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Study of the electronic spectra of dialdehydecellulose
1900
M. Z. GAVRILOVand I. N. Y ~ M o ~ o
9. V. N. TSVETKOV, Vysokomol. soyed. 5: 570, 1963 10. T. M. BIRSHTEIN, V. P. BUDTOV, E. V. FRISMAN and N. K. YANOVSKAYA, Vysoko. mol. soyed. 4: 455, 1962 (Not translated in Polymer Sci. U.S.S.R.) 11. V. N. TSVETKOV and L. N. VERKHOTINA, Zh. tekhn fiz. 28: 273, 1958 12. E. V. FRISMAN and N. N. BOITSOVA, Vestnik Leningrad State University 4: 26, 1959
STUDY OF THE ELECTRONIC SPECTRA OF DIALDEHYDECELLULOSE * M. Z. GXVRmOV and I. N. YERMOLENKO Institute of General and Inorganic Chemistry, Beloruss. S.S.R. Academy of Sciences (Received 6 June 1966)
VIBRATIO~ spectra measured under normal conditions show t h a t there are practically no free aldehyde groups in dialdehydecellulose (DAC) [1-3]. Judging b y the apl~arance of the absorption band of the C ~ O groups in the region of 5.8 p t h e y emerge only when the samples are carefully dried [2, 4-6]. I t was suggested [1-8] t h a t in the presence of water in DAC most of the aldehyde groups are hydrated and form hemiacetal and hemialdal bonds [1-8]. The structures I - V I of the elementary units of I)AC macromolecules which are in reversible equilibrium depending on the water content are depicted below. Structures of types I I - V are also possible between the units of adjacent macromoleeuies, in which case t h e y form "bridge" bonds. H I C •"-,,c/6~
OH I C ~\~,H
.I
,, I
CH43H ....... /
p ~ c c
\H I-I/ ~ ~H
%
_
...\ /k~O H/%/H
-CH2OH
OH /H H OH c c H ""\ / ~ _ / ~ / C H 0 c V ,
CH20H
H\ o~ / OH \ /OH
/ 'o
C G •..\ / 'OH, \ , ~
..
o,
CH2
2 %H/OH ...\ /Cx HH/C\ /H
H K~
,,...
CH~
O/
o...
I CHzOH
* Vysokomol. soyed. Ag: No. 8, 1688-1692, 1967.
OH OHOH OH ~c" 'c" ...k/ \ /H. "c \H H/
"/\C
O/\o'''cVII
CH2OH
Electronic spectra of dialdehydecellulose
1901
Assuming the presence of such structures and t h a t the UV absorption of DAC is due to free aldehyde groups, variations in the c o n t e n t of the latter during h y d r a t i o n or d e hydr at i on m us t be reflected in changes in the electronic spectra. The aim o f the authors was to s t u d y the electronic absorption spectra of I)AC an d some of the luminescence characteristics of DAC in relation to t he equilibrium water v a p o u r pressure above it. The hydroeellulose (HC) and cotton cellulose (chromatographic paper) were purified by the usual methods and oxidized for 6 hr until dialdehyde cellulose was obtained by the method described in [9] under conditions ensuring the accumulation of 4-5~ of CHO groups in the composition of the product. After oxidation the samples were carefully washed with water and dried in air. To measure the spectra the samples were placed in hermetically sealed closed cells made of optical fused quartz glass. The desiccating agents were anhydrous perchlorate of magnesium, and to create relative humidities of 32 and 80~ in the cells saturated aqueos solutions of calcium chloride and urea were used and placed at the bottom of a quartz cell. To avoid degradative changes in the polymer the method of drying by heating used in [5] was not adopted. To measure the spectra in luminescence, the absorption spectra, the luminescence excitation spectra and the relations of the relative quantum yield of luminescence to the wave. length of the exciting radiation, the methods described in [10, I1] were used.
