrusion, has enabled working conditions for production of PHC film to be selected. I N SOME instances linking of rheological a s p e c t s of t h e e x t r u s i o n process w i t h c h e m i c a l aspects gives rise t o t h e n e e d for a general principle, w h e r e b y it w o u l d b e possible t o d e t e r m i n e t h e conditions for ensuring e x t r u d a b i l i t y o f a composit i o n b a s e on a g i v e n p o l y m e r . T h e a i m of t h e p r e s e n t i n v e s t i g a t i o n w a s t o f i n d p h y s i c o c h e m i c a l criteria o f e x t r u d a b i l i t y o f p o l y m e r compositions. I n s o m e i n s t a n c e s use o f t h e e x t r u s i o n m e t h o d is r e s t r i c t e d b y t h e processing * Vysokomol. soyed. A19: No. 2, 250-256, 1977.
27~
19. G. S. HAMMOND, C. 8. WU, O. D. TRAPP, J. W ~ n W ~ [ l q and R. T. KEYS, J. A m e ~ Chem. Soc. 8S: 5394, 1960 20. Kh. S. BAGDASARYAN, Teoriya radikal'noi polimerizatsii (Theory of Radical Polymerization). Izd. "Nauka", 1966 21. Yc. T. DENISOV, Konstanty skorosti gomoliticheskikh zhidkofaznykh reaktsii (Rate~ Constants of Homolytic, Liquid-Phase Reactions). Izd. "Nauka" 1971 22. F. TUDOSH, Rassmotrenic kinetiki radikal'noi polimerizatsii na osnove gipotezy goryachikh radikalov (Discussion of the Kinetics of Radical Polymerization on the Basis. of the Hot-Radical Hypothesis). Izd. "Mir", 1966 (Russian translation, from Hungarian} 23. I. L. FABELINSKII; Uspekhi fiz. nauk 63: 355, 1957; ib/d. 77: 649, 1962 24. V. M. ZHULIN and M. G. GONIKTtERG, Tzv. Akad. Nauk SSSR, ser. khim., 331, 197~ 25. O. N. KARPIYKHIN, T. V. POKHOLOK and V. Ya. SHLYAPINTOKH; Vysokomol. soyed. A13: 22, 1971 (Translated in Polymer Sci. U.S.S.R. 13: 1, 23, 1971) 26. A. A. TATARENKO and V. S. PUDOV, Vysokomol. soyed. B9: 287, 1967 (Not translated in Polymer Sci. U.S.S.R.) 27. E. F. RUST, J. Amer. Chem. Soc. 79: 4000, 1957 28. D. SIMUNKOVA, R. RADO and O. iWLEJNEK, Kinetics and Mechanism of Polyreactions, Preprints, Budapest 4: 293, 1969 29. G.L. SLONIMSKH, A. A. ASKADS~[I and A. I. KITAIGORODSKH~ Vysokomol. soyed~ A12: 494, 1970 (Translated in Polymer Sci. U.S.S.R. 12: 3, 556, 1970)
HYDRODYNAMIC AND OPTICAL CHARACTERISTICS OF CELLULOSE MACROMOLECULES IN CADOXENE* S. HA. LYUB1-JgA,S. I. KLrl¢I~¢, I. A. STRELr~A, A. V. TROITSKAYA, A. K. KHR~U~OV a n d E. U. U~I~OV Institute of Macromolecular Compounds, U.S.S.R. Academy of Sciences
(Received 5 April 1976) The sedimentation 2, translational diffusion D, intrinsic viscosity [t/] and flow birefringence of solutions of cellulose linters in cadoxene have been studied over the range of molecular weights M = 2 X 103-7 X 105. The relationships obtained are [~]~ -~4.5x 104 M °'~, D----7.2x 10-6 M -°'Se and S-----1.8X10-16M°''2. The length of the ]~uhn segment in a 1 : 1 mixture of cadoxene and water is A-----100/~, which indicates the high rigidity of the cellulose molecule. In cadoxene cellulose has positive anisotropy, (al---as)----180X 10-35 cm a, due mainly to the contribution of anisotropy of molecular shape. Replacement of cadoxene by a cadoxene-water mixture (1 : 1.9) brings about an increase in [q] and (~i--~) as a result of increase in the rigidity of the polymer molecule. It is shown that the optical anisotropy of the cellulose molecule is the same, regardless of the nature of the cellulose (bacterial, cellulose hydrate, mercerized or linters). SOLUTIONS o f cellulose in eadoxene h a v e been studied c o m p a r a t i v e l y little [3, 4],. in c o n t r a s t t o cellulose esters in organic solvents. M a n y p r o b l e m s c o n n e c t e d with, * Vysokomol. soyed. A19: No. 2, 244-249, 1977.
