Polymers for Fibers and Elastomers - American Chemical Society

2 Cross-Polarization/Magic Angle Spinning Study

13

C-NMR

Molecular Chain Conformations of Native and Regenerated Cellulose

Downloaded by UNIV OF OKLAHOMA on October 28, 2014 | http://pubs.acs.org Publication Date: August 29, 1984 | doi: 10.1021/bk-1984-0260.ch002

F. HORII, A. HIRAI, and R. KITAMARU Institute for Chemical Research, Kyoto University, Uji, Kyoto 611, Japan 13

Quantitative analysis of CP/MAS C NMR spectra has been carried out to characterize molecular chain conformations of crystalline and noncrystalline components of native cellulose such as cotton, ramie, bacterial, and valonia cellulose, and regenerated cellulose. The resonance lines of C1 and C4 carbons in the β-1,4glycosidic linkage and C6 carbon of the CHOH side group are deconvoluted into the crystalline and noncrystalline components. The chemical shifts of the two components of the C1, C4, and C6 carbons as determined by the line deconvolution method are correlated to the torsion angles Фand Ψabout the β-1,4-glycosidic linkage and X about the exo-cyclic C5-C6 bond, respectively. On the basis of these results, the characteristic chain conformations of the crystalline and noncrystalline components of native and regenerated cellulose are discussed. 2

Cellulose, which i s one of the most abundant organic substances found i n nature, has been extensively studied by various techniques such as x-ray s c a t t e r i n g , electron microscopy, IR and Raman spectroscopy, NMR spectroscopy e t c . However, the c r y s t a l structure and noncrystalline state are not yet solved for cotton, ramie, b a c t e r i a l and valonia c e l l u l o s e s which can be e a s i l y obtained i n Dure form. Crosspolarization/magic angle spinning(CP/MAS) NMR spectroscopy i s a promising new method to study these unsolved problems of c e l l u l o s e , because this method i s very sensitive to l o c a l molecular conformations and dynamics. Our recent CP/MAS NMR work(1,2) on native and regenerated celluloses has shown that the resonance l i n e s can be analyzed i n terms of the contribution from the c r y s t a l l i n e and noncrystalline components. The chemical s h i f t s of CI, C4, and C6 carbons thus ascribed to the respective components could be correlated to the torsion angles (> | and ip, which define the conformation about the 61,4-glycosidic linkage, and x about the exo-cyclic C5-C6 bond, 0097-6156/84/0260-0027$06.00/0 © 1984 A m e r i c a n C h e m i c a l Society

In Polymers for Fibers and Elastomers; Arthur, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

28

POLYMERS

FOR FIBERS A N D E L A S T O M E R S

respectively(_3,4) . In this paper we review these results and discuss the chain conformations of the c r y s t a l l i n e and noncrystalline components for both native and regenerated c e l l u l o s e samples.