0"5
I
200
I
300
~
I
400
I
I
500 /], m~
FIG. 1. Absorption spectra of HC and I)AC, also the luminescence spectra and luminescence excitation spectrum and the relation of the relative quantum yield of luminescence to the wavelength of the exciting radiation (designations in text). Figure 1 shows the absorption spectra of the HC film oxidized with calcium periodate in relation to the equilibrium relative water v a p o u r pressure (P) in the amb ien t atmosphere. Figure 1 shows t h a t when P = 8 0 % there is no absorption band in the region of 3000 m/~ in the spettr am of DAC (curve 1), while under normal conditions (when P = 3 2 % ) there is a weak absorption band in this region (curve 2). However in th e region of 200-220 m/z decrease in h u m i d i t y is accompanied b y a considerable increase in absorption the magnitude of the increase being proportional to reduction in t he wavelength. Thus in the region of 200 m/~ the absorption intensity for DAC when/7-----32% is approximately twice t h a t for the samples when P = 8 0 % . Drying at room t e m per a t ur e results in still more intense absorption
1902
1~. Z. GAVRILOVand I. 1~. YERMOLEI~-~O
in these regions of the spectrum (curve 3). At the same time a well-defined absorption band appears in the region of 300 m/~ and the absorption intensity in the region of 200-220 m/~ is more than twice that for the moistened samples. The effect is reversible. These results agree with current theories regarding changes in aldehyde groups during drying and moistening, and indicate that the absorption in the UV region is mainly due to the less hydrated structures, including the aldehyde groups. B y analogy with low-molecular aliphatie aldehydes [12] an absorption band in the region of 300 m/~ is probably due to a forbidden n->~* transition of the aldehyde groups, and in the region of 200-220 m~ to the permitted n-~a* transition of these same groups. The short-wavelength absorption maximum is in the region of 2 < 2 0 0 rag, which is outside the measuring range of ordinary quartz spectrophotometers. There is a plateau in the absorption spectrum of the DAC in the region of 245 m/~ which is difficult to assign on the basis of present data. The correct assignment of the DAC absorption is confirmed b y the moistureindependence of the absorptive capacity of samples which do not contain a considerable number of aldehyde groups. The absorption spectra of the dried (4) and moistened (5) unoxidized tIC are shown as an example in Fig. 1 (curves 4 and g). These results show that the electronic absorption spectra are considerably more sensitive to the less hydrated structures, including the aldehyde groups, than the vibration spectra [4-6], and this could provide a possible basis for a method of determining the aldehyde groups in DAC. Figure 1 (curves 6-8) shows the characteristic luminescence spectra of the same DAC samples under normal conditions; the spectra were obtained b y averaging several spectra for different samples. Depending on the wavelength of the exciting radiation three bands appear in the luminescence spectrum. Thus on excitation with a 280 mg line the maximum of the basic most intense line is in the region of 450-460 m# (curve 6). At the same time in the region 400 and 500 m/~ there are two less intense bands greatly overlapped b y the main band and appearing in plateau form in the spectrum. A similar spectrum is obtained on excitation with a 265 m# line also. Excitation with lines of 297, 303 and 313 m# causes luminescence spectra in which the band with maximum at 400 m/l is the most intense (curves 7 and 8). At the same time the band in the region of 500 m/l appears in the spectrum as a plateau only on excitation with lines of 297 and 303 rag. The band with a maximum in the region of 450-460 mg is greatly oxerlapped b y the main band at 400 m~ and this causes a slight displacement of its maximum in the longwave direction. On excitation with a 365 mz line the maximum of the most intense luminescence spectrum is in the region of 450-460 m/~ (curve 9), which agrees with the data in [13]. In the region of 500 m/~ there is at the same time a band in the form of a plateau. Similar luminescence spectra on excitation with a 365 m/~ line appear also in initial and in acetylated celluloses [10-11] and are probably of the same nature. The luminescence spectra of DAC based on cotton cellulose are of a similar
Electronic spectra of dialdehydecellulose
1903