S. YA. LY~smA e$ a/.
"280
t h e s t r u c t u r ~ o f t h e cellulose molecule (for e x a m p l e its r i g i d i t y a n d c o n f o r m a t i o n a n d t h e n a t u r e of its i n t e r a c t i o n w i t h t h e solvent) are still m a t t e r s for discussion. O p t i c a l a n i s o t r o p y , which is v e r y sensitive t o t h e c o n f o r m a t i o n of m a c r o m o l e eules, has n o t b e e n studied a t all for cellulose. T h e p r e s e n t p a p e r describes a c o m b i n e d i n v e s t i g a t i o n o f t h e optical (flow bire~fringence) a n d h y d r o d y n a m i c (viscosity, s e d i m e n t a t i o n , t r a n s l a t i o n a l diffusion) p r o p e r t i e s o f cellulose molecules o v e r a wide r a n g e o f m o l e c u l a r weights. (M), for d e t e r m i n a t i o n o f t h e c o n f o r m a t i o n a n d rigidity o f t h e cellulose chains a n d t o
where x~ is the coordinate of the sedimentation boundary maximum ~ the dispersion ~ f the sedimentation constants, co the angular velocity of rotation of the solution, D o the ,coefficient of diffusion and to the true sedimentation time. The dispersion of the sedimentation boundary ~a was calculated from the half,width of the sedimentation diagram ~=
1 -
-
2~/21n 2 Table 1 gives the values of ~quation [11, 12]
•
(S)
M:]M~, which are rela~ed to ~ by the well-known Schulz
MwM"- - 1 = ~am _~, l--b ~ ]
(31
where ~ is the dispersion with respect to molecular weight and (l--b) is the power index in the equation So = k ~ I-~. The solvents used were cadoxene (K~) containing 4-65~o of cadmium and 25.8% of ethylene diamine (the density of Kx was 1.061 g]cm s and its viscosity ~0~3.8 × 10-s P) and mixtures of cadoxenc and water in the ratio 1 : 1 (Ks) and 1 : 1.9 (K3). The constancy of the composition of the cadoxene was monitored carefully, because a small change in composition affects [~], S and D.