Experimental Sample Preparation. Valonia c e l l u l o s e was obtained from the c e l l walls of valonia maorophysa. The valonia c e l l walls were p u r i f i e d as follows. They were washed with water thoroughly, boiled i n a 1% NaOH aquous solution f o r 4 hr, and washed well with water. Then they were immersed i n 0.1% acetic acid to neutralize the trace of the a l k a l i , washed with water, and dried. Aoetobaoter xyUnion, American Type Culture C o l l e c t i o n s t r a i n number 10245, which was kindly supplied by Dr. H. Takai of Hokkaido University, was grown i n a s t e r i l e l i q u i d medium. This consisted o f ( i n g / l i t e r ) : anhydrous glucose 20, yeast extract 5, polypeptons 5, disodium hydrogen phosphate(anhydrous) 2.7, and c i t r i c acid 1.15. The pH of the mixture was 7.0. 100 ml Erlenmeyer flasks f i l l e d with 15 ml of the l i q u i d medium were simultaneously inoculated with 0.5 ml of inoculum from 2-4 day inoculation culture. Cultures were grown at 30°C f o r 4 days with no a g i t a t i o n . Cellulose membranes which were produced on the surface of the l i q u i d were washed with water, immersed i n 2% NaOH solution f o r more than 7 days at room temperature, then washed again with water. To free the membranes from the a l k a l i they were immersed i n 1% acetic acid f o r 1 day, washed with water and dried. Egyptian cotton, ramie and cupra rayon f i b e r s were p u r i f i e d according to the methods reported previously(_5,j6) . A highly c r y s t a l l i n e cellulose II sample with low molecular weight was prepared using a method based on that of Bulleon and Chanzy(7). Five grams of c e l l u l o s e acetate were mixed with 150 ml dichloromethane, 100 ml acetic anhydride, 45 ml g l a c i a l acetic acid, and 0.2 ml HCIO4(density 1.67 gem" ) and maintained f o r 6 hr at 5 5 ° C The reaction was stopped by adding sodium acetate(2.5 g) suspended i n a small amount of water. The reaction mixture was then poured into 3 I of b o i l i n g 0.1 M aqueous sodium acetate. The p r e c i p i t a t e was f i l t e r e d , washed with water, then s t i r r e d i n methanol to remove oligomers of low molecular weight and the yellow color. The c e l l u l o s e triacetate(1.5g) with low molecular weight thus produced was dissolved i n 1 I of a 40% solution of methylamine i n water. The solution was held at 90°C for 5 hr to e f f e c t deacetylation and c r y s t a l l i z a t i o n of the cellulose. Other c e l l u l o s e and monosaccharides and disaccharides were the same as reported previously(1,_3) . The samples except f o r hydrates and 3-methyl cellobioside«CH30H were well dried at 50°C under vaccum for 2-3 days before and a f t e r packing i n a rotor for CP/MAS measurements. The hydrates and $-methyl cellobioside*CH3OH were used without drying. 3

1 3

1 3

CP/MAS C NMR Spectroscopy. CP/MAS C NMR spectra were recorded on a JEOL JNM FX-100 and FX-200 spectrometers equipped with a CP/MAS unit operating at 25 and 50 MHz f o r respectively. The matched f i e l d strengths V and V m of 71 kHz f o r 25 MHz and 62.5 kHz f o r 50 MHz were applied to 13c and -^-H for 2.0 ms; Vjjj remained on during the s i g n a l a c q u i s i t i o n period. Magic angle spinning was c a r r i e d out l c


2.

HORII E T A L .

CP/MAS C-NMR

29

Study

13

at a rate of about 3.2 kHz for 25 MHz and 3.5 kHz f o r 50 MHz by use of a b u l l e t type rotor of poly(chlorotrifluoroethylene), whose volume was about 0.5 cm . Chemical s h i f t s r e l a t i v e to tetramethylsilane( TMS) were determined using a narrow c r y s t a l l i n e resonance l i n e at 33.6 ppm for polyethylene inserted i n a l l samples. 3