nature. The extremely slight differences in the spectra appear only in the relative intensities of the separate bands. In view of the effect of the wavelength of the exciting radiation on the luminescence spectra of DAC, shown b y the appearance of three luminescence bands, it m a y be assumed t h a t there are several types of luminescence centres in DAC. The free aldehyde groups are related to one of these types of centres. Since excitation with lines of 297, 303 and 313 mp which are in the region of the absorption band assigned above to less hydrated structures with the participation of aldehyde groups, results in the appearance of an intense band with a maximum in the region of 400 m/~ in the luminescence spectrum, it m a y be assumed t h a t this band is due to the emission of these very groups. I t was suggested in [10] that when luminescence of the initial cellulose materials was excited with a 313 m/~ line the spectrum consists of three overlapping bands. As there are always an appreciable number of aldehyde groups in the initial cellulose, we m a y assume that they also make their contribution, b u t its luminescence spectrum should be taken as consisting not of three, b u t of a large number of bands. The disagreement in the position of the peaks in the spectra for DAC and the initial cellulose (400 and 430-440 m/~) on excitation with a 313 m/~ line m a y be explained by the difference in their content of aldehyde groups causing differences in the relative intensities of the separate luminescence bands. The band with a maximum in the region of 450-460 m/l m a y be assigned to the emission of luminescence centres of the second type; this band appears clearly on excitation with a 365 nap line. There arc no well defined absorption bands in the region of 365 m/~. To determine the region of active absorption causing the emission of the band with a maximum at 400 m]~ its excitation spectrum was obtained b y means of measurements the intensity in the peak. A well-defined band with a maximum in the region of 320 m/~ (Fig. 1, cm~re 10) appears in it. A similar band appears also in the excitation spectrum determined from the integral intensities of the luminescence spectrum. The presence in the excitation spectrum of a band in the region of the long-wavelength absorption of aldehyde groups agrees with the assignment of the absorption band and luminescence band made above. The insignificant disagreement of the peaks of bands in the excitation spectrum ( ~ a x = 3 2 0 nap) and absorption spectrum (2max= 300 m/~) m a y be explained b y the fact that the long-wavelength edge of inactive absorption with a maximum in the region of 245 m/l appearing in the spectrum in the form of a plateau is superimposed on a short-wavelength absorption edge with a maximum at 300 m/~. The overlapping of these two bands causes long-wavelength displacement of the band in the excitation spectrum. The low activity of the absorption band at 245 m/~ shows also that the luminescence intensity of DAC on excitation in this region of the spectrum (2<265 rap) is so low that the luminescence spectrum cannot be recorded with the apparatus we were using. The dependence of the relative quantum yield of luminescence on the wave-
1904
M. Z. GAVRILOVand I. N. YERMOLENKO
length of the exciting' radiation, measured through the integral intensities of the luminescence spectra is not constant (curve 11). This is a further indication that in the UV region of the spectrum there are several absorption bands related to different centres and differing as to their quantum yields of luminescence. The relative quantum yield was calculated from the luminescence excitation spectrum b y introducing into the latter corrections for the samples under investigation. A similar excitation spectrum for the luminescence band due to the irradiation of aldehyde groups is characteristic of DAC based on cotton cellulose. Its U V absorption spectrum is also similar to the spectrum for DAC based on ~IC [14]. It is known that there is a linear relation between the luminescence intensity and the concentration of radiation centres only in the absence of extinction Extinction m a y be due to several factors, e.g. if the concentration of the centres themselves in increased beyond a certain limit, or if the concentration of impurities, including sorbed components, is increased.
3 3
J50
45g
55g ~ #
FIG. 2. Relation of 1-m~uescence spectra of DAC to humidity on excitation with 313 mlJ line: Humidity, ~o/--0; 2--32; 3--80. ,ks during the drying of DAC samples the intensity of the a b s o r p t i o n b a n d due to aldehyde groups (as was stated above) increases it was desired to study the humidity dependence of the intensity of the corresponding luminescence band. The tests showed that the drying of D•C samples reduces t h e intensity of the luminescence band at 400 m/~ assigned to the emission of aldehyde group. This is illustrated in Fig. 2 showing the moisture dependence of the relative intensity* of the luminescence band of DAC based on cotton cellulose. This somewhat unexpected result calls for further investigation. * In measuring the luminescence intensities of DAC relative to humidity a control sample with moisture-independent luminescence properties, lumogene bright yellow, was used. This moisture-independence of its luminescence was verified by comparison with the intensity of uranyl glass.