The hydrodynamic l~roper$ies of the ~acromolecules. T h e d e p e n d e n c e o f S, D ~ n d [~] on M , o v e r t h e r a n g e M ~ 2 × 103-7 × 105, for cellulose in K~ (Figs. 1 a n d 2)
Hydrodynamic and optical characteristics of cellulose macromolecules
~1
can be described by the following equations [r/]=4"5 X I 0 -~ M °'74,
(4)
D = 7 - 2 × 10 -5 M -°'Ss,
(5)
S=I'Sx
10 -15 .Z~°'4'~
(6)
I n Fig. 1 t h e s t r a i g h t line representing log [7] as a f u n c t i o n o f log M is d r a w n t h r o u g h points corresponding to fractions o f n a r r o w molecular weight distribuJ
TABLE 1. HYDRODYNAMICAND OPTICALCI~'AR&CTERISTICSOF CELLULOSEIN" CADOXENEK 1 ~ D Ka K|
Sample
LF L LI La L. L, L, L. L, Ls L. LIe Ln Lxl Lla L~, L1s Lie H B Lm
D OX l0 s I ~'8 X 101s 3.2 4.0 4.7 4.6 6-0 5-6 6-3
5-6 5.0 4.4 3.3 3.4 42.9 2-4
6.3 8.0 0"4, 9.2 0.9 1-1 5.6 7.0 1.0 1.0 0
2-0 2.2 1.6 1.7 1.6 1.5 1.1 1.2 0.8 0-5
3.5
4.5
2.3
MsDX M,IM~ X
10-8
70O 50O 380 290 230 205 151 146 102 85 72 63 57 38 26 24 7.5 2 100" 115" 520
1-1 1.1 1"6 1"5 1"5 1"5 2"0 1.4 1-5 2"6 2"0 3"0 2"0 1"5 1"9 5"0 6.0 1-5
r,4 x r-] [,1]x r~] x Xdl/gl0-S, [q] X 101° Xdl/gl0-', [q]
l O `°
10.0 7.8 5.9 4"7 4.5 5"0 4"1 3.7 2.8 3-2
26.2 22.8 23.5
8.5 7.2 5.8
23.6
3.6 4.7 3.6
18-0 18.0
2.5
18'0
2.1
23.0 23.2
1.9
22-0
0.9
18.8 18"6 18.7 15.0
19.5 18.2 -24.0 23-4 24.3
0.6
16.0
0.2 2.2 2.3 7.0
13"5 18-4 19.0 18"1
2-0 1-8 0.9
24.2 23.4
1-6
, ,
19-0
18"0
I
1.0 0-6
0.25 0.15 2.4 2.6 7.6
* M ealculat3dfrom[-'t]. t i o n (Mz/M w ~ 1.5). I t is seen f r o m Fig. 1 h o w e v e r t h a t p o l y d i s p e r s i t y does n o t s u b s t a n t i a l l y alter t h e course o f t h e e x p e r i m e n t a l [t/]-M relationship. T h e h i g h value o f ~ in t h e e q u a t i o n [tl]~KM~ indicates t h a t t h e cellulose m o ]ecules are in t h e f o r m o f p a r t i a l l y free d r a i n i n g coils. V o l u m e effects can be neglected, because t h e swelling coefficient o f cellulose in cado~ene is small (1.04-1.15) [4], even a t v e r y h i g h values o f M.
S. Y~ Lxu=aZ~ae=aZ.
~ 8 ~.
The theory of translational friction of worm-like chains [13, 14] wasused for quantitative determination of the equilibrium rigidity of cellulose molecules. For worm-like chains of length L greater than 2.2 A, Do is related to the length of the
0"0 o
. s!5
~ , ! o / f " °~'~
-0-8 ~
. 5~=
s-~~/o9 M
,
FIO.1. Dependence of log ~ on log [F/]for cellulose in caxioxene K=. Here and in Figs. 2 and 3 the circles of smaller diameter correspond to fractions with Ms/~fw< <1-5. K u h n statistical segment A, the diameter of the polymer chain d and molecular weight ~ , by the equation
k--~-= P
+
~-
1.~s ,
(7)
where ;Lis the projection of the monomer unit on the mo]ee~ar chain axis, which for cellulose is 5.15 4, and P is a hydrodynamic constant [13, 14]. By plotting t h e
.
a.,3
0.0
0.5
5.0
$5 /o9/4
Fio. 2. Dependence of log D (l) and log S (2) on log M, for cellulose in K=. experimental data corr~ponding to the lefthand side of equation (7) as a functio• of M ~ and taking P~-5,2, the value AD==97:E5 Awas obtained from the slope o f curve 1, Fig. 3,/~nd the intercept on the ordinate corresponds to d ~ 7 Jk.