Results and Discussion


1. Assignments of the Resonance Lines of the C r y s t a l l i n e and Nonc r y s t a l l i n e Components. Figure 1 shows a 50 MHz CP/MAS NMR spectrum of ramie c e l l u l o s e and a stick-type NMR spectrum of low molecular weight c e l l u l o s e ( DP'VLO) i n deuterated dimethyl sulfoxide solution(DMSO)(8)(The broken and s o l i d l i n e s i n the CP/MAS spectrum w i l l be explained below.). As already reported(9,10), the assignments f o r the CI, C4 and C6 carbons are r e l a t i v e l y easy, based on analogies with the solution state spectrum. However, i t should be noted that these resonance l i n e s s h i f t downfield by 2.3-9.6 ppm i n the s o l i d state compared to the solution state. The cause of such large downfield s h i f t s ( t o be explained i n the next section) i s attributed to the d i f f e r e n t conformations about the $-l,4-glycosidic linkage and the exo-cyclic C5C6 bond i n which these carbons are involved. Another remarkable feature i s that the resonance l i n e s of the C4 and C6 carbons s p l i t into two components; sharp downfield and broad u p f i e l d components. Similar s p l i t t i n g s have been observed f o r the C4 and C6 resonance lines of cotton, b a c t e r i a l and valonia c e l l u l o s e and for the CI, C4 and C6 resonance l i n e s of regenerated cellulose(1) such as cupra rayon f i b e r s . These spectra and s p l i t t i n g s are shown i n Figure 2. In the case of regenerated c e l l u l o s e ( 1 ) , we have already concluded that the components causing the sharp downfield and the broad u p f i e l d s h i f t s are the c r y s t a l l i n e and noncrystalline components, respectively. Therefore, we have assumed that the s p l i t tings are due to the same components i n native c e l l u l o s e . However, the CI resonance l i n e does not seem e x p l i c i t l y to contain two such components. In order to confirm this assumption, we deconvoluted the C4 and C6 resonance l i n e s into two components by use of a curve resolver and by assuming a Lorentzian l i n e shape as shown by broken and thin s o l i d l i n e s i n Figures 1 and 2. In Figure 3 the integrated f r a c t i o n / of the sharp downfield component of the C4 carbon i s plotted against the degree of c r y s t a l l i n i t y / determined by x-ray analysis based on a modified Hermans' method(l,ll,12). This figure shows also data of hydrocellulose, some regenerated c e l l u l o s e samples(l), and mercerized cotton and ramie. A l i n e a r relationship exists between / and / for a l l the samples. A s i m i l a r relationship was also obtained f o r the case of the C6 resonance l i n e . Therefore, i t i s concluded that the sharp downfield and broad u p f i e l d components of the C4 and C6 carbons of native c e l l u l o s e are also the c r y s t a l l i n e and nonc r y s t a l l i n e components, respectively.*) Recent work(13) reported that the broad u p f i e l d components of C4 and C6 carbons were not attributed to the noncrystalline component but to anhydroglucoses on the surface of elementary f i b r i l s because the spectra of cotton, hydrocellulose, and ramie showed l i t t l e differences i n r e l a t i v e i n t e n s i t y and i n appearance of the broad n

m

x

n

m


r

x

r

30

P O L Y M E R S FOR F I B E R S A N D

ELASTOMERS


6

J - I • I . I i I . I . I , 120 110 1 0 0 9 0 80 70 60 ppm

Figure 1. 50MHz CP /MAS C NMR spectrum of ramie and stick-type scalar-decoupled l ^ C NMR spectrum of low molecular weight c e l l u l o s e i n DMSO-dg solution (8). Broken and t h i n s o l i d l i n e s i n the CP/MAS spectrum are for the c r y s t a l l i n e and noncrystalline components, respectively. 1

110

100

3

90 ' 80 ' 70 ' 60 ' ppm

110

1 0 0 ' 90

80

70 60 ppm

1 3

Figure 2. 50 MHz CP/MAS C NMR spectra of b a c t e r i a l c e l l u l o s e , valonia c e l l u l o s e , cotton, and cupra rayon f i b e r s . Broken and t h i n s o l i d l i n e s i n the CP/MAS spectra are for the c r y s t a l l i n e and nonc r y s t a l l i n e components, respectively.


HORII ET AL.


2.

