Study of the supermolecular organization in films of cellulose derivatives

Supermolecular organization in films of cellulose derivatives

1715

REFERENCES 1. A. A. BERLIN, V. A. GRIGOROVSKAYA and G. V. BELOVA, Vysokomol. soyed. A12: 2351, 1970 (Translated in P o l y m e r Sei. U.S.S.R. 12: 10, 2667, 1970) 2. A. V. CHERNOBAI, Zh. S. TIRAK'YANTS and R. Ira. DELYAT1TSKAYA, Pribory i tekh. eksper., No. 6, 58, 1967 3. I. PAROL and K. OKOH, Roczn. chem. 44: 2099, 1970 4. A. REMBAUM and A. EISENBERG, Macromol. Rev. 4: 57, 1966 5. G. I. LASHKOV, M. G. KRAKOVYAK, N. S. SHELEKHOV and S. S. SKOROKHODOV, ]Dok]. Akad. N a u k S S S R 214: 850, 1974 6. Ye. V. ANUFRIEVA, Yu. Ya. GOTT.IR, M. G. KRAKOVYAK a n d S. S. SKOROKHODOV, Vysokomol. soyed. A14: 1430, 1972 (Translated in Polymer Sei. U.S.S.R. 14: 6, 1604, 1972) 7. M. G. KRAKOVYAK, Ye. V. ANUFRIEVA, T. D. ANAN'EVA, V. B. LUSHCHUg~ N. S. SHELEKHOV and S. S. SKOROKHODOV, Vysokomol. soyed. A I 7 : 1983, 1975 (Translated in Polymer Sci. U.S.S.R. 14: 9, 2284, 1975) 8. E. FETTES (Ed.), Khimicheskie real~tsii polimerov (The Chemical Reactions of Polymers). Izd. "Mir", 246, 1967 9. G. A. OLAH, Accounts Chem. Res. 4: 240, 1971 10. R. O. SYMCOX and J. D. COTMAN, J. Polymer Sei. 5, A - l : 417, 1967 11. R. LEUTE and S. WINSTEIN, Tetrahedron Letters 26: 2475, 1967 12. G. MONTAUDO, P. FINOCCHINARO and S. CACCOMESE, J. Polymer Sci. 9, A - I : 3627, 1971 13. M. G. KRAKOVYAK, Ye. V. ANUFRIEVA, M. V. VOL'KENSHTEIN, T. D. ANAN'EVA, Yu. Ya. GOTLIB, R. A. GROMOVA, S. P. KOZEL, G. I. LASHKOV, V. B. LUSH{~I]~, V. D. PAUTOV, S. S. SKOROKHODOV a n d T. V. SHEVELEVA, Dokl. A k a d . N a u k ~SSR 224: 873, 1975 14. F. H. STEWART, Autral. J. Chem. 13: 478, 1960 15. E. BERLINER and N. SHIEH, J. Am. Chem. Soc. 79: 3849, 1957 16. G. M. BADGER and R. S. PEARCE, J. Chem. See., 2317, 1950 17. A. L. B E C K A W I T H and W . A. WATERS, J. Chem. See., 1901, 1957 18. E. G. HAWKINS, J. Chem. See., 3858, 1957 19. I. P. FISCHER, Makromol. Chemie 155: 211, 1972 20. V. B.LUSHCHIK. a n d S. S. SKOROKHODOV, Vysokomol. soyed. B18: 421, 1971 (Not translated in Polymer Sci. U.S.S.R.)

STUDY OF THE SUPERMOLECULAR ORGANIZATION IN FILMS OF CELLULOSE DERIVATIVES* S~. TuICHI~.V, N. SULT~OV, D. RASHIDOV, Y~.. T. ~/L~GDALEVand B. M. Gr~ZBURO H i g h Polymers Institute, U.S.S.R. A c a d e m y of Sciences (Received 9 J u n s 1975) X - r a y methods have been used to s t u d y the supermoleeular organization in cellulose triacetate, cellulose diacetate a n d nitrocellulose films. The samples stretched b y 100~/o a t 140-150°C d i d n o t yield small angle reflexions although a well developed * Vysokomol. soyed. A18: No. 7, 1498-1502, 1976.