Electronic spectra o f dialdehydecellulose
1905
Together with the rise in the intensity of the luminescence band at 400--410 m/l accompanying moistening there is also a rise in the luminescence band with a maximum at 450-460 nap which appeared on excitation with the 365 m~ line. This effect is reversible. Repeated moistening, followed by drying, reduces the intensities of the corresponding bands. However the luminescence band with a maximum at 500 m/~ is weakly dependent on moisture. The different sensitivity of the separate luminescence bands of DAC to the a m o u n t of adsorbed water casses considerable changes in the shape of the spectra on excitation by different wavelengths. Therefore even the luminescence excitation spectra are weakly dependent on humidity. All these changes arc in accordance with the view t h a t there are several centres of luminescence differing in regard to extinction when moistened, and t h a t corresponding changes occur in the concentration of the given structures. CONCLUSIONS
(1) :By studying the dependence of the absorption spectra of ]:)AC on humidity it has been shown t h a t absorption in the region of 200-220 nap and a band in the region of 300 m/l are due to free aldehyde groups. (2) The dependence of the UV absorption on h u m i d i t y could provide a basis for a method of detecting aldehyde groups and determining their number. (3) I n the luminescence spectrum of DAC there are three bands with peaks at 400, 450-460 and 500 rap, and the ratio of their intensities depends on the wavelength of the exciting radiation, which indicates t h a t there are several types of centres of emission. (5) The agreement of the absorption spectra of DAC with the excitation spectra of the luminescence band at 400 mp shows t h a t the latter is due to the emission of free aldehyde groups. The absorption in the region of 245 m/~ is nonactive. Translated by R. J. A. HENDRY REFERENCES 1. J. W. ROWEN, E. H. FORZIATI and R. E. REEVES, J. Amer. Chem. Soc. 73: 4484, 1961 2. I. N. YERMOLENKO, Spektroskopiya ~' khimii okislennykh cellyuloz (Spectroscopy in the Chemistry of Oxidized Celluloses). Izd. Akad. Nauk BSSR, 1959 3. R. G. ZHABANKOV, Infrakrasnye spektry cellulozy i eye proizvodnykh (Infrared Spectra of Cellulose and its Derivatives). Izd. "Nauka i tekhnika", 1964 4. H. G. HIGGINS and A. S. MCKENZIE, Austral. J. Appl. Sci. 9: 167, 1958 5. H. SPEDDING, J. Chem. Soc., 3147, 1960
6. O. ANT-WUORINEN and A. VISAPAA, Tied. ¥oltiontekn. tutkimuslaitos 4: 21, 1963 7. V. I. IVANOV, I. N. YERMOLENKO, S. S. GUSEV, N. Ya. LENSHINA and V. S. IVANOVA
Izv. Akad. Nauk SSSR, odt. khim. n., No. 12, 2249, 1960 8. I. N. YERMOLENKO, R. G. ZHBANKOV, V. I. IVANOV, N. Ya. LENSHINA and V. S.
IVANOVA, Izv. Akad. Nauk odt. khim. n., No. 2, 249, 1958 9. Z. I. KUZNETSOVA, V. S. IVANOVA and N. N. SHORYGINA, Izv. Akad. Nauk odt. khim. n., No. 9, 1886, 1963 10. M. Z. GAVRILOV and I. N. YERMOLENKO, Zh. prikl, spektroskopii 5: 762, 1966
1906
A. SH. GOIKHMAI~
11. M. Z. GAVRILOV and I. N. YERMOLENKO, Zh. prikl, spektroskopii 6: 197, 1967 12. Ch. N. R. RAO, Elektronnye spektry v khimii (Electron Spectra in Chemistry). Izd. "Mir", 1964 13. I. N. YERMOLENKO and M. Z. GAVRILOV, Reports on I Conf. on Use of Methods of Molecular Spectral Analysis (Russian), publ. by Byeloruss. State Univ., 1958 14. I. N. YERMOLENKO and M. Z. GAVRILOV, Vestnik Akad. Nauk BSSR, set. fiz.-mat. n., No. 4, 126, 1966
X-RAY
S T U D Y OF T H E O R I E N T A T I O N
DISTRIBUTION
OF C R Y S T A L L I T E S * A. SH. GOIKHMAN
Kiev Branch of the All-Union Synthetic Fibre Research Institute (Received 6 June 1966)
X-RAY scattering in a crystallite system with ideal uniaxial orientation and statistical azimuthal distribution of the crystallites (a texture with complete rotation) produces a pattern like the X-ray diagram of a rotating crystal. In this case a certain direction in the crystal, e.g. normal to hkl, makes a quite definite angle with the texture axis, and this angle is the same for all crystallites. I n a concrete case, for instance in partially oriented fibres and films, there is a certain dispersion of crystallites relative to the texture axis and the points in the X-ray diagram of the texture are blurred into arcs ("sickles") along D e b y e Sherrer rings. It is thought that the cryst~llite distribution relative to the texture axis can be estimated from the intensity distribution along these ares. Let us consider the connection between the intensity distribution for the interference of hkl with respect to the azimuthal angle J (read off the meridian in the X-ray picture of the fibre) and the distribution of the crystallites. Let us say the position of the crystallite is the direction normal to hk/--one of the many crystallographic axes. We know [1] that the integral reties intensity in an X-ray texture diagram is connected with the intensity of the same reflex in the X-ray rotation diagram of a single crystal b y the relationship
tox =Irotn/2
(1)
where Itex, trot are the integral intensities in the texture diagram and rotation diagram respectively; ~ is the number of crystallites making a contribution to "~tex °
* Vysokomol. soyed. A9: No. 8, 1693-1698, 1967.