Hydrodynamic and optioal characteristios of cellulose macromoleoules
288
The curve of the relationship M][y]~-f(M÷)shown in Fig. 3 (curve 2} was constructed from the viscometric measurements. This linear M/[~] curve correspondJ to the equation
<.1
,__,rlss,, 7 ,
A
where ~o~2.2 × 10is. The slope of culTe 2, Fig. 3 gives A,--~91-t- 7, which shows that AD and A, are in fairly good agreement. The length A-----94/t~ corresponds to a number of glucose units in the K uhn. segment [S]-~A/2~ 18, which is less by a factor of 2-5-2 than the corresponding number for cellulose derivatives (cellulose nitrate in acetone for example, where [$7=60 [17). Opticalproperliee. The length of the K u h n segment A, or the persistent length a=A/2, being a measure of the equilibrium rigidity of a chain macromolecule, also reflects another important property, namely orientational order in the molecule. [oM/~,Io I~
m~lr~.s],m*
,i~
2 ° ~ ° I
!
I
~ O
I
3
I
I .
5
I
I
7 Mtlz,fo "z
Fzct. 3. Dependence of M/[l#] (1) and D M I R T (2) on . l ~ for eelluloLqein Ki.
A more direct and much more sensitive measure of orientational ordering of molecular structure is optical anisotropy, which can be found from the birefringence (An) of polymer solutions [12]. Measurement of An of solutions of cellulose in cadoxene showed that all the samples give true molecular solutions, that An is positive in sign and is proportional to the shear stress g(~--~0)(~ is the viscosity of the solution) in all regions of rate gradient (g) studied. For all the samples thCquantity [An]g(~/--~o)]~0 is independent of polymer concentration. The values of [n]/[~]=lim [zin[g(~--~o)] are given g-*0
in Table 1, from which it is seen that [n]/[~] is practically constant over the range of M = 7 × 10s-3× 10I. The constancy of In]Jill while M changes by a factor of twenty five, indicates that the conformation of the cellulose coil (Gaussian coit)
284
S. YA. L Y U B I N A ¢~ cal.
remains unchanged. This is also shown by the fact t h a t in this range of M the dependence of log [t/] on log M (Fig. 1) is represented b y a single straight line, in contrast to evidence in the literature [15]. When M is reduced from 3 × 104 to 2 × 108 [n]/[~/] falls by 2 5 - 3 0 ~ , indicating some deviation of the conformation of the cellulose molecule from t h a t of a Gaussian random coil. The asymptotic limit ([n]/[~/])M~~ corresponds to the molecular weight region in which the cellulose molecules can be represented as Gaussian coils t h a t satisfy the K u h n formula [12] [n]
4z~ (nS+2) ~
[~] ----45kT
n
where n is the refractive index of the solvent and (~1--~) is the difference between the polarizabilities of the segment. For cellulose in cadoxene [n]/[y]=18-5 x 10 -l° a n d (1-2)=240 × 10~5 cm s. I n the system studied here the refractive-index increm e n t is fairlylarge (an/at=0.18) and the observed value of (~1--~) is the sum of the i n h e r e n t anisotropy (al--~), and the anisotropy of micro-shape (~l--a~)z, [12]. For cellulose the anisotropy of macro-shape is small and it can be neglected. The values of (al--a~)la found in reference [5] show t h a t the measured value of (al--a~) is for practical purpose equivalent %o the contribution of (~1--~,)I,. It is obvious t h a t the ~nisotropy of the glucose unit (all - - ~ . ) is small in absolute value, b u t it has not yet been possible to determine the sign of (aU --ax). Investigation of the flow birefringence of solutions of different types of cellulose (linters, mercerized, bacterial and cellulose hydrate), which differ in supermolecular structure in fibre film form (degree of crystallinity, type of crystal lattice) [16], showed t h a t in solution in cadoxene the optical anisotropy of the molecules i s t h e same in the different types of cellulose. T A B L E 2. V A L U E S OZ [~] A~ v [n]/[~]~OB CELLULOSE A N D H E 0 IN CADOXm~'S--WA~-~ ~IXT~.~ES /
Polymer
[~]I[.]x
[,] x 10-.. dl/g
K1
]
K,
I K°
l
HEC LF
3.2 8"5
L L, L,o
7.2 2"5 1.6
l
3.6 10.0 7.8 3.0 i 2.0
4"5 11.0 8.0 3"4 2.2
I H,O*
10 i.s. i.s. i.s. i.s.