S'K. TUICHIEV et al.

crystalline order existed. The elasticity moduli E~' have been determined for the cellulose triacetate crystal lattice and showed the E~' for stretching in direction of the macromolecular axis to be larger by one order magnitude than the macroscopic elasticity modulus of the sample; its deformation was always larger than that of the crystal, which means that alternation of less rigid with rigid segments exists, even though the small angle reflexions are absent, and that these segments form the basis of the larger periods appearing after t~mpering (at 200-250°C) as intense meridian reflexions on the small angle X-ray pictures (SAX). The width of the fibrils in the orientated sample was 2-3 times that of the lateral crystal dimensions according to the X-ray data. SYNTHETIO amorphous-crystalline polymers are characterized b y the presence of the so called large periods which become particularly distinct in highly orientated systems [1, 2]. I t had not been possible until recently to establish the presence of the long periods for a number of samples from amongst such polymers with a n y reliability. To such polymers belong particularly the various cellulose derivatives. The long period is at the same time a characteristic which is v e r y sensitive to various external effects; its s t udy is therefore one of the fruitful methods of examining the supermolecular organization of polymers [1-7]. Th e long periods present in highly orientated systems which appear in the X - r a y pictures make it possible to get some information about the size of these periods as well as of the elasticity of the amorphous regions in comparable experiments [13], also about the shape of the crystals and their changes [4], the lateral dimensions of the fibrils [5-7], etc. The aim of the work described here was to examine the appearance of the long period after orientation and tempering of the films of cellulose derivatives by X-rays and to use the results to establish additional data about the structure of the samples. EXPERIMENTAL

Films of industrial samples of ceUulose triaeetatc (CTA), nitrooell~ose (~C) and cellulose diacetate (CDA) were prepared in the laboratory from 0.5% dioxane or eyelohexanone

solutions by pouring. The films were 0.2-0.3 mm thick; the initial non-orientated and the samples stretched at 140-150°C by 100% were tempered in the clamped state in air at incubator temperatures of T0~150, 180, 210 and 250°C. The tempering time varied in the range 1 rain-6 hr. The X.ray studies were at small and wide angles (SAX and LAX) in the standard instruments KRI~'-I and URS.50I, using lqi-filtered CuK~ radiation. The film deformation was measured at 0-2% precision by means of the iKIR-12 measuring microscope. RESULTS

Th e experimental results were qualitatively the same for all the sample shapes; we shall therefore make a detailed examination of only the CTA samples. Figure 1 reproduces the intensity distribution curves of the L A X and SAX

1717

Supermolecular organization in films of cellulose derivatives

scattering for non-orientated CTA samples as a function of the tempering temperature To. Although only diffuse halos are evident on the curves for the original samples (Fig. la), the X-ray diffraction pictures showed three weak rings for the interlattice distances of 10.4, 5.2 and 4.0 A. Several hours of tempering resulted in crystallization and this showed up on the L A X as an increase in the number of sharp reflexions, of their intensity, and in a reduction of the half-width (Fig. la). I, imp~sea 15

1o

,~

b

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i

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Fro. 1. a--LAX; b--SAX scattering pictures from non-orientated original films of.. 1--CTA; 2--films heated to: 2--150; 3--180; 4--210°C for 6 hr. The SAX measurements showed the original CTA samples to have a low scattering capacity (Fig. lb). A T o elevation to 180°C results in more diffuse SAX scattering (Fig. lb); this could be due to crystallization, i.e. the creation of hetero-phase fluctuations. The crystallinity is obviously still low at the cited T0 so that no discrete SAX reflexions will appear. A To elevation to 210°C resulted in the appearance of a ridge or inflexion on the SAX curves at an angle ~ = 1 8 - 2 4 ' ; this corresponds to a large period (considering the slit collimation) of about 150-210 •. The preliminary orientation of the amorphous film samples results in a stronger effect of the subsequent tempering on the structure. The stretching at 140-150°C produced in the L A X pictures a fairly large number of independent reflexions; their intensity increased with the T o elevation (Fig. 2a). The crystal dimensions also became larger (see Table). While the SAX curves show only diffuse scattering for the original orientated samples, tempering produced at first a ridge and afterwards a distinct reflexion for a period of about 235 A (Fig. 2b). The SAX reflexions appear as a result of crystallization, b u t also of thermal decomposition; the latter most probably occurs in the amorphous regions and thb

SH. Tuzcm~v e* (d.

1718

resulting weight loss (see Table) could enhauce the density difference between the crystalline and amorphous regions. Electron microscopy [8] had shown a high-temperature CTA-fibre tempering t o give rise t o a d i s t i n c t l y fibrillar s t r u c t u r e . T h e p r e s e n c e of discrete reflexions S O M E O F ~MJ$ S T R U C T U R A L P A R A M E T E R S O F T H E S T U D I E D S A ~ i ~ L E S

Structural parameters original Crystal height, /~, .A. Crystal width, /5c, .~ Width of fibril, D, A Large period, d, A Weight loss, ~o

50 45

CTA Tempering temp., °0 150 180 210 65

60

0

80 60 160 235 8

100 80 180 235 13-15

I

OI)A

t

200

!VO 140

m

35 60

45 180 230

200 300

in the SAX pictures of our samples enabled one to compare the lateral dimensions of the fibrils (or the regions of coherent SAX scattering) with those of the crystals which had been determined from the equatorial reflexion width in LAX scattering

pictures. The width of the fibrils was determined by tilting the sample relative to the primary radiation source, as described by Gerasimov and Tsvankln [5] (see also I, Lnp/sec 2U-

cL

5

~5

b

10

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I

10

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20

2 8, degrees ofangle

0

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20 ~0 ~, rain of an~ale

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FIG. 2. a - - Equatorial LAX; b-- meridian SAX scattering curves recorded on 1-- GTA samples stretched ~t 140-150°0; 2--tempered at (°C): 2--150, 3--180, 4--210, 5-250, for (hours): 1-4--6; 5--0-5.