M. Z. GAVRILOVand I. N. Y ~ M o ~ o
9. V. N. TSVETKOV, Vysokomol. soyed. 5: 570, 1963 10. T. M. BIRSHTEIN, V. P. BUDTOV, E. V. FRISMAN and N. K. YANOVSKAYA, Vysoko. mol. soyed. 4: 455, 1962 (Not translated in Polymer Sci. U.S.S.R.) 11. V. N. TSVETKOV and L. N. VERKHOTINA, Zh. tekhn fiz. 28: 273, 1958 12. E. V. FRISMAN and N. N. BOITSOVA, Vestnik Leningrad State University 4: 26, 1959
STUDY OF THE ELECTRONIC SPECTRA OF DIALDEHYDECELLULOSE * M. Z. GXVRmOV and I. N. YERMOLENKO Institute of General and Inorganic Chemistry, Beloruss. S.S.R. Academy of Sciences (Received 6 June 1966)
VIBRATIO~ spectra measured under normal conditions show t h a t there are practically no free aldehyde groups in dialdehydecellulose (DAC) [1-3]. Judging b y the apl~arance of the absorption band of the C ~ O groups in the region of 5.8 p t h e y emerge only when the samples are carefully dried [2, 4-6]. I t was suggested [1-8] t h a t in the presence of water in DAC most of the aldehyde groups are hydrated and form hemiacetal and hemialdal bonds [1-8]. The structures I - V I of the elementary units of I)AC macromolecules which are in reversible equilibrium depending on the water content are depicted below. Structures of types I I - V are also possible between the units of adjacent macromoleeuies, in which case t h e y form "bridge" bonds. H I C •"-,,c/6~
OH I C ~\~,H
.I
,, I
CH43H ....... /
p ~ c c
\H I-I/ ~ ~H
%
_
...\ /k~O H/%/H
-CH2OH
OH /H H OH c c H ""\ / ~ _ / ~ / C H 0 c V ,
CH20H
H\ o~ / OH \ /OH
/ 'o
C G •..\ / 'OH, \ , ~
..
o,
CH2
2 %H/OH ...\ /Cx HH/C\ /H
H K~
,,...
CH~
O/
o...
I CHzOH
* Vysokomol. soyed. Ag: No. 8, 1688-1692, 1967.
OH OHOH OH ~c" 'c" ...k/ \ /H. "c \H H/
"/\C
O/\o'''cVII
CH2OH
Electronic spectra of dialdehydecellulose
1901
Assuming the presence of such structures and t h a t the UV absorption of DAC is due to free aldehyde groups, variations in the c o n t e n t of the latter during h y d r a t i o n or d e hydr at i on m us t be reflected in changes in the electronic spectra. The aim o f the authors was to s t u d y the electronic absorption spectra of I)AC an d some of the luminescence characteristics of DAC in relation to t he equilibrium water v a p o u r pressure above it. The hydroeellulose (HC) and cotton cellulose (chromatographic paper) were purified by the usual methods and oxidized for 6 hr until dialdehyde cellulose was obtained by the method described in [9] under conditions ensuring the accumulation of 4-5~ of CHO groups in the composition of the product. After oxidation the samples were carefully washed with water and dried in air. To measure the spectra the samples were placed in hermetically sealed closed cells made of optical fused quartz glass. The desiccating agents were anhydrous perchlorate of magnesium, and to create relative humidities of 32 and 80~ in the cells saturated aqueos solutions of calcium chloride and urea were used and placed at the bottom of a quartz cell. To avoid degradative changes in the polymer the method of drying by heating used in [5] was not adopted. To measure the spectra in luminescence, the absorption spectra, the luminescence excitation spectra and the relations of the relative quantum yield of luminescence to the wave. length of the exciting radiation, the methods described in [10, I1] were used.