CP/MAS

C-NMR

13

Study

31

component. However, i t i s very plausible that such differences could not be found among these samples, because their c r y s t a l l i n i t i e s are almost the same. More importantly, they believed that the c r y s t a l l i n i t i e s of these samples were 80-96%. We think that these values are evidently overestimated. According to our quantitative analysis described above i t i s not necessary to consider the contribution of the surface of elementary f i b r i l s to the broad components. On the other hand, the resonance l i n e of the CI carbon i s also assumed to contain c r y s t a l l i n e and noncrystalline components. In order to examine this problem, we measured s p i n - l a t t i c e relaxation times using a pulse sequence as developed by Torchia(16). As a r e s u l t , i t has been found that each resonance l i n e of ramie contains two components with values of 4.6-16s and 65-130s which correspond to the noncrystalline and c r y s t a l l i n e components, respectively(15). On the basis of these d i f f e r e n t values, we were able to record the spectra of the c r y s t a l l i n e and noncrystalline components of native cellulose separately by appropriate pulse techniques. Figure 4(A) shows the spectrum of the c r y s t a l l i n e component of ramie which was obtained under the MAS condition by a pulse sequence for measurements developed by Torchia(16) . The time between the two TT/2 pulses was about 30s. As i s c l e a r l y seen, the broad u p f i e l d components of the C4 and C6 resonance l i n e s disappear and another fine s p l i t t i n g appears i n the CI resonance l i n e which originates only from the c r y s t a l l i n e component. Figure 4(B) shows the spectrum of the noncrystalline component of ramie which was obtained by a conventional TT/2 single pulse sequence with a short waiting time of 4s employing the DD/MAS technique. As the difference i n T-^ between the c r y s t a l l i n e and noncrystalline components i s not very large, a small amount of the downfield c r y s t a l l i n e l i n e s also appears for the C4 and C6 carbons. Although a small amount of the c r y s t a l l i n e component i s also involved i n the CI resonance l i n e , the characteristics of the noncrystalline component of this l i n e can be well observed: the chemical s h i f t of this component i s about 106 ppm from TMS and the l i n e width i s about 90 Hz. By considering the features of the CI resonance l i n e for both components, we deconvoluted the CI resonance l i n e into the c r y s t a l l i n e and noncrystalline components as shown i n Figure 1. Although two Lorentzian l i n e s were used for the c r y s t a l l i n e components based on the r e s u l t i n Figure 4 (A), the CI l i n e could be deconvoluted into the two components. The integrated f r a c t i o n of the c r y s t a l l i n e component was also i n good accord with the f^?Similar deconvolutions were also possible for the CI resonance l i n e s of cotton, b a c t e r i a l and valonia c e l l u l o s e s as shown i n Figure 2. I t shoud be noted that three Lorentzian l i n e s were used for the c r y s t a l l i n e component of the l a t t e r two samples.

*) Garroway et al.(14) have recently pointed out that the r e l a t i v e i n t e n s i t i e s of resonance l i n e s of CP/MAS -^C NMR spectra are proport i o n a l to the number of carbons, when the time constant T q for -4113 cross p o l a r i z a t i o n i s much shorter than the s p i n - l a t t i c e relaxation times T]Jp and T ^ p i n the rotation frames of ^-H and -^C n u c l e i , respectively. Since this condition has been found to be f u l f i l l e d under our experimental condition(15), such a quantitative analysis as shown i n the text can be reasonably carried out for c e l l u l o s e samples. H

C


32

POLYMERS

F O R FIBERS

A N D

ELASTOMERS


1.0

Ol 0

i

0.5

I 1.0

fx

Figure 3

Integrated f r a c t i o n /

of the downfield component of the nmr

C4 resonance l i n e v s . degree of c r y s t a l l i n i t y / analysis.

determined by x-ray

•: native c e l l u l o s e , o: regenerated c e l l u l o s e ,

Q: mercerized cotton and ramie.

(The data of regenerated c e l l u l o s e

samples except f o r cupra rayon fibers were reproduced from Ref. 1.)

120 ' 110 ' 1 0 0 ' 9 0 " 8 0 ' 7 0 ' 6 0 ppm

Figure 4

P a r t i a l l y relaxed 2 5 MHz

C NMR spectra of the c r y s t a l -

l i n e and noncrystalline components of ramie which were separately measured by a pulse sequence f o r CP T^ measurements developed by Torchia(16) and a single TT/2 pulse sequence, respectively.



2.

HORII E T A L .