Supermolecular organization in films of cellulose derivatives

1719

ref. 6 and 7 for uses of the method). The fibrillar dimensions were found to be 2-3 times larger than the lateral dimension (width) of the crystals in all cases (see Table). Similar results were also got for various polymer fibres [7]. r, ~rap

a

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18"7

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I0000

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2B FIG. 3. The displacement of the reflexion contour at: a--the first, b--the third layer line on applying stress to the CTA sample in direction of the orientation axis. a, kgf/mml: 1--0; 2--3.5; 3--7.7. We presume that the long period structure corresponds to alternating erystMline and amorphous regions of various rigidities for the purpose of the mechanics of these substances. This will be specifically evident as a E~ value determined from the meridian SAX reflexion shift when stress is applied to the samples in direction of the axis of orientation and exceeds the elasticity modulus of the sample as a whole, i.e. E~ [9]. The SAX reflexion changes during the elastic deformation of orientated polymer showed at the same time that the rigidity of ~he amorphous regions is much lower than that of the sample [2]. tempering at To giving rise to discrete as well as sharp reflexions of the

1720

SH. Tuicm3~v et: al.

SAX pictures unf or t una t e l y caused the films to become brittle and warped, so t h a t precise X - r a y measurements could not be made of samples under loadi Like Sakurada and co-workers [9], we therefore determined E c on samples subjected at 140-150°C only to orientating stretching which was followed b y t h er mal fixing a t 150°C. The meridian reflexion shifts of the first and third layer lines (Fig. 3) were used for this purpose together with slit collimation of t h e p r i m a r y beam. The slopes of the stress-deformation curves were used to determine the elastici t y modulus of the sample as a whole, E~. Identical deformation stress applied t o the sample always caused larger deformations of the crystal; the E~ was always larger b y one pot ency t h a n the E o. An E c = 3 3 0 0 - 3 8 0 0 for the crystal lattice gave an E g = 1 6 0 - 2 0 0 k g f / m m 2 for the sample, while the Ecx-~180-220 and the E ~ = 4 0 - - 5 O k g f / m m 2 (the sample was stretched at 140-150°C). This means t h a t even when a sample does not produce an SAX reflexion there are more or less rigid alternating regions present in it as the main structural components of the long periods which become visible after high temperature tempering. The heterogeneity in lateral direction becomes apparent in the same manner: t h e (310) equatorial reflexion shift at stress normal to the orientation axis will give the elasticity modulus Ecx which was found to be 4-5 times larger t han t h a t of t h e sample as a whole, i.e. E~. Translated by K. A. ALLE~< REFERENCES

1. B. KI (Ed.), ~qoveishie metody issledovaniya polimerov (Recent Polymer Investigation Methods). Izd. "Mir", 1966 2. D. Ya. TSVANK1N, Dissertation, 1970 3. A. I. SLUTSKER, Dissertation, 1968; A. A. YASTREBINSKII, Dissertation, 1965; S. N. ZlZlURKOV, A. I. SLUTSKER and A. A. YASTI~EBINSKII, Dokl. ~4kad. Nauk SSSR 153: 303, 1963; V. S. ]KUKSENKO and A. I. SLUTtKER, Fiz. tverd, tela 1O: 838, 1968 4. V. I. GERASLMOV and D. Ya. TSVANKIN, Vysokornol soyed. All: 2652, 1969 (Translated in Polymer Sei. U.S.S.R. U: 12, 3013, 1969) 5. B. S. BEAR and O. E. A. BOLIDUAN, J. Polymer Sei. 6: 271, 1951 6. M. A. CEZALOV, V. S. KUKSENKO and A. I. SLUTSKER, Vysokcmol. soyed. A12: 1787, 1970 (Translated in Pol~rr.er $ci. U.S.S.I~. 12: 8, 2~27, 1970) 7. Yu. V. BRESTKIN, B. M. GINZBURG, P. A. IL'CHE~KO, M. A. MARTYNOV, Sh. TUICHIEV and S. Ya. ~RENKEL, Vysckcraol. soyed. A15: 621, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 3, 702, 1973) 8. A. M. HINDEL]EH and D. J. JOHNSON, Polymer 9: 7, 1972 9. I. SAIKURADA, T. ITO and lg. NAKAMAE, Khim. tekh. polimerov, 19, 1964; L SAKURADA, Y. ITO and K. NAKAMAE, J. Polymer Sei. C15: 75, 1966; I. SAKURADA and K. KAJI, J. Polymer Sci. C31: 57, 1970