0"5
I
200
I
300
~
I
400
I
I
500 /], m~
FIG. 1. Absorption spectra of HC and I)AC, also the luminescence spectra and luminescence excitation spectrum and the relation of the relative quantum yield of luminescence to the wavelength of the exciting radiation (designations in text). Figure 1 shows the absorption spectra of the HC film oxidized with calcium periodate in relation to the equilibrium relative water v a p o u r pressure (P) in the amb ien t atmosphere. Figure 1 shows t h a t when P = 8 0 % there is no absorption band in the region of 3000 m/~ in the spettr am of DAC (curve 1), while under normal conditions (when P = 3 2 % ) there is a weak absorption band in this region (curve 2). However in th e region of 200-220 m/z decrease in h u m i d i t y is accompanied b y a considerable increase in absorption the magnitude of the increase being proportional to reduction in t he wavelength. Thus in the region of 200 m/~ the absorption intensity for DAC when/7-----32% is approximately twice t h a t for the samples when P = 8 0 % . Drying at room t e m per a t ur e results in still more intense absorption
1902
1~. Z. GAVRILOVand I. 1~. YERMOLEI~-~O
in these regions of the spectrum (curve 3). At the same time a well-defined absorption band appears in the region of 300 m/~ and the absorption intensity in the region of 200-220 m/~ is more than twice that for the moistened samples. The effect is reversible. These results agree with current theories regarding changes in aldehyde groups during drying and moistening, and indicate that the absorption in the UV region is mainly due to the less hydrated structures, including the aldehyde groups. B y analogy with low-molecular aliphatie aldehydes [12] an absorption band in the region of 300 m/~ is probably due to a forbidden n->~* transition of the aldehyde groups, and in the region of 200-220 m~ to the permitted n-~a* transition of these same groups. The short-wavelength absorption maximum is in the region of 2 < 2 0 0 rag, which is outside the measuring range of ordinary quartz spectrophotometers. There is a plateau in the absorption spectrum of the DAC in the region of 245 m/~ which is difficult to assign on the basis of present data. The correct assignment of the DAC absorption is confirmed b y the moistureindependence of the absorptive capacity of samples which do not contain a considerable number of aldehyde groups. The absorption spectra of the dried (4) and moistened (5) unoxidized tIC are shown as an example in Fig. 1 (curves 4 and g). These results show that the electronic absorption spectra are considerably more sensitive to the less hydrated structures, including the aldehyde groups, than the vibration spectra [4-6], and this could provide a possible basis for a method of determining the aldehyde groups in DAC. Figure 1 (curves 6-8) shows the characteristic luminescence spectra of the same DAC samples under normal conditions; the spectra were obtained b y averaging several spectra for different samples. Depending on the wavelength of the exciting radiation three bands appear in the luminescence spectrum. Thus on excitation with a 280 mg line the maximum of the basic most intense line is in the region of 450-460 m# (curve 6). At the same time in the region 400 and 500 m/~ there are two less intense bands greatly overlapped b y the main band and appearing in plateau form in the spectrum. A similar spectrum is obtained on excitation with a 265 m# line also. Excitation with lines of 297, 303 and 313 m# causes luminescence spectra in which the band with maximum at 400 m/l is the most intense (curves 7 and 8). At the same time the band in the region of 500 m/l appears in the spectrum as a plateau only on excitation with lines of 297 and 303 rag. The band with a maximum in the region of 450-460 mg is greatly oxerlapped b y the main band at 400 m~ and this causes a slight displacement of its maximum in the longwave direction. On excitation with a 365 mz line the maximum of the most intense luminescence spectrum is in the region of 450-460 m/~ (curve 9), which agrees with the data in [13]. In the region of 500 m/~ there is at the same time a band in the form of a plateau. Similar luminescence spectra on excitation with a 365 m/~ line appear also in initial and in acetylated celluloses [10-11] and are probably of the same nature. The luminescence spectra of DAC based on cotton cellulose are of a similar
Electronic spectra of dialdehydecellulose
1903