CP/MAS

C-NMR

13

Study

33

The pulse techniques employed for the s e l e c t i v e observation of the c r y s t a l l i n e and noncrystalline components f o r native c e l l u l o s e are also useful for regenerated c e l l u l o s e . Figure 5 shows the spectrum of the c r y s t a l l i n e component of cupra rayon f i b e r s together with that of a regenerated c e l l u l o s e sample(JL) of high c r y s t a l l i n i t y . The good agreement of the two spectra confirms that very sharp l i n e s of the c r y s t a l l i n e component are involved i n the respective l i n e s of the whole spectrum of the rayon f i b e r s which i s r e l a t i v e l y broad as shown i n Figure 2. The chemical s h i f t s of CI, C4, and C6 carbons of the c r y s t a l l i n e and noncrystalline components of native and regenerated c e l l u l o s e s are tabulated i n Tables I and I I , respectively. Table I I shows also the l i n e width Av of each resonance l i n e . Before we discuss these r e s u l t s , l e t us consider the meanings of the s o l i d - s t a t e -^C chemical s h i f t s i n the next section. 2. Relationships between -^C Chemical Shifts and the Corresponding Torsion Angles. 1 3

The C i s o t r o p i c chemical s h i f t s obtained by CP/MAS technique are also determined by the magnetic shielding of electrons surrounding concerned carbons just as i n s o l u t i o n . Nevertheless, MAS can produce high-resolution l i n e s without any a i d of molecular motions. Therefore, the respective states of electron shielding fixed i n the s o l i d state are r e f l e c t e d on the respective chemical s h i f t s of a given carbon, whereas such states are usually averaged out i n solution by rapid inner molecular motions. This suggests that the s o l i d - s t a t e chemical s h i f t s provide important information of the l o c a l conformations and alignments of molecules i n the s o l i d state which possibly determine the extent of the electron s h i e l d i n g . However, the s o l i d - s t a t e chemical s h i f t s are not well understood at present. The main e f f e c t s which have been pointed out hitherto are the e f f e c t s of packing, hydrogen bonding, and torsion angles about chemical bonds involving concerned carbons. In r e l a t i o n to the packing e f f e c t , VanderHart(17) has found that the resonance l i n e of CH2 carbons of t r i c l i n i c c r y s t a l s of W-C20H42 i s shifted 1.31"0.4 ppm downfield i n comparison to that of n-paraffins of other c r y s t a l forms. As for the hydrogen bonding e f f e c t s , Terao et al.(18-20) have reported that large downfield s h i f t s appear for the carbons bonded chemic a l l y to hydroxyl groups which form strong hydrogen bonds. F i r s t we have examined these two e f f e c t s for the c r y s t a l s of monosaccharides and disaccharides which are compounds related to c e l l u l o s e . Table I I I compares the C CP/MAS chemical s h i f t s i n the s o l i d state and the corresponding s h i f t s i n D2O. The comparison i s made only for carbons not associated with exo-cyclic C-C bonds and $-1,4glycosidic linkages. The respective resonance l i n e s of the s o l i d state spectra of a-glucose and $-glucose and of the solution spectra of a l l the samples were assigned according to the results of Pfeffer et al.(21,22) In the table are also shown the 0«»»0 distances of the hydrogen bonds i n the s o l i d state(23-26). The difference A6 i n chemical s h i f t between the two states ranges from -1.51 ppm to 2.43 ppm and are independent on the 0»««0 distances. Therefore, the hydrogen bonding seems not to s i g n i f i c a n t l y a f f e c t the chemical s h i f t s i n these carbohydrates. However, the somewhat large 1 3



34

POLYMERS

FOR FIBERS A N D

ELASTOMERS

120" 110 ' 100" 90 ' 80 ' 70 ' 60 ' ppm

Figure 5

50 MHz

1 3

CP/MAS C

NMR

spectrum

(A) of highly c r y s t a l l i n e 13

c e l l u l o s e II sample and p a r t i a l l y relaxed 25 MHz

C NMR

spectrum

(B) of the c r y s t a l l i n e component of cupra rayon f i b e r s which was separately measured by the pulse sequence for CP T

measurements.