K,
I K,
28 19 18 18 18
35 26 23 22 23
[
10'0
K, 42 30 28 33 29
I HIe* 58
i.e. i.s. i.s. i.s.
* l.s. denotes lusoluble.
The effect of the nature of the ~oZvent. The comparatively low value of A for cellulose is evidently explained by the specific type of interaction between cadoxene and the cellulose molecule. To obtain confirmation of this idea [~/] and [n]/[t/] of cellulose and hydroxyethylceUulose (HEC) were measured in eadoxene and in eadoxene-water mixture. I t is seen from Table 2 t h a t for cellulose, on passing
Hydrodynamic and optioal eharaet~ti¢~ of eelluloso maoromoloeules
2~
from K1 to Ks i n c r e a s e s b y 2~-30% and [n]/[~] increases b y 50%. I n t h e case o f H E C this replacement of cadoxene b y water brings about a threefold increase in [#], while the birefringence is doubled. The molecular weight of the samples does not change when the composition of the solvent is altered. The second virial coefficient ,42 for HEC is 12× 10 -4 in eadoxene and 4× 10 -4 in water, therefore the increase in [t/] on passing from cadoxene to water cannot be explained b y volume effects [17]. W i t h o u t considering the very complex and debatable question of the nature of the interaction of the cadmium-ethylenediamine complex with glucose units [18, 19], we would point out t h a t cadoxene disrupts intramoleeular hydrogen bonds in cellulose. I t m a y therefore be assumed t h a t on passing from a good to a poorer solvent (dilution of the cellulose or HEC solution with water)' intramolecular hydrogen bonds can form again, giving rise to intramoleeular "crosslinking", which increases the effective rigidity of the chain, which in turn results in increase in [~/] and [n]/[~7]. Thus in contrast to polymers with flexible chains, in the case of cellulose in cadoxene, as for cellulose esters and ethers in organic solvents [20-22], the thermodynamic flexibility of the chain is strongly dependent on the nature of the solvent. The authors are deeply grateful to V. N. Tsvetkov for his interest in and valuable discussion of the work. Tranelat~d by E. O. Pn~LLrPS REFERENCES
1. V. N. TSYETKOV, Uspekhi khimii 38: 1675, 1969 2. D. W. TANNER and G. G. BERRY, J. Polymer Sci., Polymer Phys. Ed. 12: 541, 1974 3. H. rINK, Arkiv ke~ai 14: 195, 1959; L. S. BOLOTNIKOVA and T. I. SAMSONOVA, Zh. prikl, khim. 84: 659, 1961 4. D. HENLEY, Arkiv kemi 18: 327, 1962 5. S. I. KLENIN, S. Ya. LYUBINA, A. V. TROITSKAYA, I. A. STRELINA, V. I. K U R LYANKINA and V. A. MOLOTKOV, Vysokomol. soyed. A17: 1975, 1975 (Translated
in Polymer Sei. U.S.S.R. 17: 9, 2275, 1975) 6. R. Z. WHISTLER (Ed.), Methods in Carbohydrate Chemistry, Vol. 3, p. 4, l~w York, 1963 7. A. K. K I ~ I P U N O V , Ye. A. PLISKO, L. A. LAIUS, Yu. G. BAKLAGINA, V. V. PETROVA and V. A. GERASIMOVA, Vysokomol. soyed. B17: 600, 1975 (Not translated in
Polymer Sci. U.S.S.R.) 8. S. WATANABE, J. HAYASHI and T. AKAHORI, J. Polymer Sci., Polymer Chem. Ed. 12: 1065, 1974 9. O. P. KOZ'MINA, V. L KURLYANKINA, S. ZHDAN-PUS~TNA and V. A. MOLOTKOV, Vysokomol. soyed. 5: 492, 1963 (Translated in Polymer Sci. U.S.S.R. 5: 4~ 1160, 1963) 10. S. Ye. BRESLER and S. Ya. FRENKEL', Zh. tekh. fiz. 23: 1502, 1953 11. G. SCHULZ and F. BLASC~E, J. prakt. Chem. 158: 130, 1941 12. V. N. TSVETKOV, V. Ye. ESKIN and S. Ya. FREN~EL', Struktura makromoleku| v rastvore (Structure of Macromolecules in Solution). Izd. "Nauka", 1964 13. H. KUHN, W. KUHN and A. SH.RERBERG, J. Polymer Sci. 14: 193, 1953 14. J. HEARST and W. STOCKMAYER, J. Chem. Phys. 37: 1425, 1962