nature. The extremely slight differences in the spectra appear only in the relative intensities of the separate bands. In view of the effect of the wavelength of the exciting radiation on the luminescence spectra of DAC, shown b y the appearance of three luminescence bands, it m a y be assumed t h a t there are several types of luminescence centres in DAC. The free aldehyde groups are related to one of these types of centres. Since excitation with lines of 297, 303 and 313 mp which are in the region of the absorption band assigned above to less hydrated structures with the participation of aldehyde groups, results in the appearance of an intense band with a maximum in the region of 400 m/~ in the luminescence spectrum, it m a y be assumed t h a t this band is due to the emission of these very groups. I t was suggested in [10] that when luminescence of the initial cellulose materials was excited with a 313 m/~ line the spectrum consists of three overlapping bands. As there are always an appreciable number of aldehyde groups in the initial cellulose, we m a y assume that they also make their contribution, b u t its luminescence spectrum should be taken as consisting not of three, b u t of a large number of bands. The disagreement in the position of the peaks in the spectra for DAC and the initial cellulose (400 and 430-440 m/~) on excitation with a 313 m/~ line m a y be explained by the difference in their content of aldehyde groups causing differences in the relative intensities of the separate luminescence bands. The band with a maximum in the region of 450-460 m/l m a y be assigned to the emission of luminescence centres of the second type; this band appears clearly on excitation with a 365 nap line. There arc no well defined absorption bands in the region of 365 m/~. To determine the region of active absorption causing the emission of the band with a maximum at 400 m]~ its excitation spectrum was obtained b y means of measurements the intensity in the peak. A well-defined band with a maximum in the region of 320 m/~ (Fig. 1, cm~re 10) appears in it. A similar band appears also in the excitation spectrum determined from the integral intensities of the luminescence spectrum. The presence in the excitation spectrum of a band in the region of the long-wavelength absorption of aldehyde groups agrees with the assignment of the absorption band and luminescence band made above. The insignificant disagreement of the peaks of bands in the excitation spectrum ( ~ a x = 3 2 0 nap) and absorption spectrum (2max= 300 m/~) m a y be explained b y the fact that the long-wavelength edge of inactive absorption with a maximum in the region of 245 m/l appearing in the spectrum in the form of a plateau is superimposed on a short-wavelength absorption edge with a maximum at 300 m/~. The overlapping of these two bands causes long-wavelength displacement of the band in the excitation spectrum. The low activity of the absorption band at 245 m/~ shows also that the luminescence intensity of DAC on excitation in this region of the spectrum (2<265 rap) is so low that the luminescence spectrum cannot be recorded with the apparatus we were using. The dependence of the relative quantum yield of luminescence on the wave-
1904
M. Z. GAVRILOVand I. N. YERMOLENKO
length of the exciting' radiation, measured through the integral intensities of the luminescence spectra is not constant (curve 11). This is a further indication that in the UV region of the spectrum there are several absorption bands related to different centres and differing as to their quantum yields of luminescence. The relative quantum yield was calculated from the luminescence excitation spectrum b y introducing into the latter corrections for the samples under investigation. A similar excitation spectrum for the luminescence band due to the irradiation of aldehyde groups is characteristic of DAC based on cotton cellulose. Its U V absorption spectrum is also similar to the spectrum for DAC based on ~IC [14]. It is known that there is a linear relation between the luminescence intensity and the concentration of radiation centres only in the absence of extinction Extinction m a y be due to several factors, e.g. if the concentration of the centres themselves in increased beyond a certain limit, or if the concentration of impurities, including sorbed components, is increased.
3 3
J50
45g
55g ~ #
FIG. 2. Relation of 1-m~uescence spectra of DAC to humidity on excitation with 313 mlJ line: Humidity, ~o/--0; 2--32; 3--80. ,ks during the drying of DAC samples the intensity of the a b s o r p t i o n b a n d due to aldehyde groups (as was stated above) increases it was desired to study the humidity dependence of the intensity of the corresponding luminescence band. The tests showed that the drying of D•C samples reduces t h e intensity of the luminescence band at 400 m/~ assigned to the emission of aldehyde group. This is illustrated in Fig. 2 showing the moisture dependence of the relative intensity* of the luminescence band of DAC based on cotton cellulose. This somewhat unexpected result calls for further investigation. * In measuring the luminescence intensities of DAC relative to humidity a control sample with moisture-independent luminescence properties, lumogene bright yellow, was used. This moisture-independence of its luminescence was verified by comparison with the intensity of uranyl glass.