Table I 'C Chemical Shifts of the C r y s t a l l i n e Components of Native and Regenerated Cellulose

chemical shift/ppm C6

C4

CI

sample native c e l l u l o s e valonia

107.0

106.4

105.3

91.3

90.1

66.5

105.3

91.0

90.1

66.4

bacterial

107.3

cotton

107.1

105.4

89.9

66.5

ramie

107.2

105.0

89.7

66.0

cupra rayon

108.0

106.3

89.5

88.2

64.1

high-crystalline cellulose II

108.1

106.3

89.6

88.4

63.7

106.3

regenerated c e l l u l o s e


2.

HORII E T A L .

CP/MAS

"C-NMR

Study

35

Table I I 13

C

Chemical Shifts and Line-Widths of the Noncrystalline Components of Native and Regenerated Cellulose

CI

C4

C6

6/ppm

Av/Hz

6/ppm

Av/Hz

6/ppm

Av/Hz

valonia

106.2

114

85.2

249

63.4

185

bacterial

106.6

120

85.0

242

63.4

163

cotton

106.0

143

85.1

256

63.7

185

ramie

105.8

128

84.8

284

63.0

171

cupra rayon

105.3

284

85.1

327

62.8

185

amorphous

105.2

284

81.6

284

62.8

284

sample


native c e l l u l o s e

regenerated c e l l u l o s e

Table I I I 13 Comparison of C Chemical S h i f t s of Monosaccharides and Disaccharides i n the S o l i d State and i n Solution

6/ppm Sample

Carbon

A6/ppm Solid

a-D-glucose

0•••0 distance/A

solution

1 2 3 4

93.54 71.22 73.75 73.36

93.30 72.73 74.05 70.93

0.24 -1.51 -0.30 2.43

2.847 2.776 2.707 2.773

1 2 3 4

97.34 76.39 76.39 70.34

97.15 75.46 77.17 70.93

0.19 0.93 -0.78 -0.59

2.666 2.686, 2, 2.772 no

$-D-cellobiose

1'

98.02

97.05

0.97

2.776

b

Ot-D—lactose monohydrate

1'

93.50

93.15

0.35

2.790

c

$-D-lactose

1'

99.00

97.10

1.90

2.772

d

$-D-glucose

a.