~86
V. Yz. G~,' ~ ~ .
15. W. BROWN, Sb. Tselluloza i eye proizvodnye (Collected papers. Cellulose and its I)erI. vatives). Vol. 1, p. 450, Izd. "Mir", 1974 (Russian translation) 16. D. J. JONES, Sb. Tselluloza i eye proizvodnye (Collected papers Cellulose and its Derivatives). Vol. ], p. 119, Izd. "Mir", 1974 (Russian translation) 17. W. J. BROWN, T A P P I 49: 367, 1966 18. H. VINK and G. DAHTSTR~M, Makromolek. Chem. 109: 249, 1967 19. B. LINDBERG and B. SWAN, Acta Chem. Scand. 17: 913, 1963 20. P. J. FLORY, O. K. SPURR and D. K. CARPENTER, J. Polymer SoL 27: 231, 1958 21. L. MAND~.L~RR.N and P. J, FLORY, J. Amer. Chem. Soc. 74: 2517, 1952 22. V. N. TSVETKOV, S. Ya. LYUBINA, S. I. KLENIN, I. A. STRELINA, A. V. TROITSKAYA and V. L KURLYANKINA, Vysokomol. soyed. A15: 691, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 3, 781, 1973)
PHYSICOCI~MICAL CRITEP~A OF THE EXTRUDABILITY OF POLYMERS* V. Y~.. GUT.', G. V. VI~OGRAnOV,YU. G. YA_~OVSK~ and T. N. MUROMOVA Moscow Teohnologioal Institute of the Meat and Mil~ Industry (R~/vcd 8 Apt// 1976) Well defined physicochemical criteria are required 'for assessment of the extrudability of macromolecular compounds. A general scheme is proposed, which includes determination of the optlm~l rate of shear and shear stress, at temperatures that do not cause thermal decomposition of the polymeric systems, Systems based on polyiso. prene hydrocbloride (FHC) are examined as examples for rheological and physioo. chemical analysis. The dependence of G' and G" on frequency (~) was investigated b y a dynamic method. For construction of curves of the dependence of effective visco. sity on rate of shear, and of flow curves of the compositions, use was made of the principle of correspondence of rheological relationships obtained for periodic, small amplitude deformation and for continuous deformation under conditions of steady flow, which enables a rational selection to be made of the make-up af polymeric compositions to ensure placement of the flow curves in the "extrudability zone". Further investigation of the compositions under dynamic test conditions similar to the conditions of processing of materials by extrusion, has enabled working conditions for production of PHC film to be selected. I N SOME instances linking of rheological a s p e c t s of t h e e x t r u s i o n process w i t h c h e m i c a l aspects gives rise t o t h e n e e d for a general principle, w h e r e b y it w o u l d b e possible t o d e t e r m i n e t h e conditions for ensuring e x t r u d a b i l i t y o f a composit i o n b a s e on a g i v e n p o l y m e r . T h e a i m of t h e p r e s e n t i n v e s t i g a t i o n w a s t o f i n d p h y s i c o c h e m i c a l criteria o f e x t r u d a b i l i t y o f p o l y m e r compositions. I n s o m e i n s t a n c e s use o f t h e e x t r u s i o n m e t h o d is r e s t r i c t e d b y t h e processing * Vysokomol. soyed. A19: No. 2, 250-256, 1977.