Electronic spectra o f dialdehydecellulose
1905
Together with the rise in the intensity of the luminescence band at 400--410 m/l accompanying moistening there is also a rise in the luminescence band with a maximum at 450-460 nap which appeared on excitation with the 365 m~ line. This effect is reversible. Repeated moistening, followed by drying, reduces the intensities of the corresponding bands. However the luminescence band with a maximum at 500 m/~ is weakly dependent on moisture. The different sensitivity of the separate luminescence bands of DAC to the a m o u n t of adsorbed water casses considerable changes in the shape of the spectra on excitation by different wavelengths. Therefore even the luminescence excitation spectra are weakly dependent on humidity. All these changes arc in accordance with the view t h a t there are several centres of luminescence differing in regard to extinction when moistened, and t h a t corresponding changes occur in the concentration of the given structures. CONCLUSIONS
(1) :By studying the dependence of the absorption spectra of ]:)AC on humidity it has been shown t h a t absorption in the region of 200-220 nap and a band in the region of 300 m/l are due to free aldehyde groups. (2) The dependence of the UV absorption on h u m i d i t y could provide a basis for a method of detecting aldehyde groups and determining their number. (3) I n the luminescence spectrum of DAC there are three bands with peaks at 400, 450-460 and 500 rap, and the ratio of their intensities depends on the wavelength of the exciting radiation, which indicates t h a t there are several types of centres of emission. (5) The agreement of the absorption spectra of DAC with the excitation spectra of the luminescence band at 400 mp shows t h a t the latter is due to the emission of free aldehyde groups. The absorption in the region of 245 m/~ is nonactive. Translated by R. J. A. HENDRY REFERENCES 1. J. W. ROWEN, E. H. FORZIATI and R. E. REEVES, J. Amer. Chem. Soc. 73: 4484, 1961 2. I. N. YERMOLENKO, Spektroskopiya ~' khimii okislennykh cellyuloz (Spectroscopy in the Chemistry of Oxidized Celluloses). Izd. Akad. Nauk BSSR, 1959 3. R. G. ZHABANKOV, Infrakrasnye spektry cellulozy i eye proizvodnykh (Infrared Spectra of Cellulose and its Derivatives). Izd. "Nauka i tekhnika", 1964 4. H. G. HIGGINS and A. S. MCKENZIE, Austral. J. Appl. Sci. 9: 167, 1958 5. H. SPEDDING, J. Chem. Soc., 3147, 1960
6. O. ANT-WUORINEN and A. VISAPAA, Tied. ¥oltiontekn. tutkimuslaitos 4: 21, 1963 7. V. I. IVANOV, I. N. YERMOLENKO, S. S. GUSEV, N. Ya. LENSHINA and V. S. IVANOVA
Izv. Akad. Nauk SSSR, odt. khim. n., No. 12, 2249, 1960 8. I. N. YERMOLENKO, R. G. ZHBANKOV, V. I. IVANOV, N. Ya. LENSHINA and V. S.
IVANOVA, Izv. Akad. Nauk odt. khim. n., No. 2, 249, 1958 9. Z. I. KUZNETSOVA, V. S. IVANOVA and N. N. SHORYGINA, Izv. Akad. Nauk odt. khim. n., No. 9, 1886, 1963 10. M. Z. GAVRILOV and I. N. YERMOLENKO, Zh. prikl, spektroskopii 5: 762, 1966
1906
A. SH. GOIKHMAI~
11. M. Z. GAVRILOV and I. N. YERMOLENKO, Zh. prikl, spektroskopii 6: 197, 1967 12. Ch. N. R. RAO, Elektronnye spektry v khimii (Electron Spectra in Chemistry). Izd. "Mir", 1964 13. I. N. YERMOLENKO and M. Z. GAVRILOV, Reports on I Conf. on Use of Methods of Molecular Spectral Analysis (Russian), publ. by Byeloruss. State Univ., 1958 14. I. N. YERMOLENKO and M. Z. GAVRILOV, Vestnik Akad. Nauk BSSR, set. fiz.-mat. n., No. 4, 126, 1966
X-RAY
S T U D Y OF T H E O R I E N T A T I O N
DISTRIBUTION
OF C R Y S T A L L I T E S * A. SH. GOIKHMAN
Kiev Branch of the All-Union Synthetic Fibre Research Institute (Received 6 June 1966)
X-RAY scattering in a crystallite system with ideal uniaxial orientation and statistical azimuthal distribution of the crystallites (a texture with complete rotation) produces a pattern like the X-ray diagram of a rotating crystal. In this case a certain direction in the crystal, e.g. normal to hkl, makes a quite definite angle with the texture axis, and this angle is the same for all crystallites. I n a concrete case, for instance in partially oriented fibres and films, there is a certain dispersion of crystallites relative to the texture axis and the points in the X-ray diagram of the texture are blurred into arcs ("sickles") along D e b y e Sherrer rings. It is thought that the cryst~llite distribution relative to the texture axis can be estimated from the intensity distribution along these ares. Let us consider the connection between the intensity distribution for the interference of hkl with respect to the azimuthal angle J (read off the meridian in the X-ray picture of the fibre) and the distribution of the crystallites. Let us say the position of the crystallite is the direction normal to hk/--one of the many crystallographic axes. We know [1] that the integral reties intensity in an X-ray texture diagram is connected with the intensity of the same reflex in the X-ray rotation diagram of a single crystal b y the relationship
tox =Irotn/2
(1)
where Itex, trot are the integral intensities in the texture diagram and rotation diagram respectively; ~ is the number of crystallites making a contribution to "~tex °
* Vysokomol. soyed. A9: No. 8, 1693-1698, 1967.