Ref. 23 b. Ref. 24

c. Ref. 25

a

a

a

a

b

b

b

d. Ref. 26



36

POLYMERS

FOR FIBERS A N D

ELASTOMERS

difference A6 may originate from t o t a l intermolecular effects such as packing and hydrogen bonding e f f e c t s . In Table IV the s o l i d - s t a t e chemical s h i f t s of the carbons of ramie which are involved i n the 3-1,4-glycosidic linkages and i n the exo-cyclic C-C bonds are compared with the corresponding values of low molecular weight c e l l u l o s e i n DMSO solution(8). In this case the A6 values are as large as 2.3-9.8 ppm, suggesting that such larger differences may stem from the difference i n the torsion angles , determined from x-ray analyses(24-28) , for d i f f e r ent disaccharides of the $-l,4-glycosidic linkages(4). The chemical s h i f t s of the c r y s t a l l i n e components of d i f f e r e n t c e l l u l o s e samples which are shown i n Table I are also plotted against the corresponding ((> values (29-32) . In the l a t t e r case two or three d i f f e r e n t s h i f t values are plotted against the same (j) values except f o r the case of ramie where two d i f f e r e n t (j) values have been determined by x-ray analysis(31) . Although the data are somewhat scattered., the chemical s h i f t of CI carbon seems to be correlated to the torsion angle ((). Figure 7 shows the similar plot of the chemical s h i f t s of C4 carbon against the torsion angles \p determined by x-ray analyses. As a l i n e a r relationship also exists between them, the chemical s h i f t of the C4 carbon seems to be dependent on the torsion angles ip. In Figure 8, the C chemical s h i f t s of C6 carbon are plotted against the torsion angles x about C5-C6 bonds for glucose and glucose residues of d i f f e r e n t disaccharides and c e l l u l o s e ( 3 ) . In this case there exists also a l i n e a r relationship between the two parameters. According to a recent survey(33) of the rotations about the C-C bonds i n low molecular weight glucosides, gauche-gauche and gauche-trans are the two favored conformers. In agreement with t h i s f a c t , no data of monosaccharides and disaccharides are included i n this figure which correspond to the x values around 300°. On the other hand, the conformation of the CH2OH groups of the c r y s t a l l i n e component of native c e l l u l o s e i s found to be trans-gauche(29,31) against the expectation from the data of low molecular weight glucosides. Figure 8 shows that these three preferred conformations are well correlated to the chemical s h i f t s of "the C6 carbon; gauchegauche, gauche-trans, and trans-gauche correspond to the chemical s h i f t s of about 62 ppm, 62.7-64.5 ppm, and about 66 ppm,respectively. It i s concluded that the s o l i d - s t a t e chemical s h i f t s of the CI, C4, and C6 carbons are mainly correlated to the torsion angles (j>, i[>, and x> respectively. However, the intermolecular e f f e c t s such as packing and hydrogen bonding produce t o t a l l y the downfield or u p f i e l d s h i f t of 0.2-2.4 ppm f o r the carbohydrates studied here. Therefore, when the downfield or u p f i e l d s h i f t of such an order appears even i n the s o l i d - s t a t e l^C NMR spectra, the intermolecular e f f e c t s must be also considered. 1 3

3. Chain Conformation of the C r y s t a l l i n e and Noncrystalline Components of Cellulose. F i r s t we discuss the chemical s h i f t s of the c r y s t a l l i n e components shown i n Table I. The CI and C4 resonance l i n e s of valonia and


2.

HORII E T A L .

CP/MAS

"C-NMR

Study

37

Table IV Comparison of Chemical Shifts of CI, C4 and C6 Carbons of Ramie i n the Solid State with Those of Low Molecular Weight Cellulose i n Solution

6/ppm

A6/ppm

Carbon Crystalline


J

1

107.2, 105.0

4 6 a.

®on,. Solution crystalline

a

Crystalline J

102.7

89.9

84.8

80.1

9.8

4.7

66.0

63.0

60.6

5.4

2.4

20

2.3

n

105.8

i n deuterated dimethyl

4.5,

n

^° -. crystalline 3.1

sulfoxide(8).

40

60

80

^/degree 13 Figure 6 .

C chemical s h i f t s of the CI carbons vs. torsion angles

a: $-D-cellobiose, b: $-D-methyl cellobioside'CH^OH, c:

a-D-

lactose monohydrate, d: 3-D-lactose, e: c e l l u l o s e I (29), f: c e l l u l o s e I (31), g: c e l l u l o s e II (30), h: c e l l u l o s e II (32). (Data a-d, g-h; Ref.

4.)



38

POLYMERS

F O R FIBERS A N D

ELASTOMERS

t|V degree Figure 7 . chemical s h i f t s of the C4 carbons v s . torsion angles a: /3-D-cellobiose, b: 0-D-methyl cellobioside-CI^OH, c: Qf-Dlactose monohydrate, d: j3-D-lactose, e: c e l l u l o s e I ( 2 9 ) , f : c e l l u l o s e I ( 3 1 ) , g: c e l l u l o s e I I ( 3 0 ) , h: c e l l u l o s e II ( 3 2 ) . (Data a-e, g-h; Ref. 4 . ) 68

1

i

i

i

i

g

••

66-

*

E

c /

CL CL

-

•

if) o 62

-

e

E

Polymers for Fibers and Elastomers - American Chemical Society

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