The Structures of Cellulose - American Chemical Society

Chapter 10

Solid-State Carbon-13 NMR and Wide-Angle X-ray Scattering Study of Cellulose Disordering by Alkali Treatment B. Philipp, J. Kunze, and H.-P. Fink Academy of Sciences of the German Democratic Republic, Institute of Polymer Chemistry "Erich Correns," 1530 Teltow-Seehof, German Democratic Republic

13

High resolution solid state C NMR spectroscopy supplemented by WAXS measurements proved to be a useful tool in elucidating struc tural changes of cellulose due to chemical transformations and phase transitions (1). TheC-CP/MAS-NMR spectra are sensitive to changes in chain conformation and packing density as well as to spe c i f i c changes in the chemical environment of the different OH-groups of the anhydroglucose units. In our previous work in this field we discussed C solid state NMR spectra of alkali cellulose and its dependence on NaOH concentration, experimentally obtained by us for the first time (2). Furthermore, we discussed the spectra of various samples of regenerated cellulose differing in supermolecular order (3). Quite recently, Kamide (4,5) in a more detailed C NMR study on cellulose and i t s alkalization process correlated the changes in the C NMR spectrum to a selective weakening or even destruction of the Η-bonds in the cellulose moiety. The following contribution summarizes some C NMR and WAXS results of a s t i l l preliminary kind comparing the "disordering effects" obtained by aqueous and ethanolic NaOH solutions, and by aqueous guanidonium hydroxide to that achieved by ball-milling of cellulose samples. 13

13

13

13

13

Experimental As s t a r t i n g m a t e r i a l s we m a i n l y used an a c e t a t e grade s c o u r e d and b l e a c h e d c o t t o n l i n t e r s (DP i n cuprammonium s o l u t i o n ~ 1500) and a c e l l u l o s e powder p r e p a r e d from l i n t e r s by h y d r o l y s i s t o DP ~ 150 and a subsequent m e c h a n i c a l d i s i n t e g r a t i o n . In t h e experiments w i t h guanidonium h y d r o x i d e t h e s e samples were a l s o employed a f t e r p r e v i o u s m e r c e r i z a t i o n w i t h 18% by weight aqueous NaOH. F o r comparison a l s o l i n t e r s and v i s c o s e s t a p l e f i b r e b e f o r e and a f t e r b a l l - m i l l i n g as w e l l as a l i n t e r s sample d e c r y s t a l l i z e d by N2O4-treatment a c c o r d i n g t o (6) were i n c l u d e d i n o u r work. A l k a l i n e treatment was performed w i t h an e x c e s s o f s t e e p i n g l y e a t room temperature, employing aqueous as w e l l as e t h a n o l i c ( e t h a n o l : w a t e r = 70:30% by w e i g h t ) s o l u t i o n s o f NaOH up t o 30% by weight. Treatment w i t h guanidonium h y d r o x i d e was a c c o m p l i s h e d i n

0097-6156/87/0340-0178$06.00/0 © 1987 American Chemical Society

10.

Cellulose Disordering by Alkali Treatment

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179

a l l e x p e r i m e n t s w i t h an aqueous s o l u t i o n o f about 50% by weight. A f t e r f i l t e r i n g o f f the e x c e s s o f l y e , samples were n e u t r a l i z e d w i t h aqueous o r e t h a n o l i c a c e t i c a c i d , washed w i t h water o r e t h a n o l and d r i e d at 25°C. In some s e r i e s the l y e was washed out w i t h water o r ethanol without a d d i t i o n of a c e t i c a c i d . The p r o c e d u r e a p p l i e d i n each s e r i e s i s i n d i c a t e d i n the t a b l e s or i n the c a p t i o n s t o figures. The C-CP/MAS-NMR-spectra o f the NaOH-treated and o f a l l the r e g e n e r a t e d samples were r e g i s t e r e d a t room temperature w i t h a homeb u i l t s p e c t r o m e t e r a t 15.087 MHz and w i t h a f i e l d o f 1.5 mT f o r d i p o l a r d e c o u p l i n g (_7_) · Frequency f o r sample r o t a t i o n was about 2 kHz, the r e p e a t time 2 s ( w i t h b a c k f l i p p u l s e ) and the d u r a t i o n o f c r o s s - p o l a r i z a t i o n 1.5 ms. The assignment o f the s i g n a l s to the d i f f e r e n t C-atoms o f the a n h y d r o g l u c o s e u n i t was based on e x p e r i e n c e o f our own and on r e l e v a n t d a t a p u b l i s h e d i n (SO. The MAS technique proved t o be a p p l i c a b l e t o the r a t h e r h i g h l y s w o l l e n samples o f Nac e l l u l o s e without s e r i o u s problems (2_), w h i l e the g e l - l i k e s t r u c t u r e o f guanidonium c e l l u l o s e c o u l d not be i n v e s t i g a t e d employing t h i s method. With r e g a r d t o the i n f l u e n c e o f CP-impulse l e n g t h we r e l i e d on the r a t h e r numerous and r e l i a b l e d a t a a l r e a d y p u b l i s h e d [comp. (18)] i n d i c a t i n g t h a t no s i g n i f i c a n t d i f f e r e n c e s between r e g i o n s o f d i f f e r e n t p h y s i c a l s t r u c t u r e a r e t o be expected. G e n e r a l l y the s p e c t r a were t a k e n w i t h about 5000 scans. With s e v e r a l samples a l k a l i z e d i n the e t h a n o l system o n l y 2000 scans c o u l d be performed r e s u l t i n g i n a lower s i g n a l t o n o i s e r a t i o s t i l l s u f f i c i e n t f o r d e r i v i n g r e l i a b l y the i n f o r m a t i o n s u b s e q u e n t l y d i s c u s s e d . WAXS p a t t e r n s o f the a l k a l i z e d and the r e g e n e r a t e d samples were o b t a i n e d by the t e c h n i q u e d e s c r i b e d i n (9_) · E v a l u a t i o n was p e r formed w i t h r e g a r d to l a t t i c e type, i n some c a s e s a l s o w i t h r e g a r d t o degree o f c r y s t a l l i n i t y and average l a t e r a l c r y s t a l d i m e n s i o n s 13

(10). Results 3

In F i g u r e 1 the ^ C s p e c t r a o f l i n t e r s and v i s c o s e s t a p l e f i b r e a r e shown i n the o r i g i n a l s t a t e , a f t e r d e c r y s t a l l i z a t i o n by b a l l - m i l l i n g , and a f t e r s u b s e q u e n t l y b o i l i n g the m i l l e d samples i n water. S i g n i f i c a n t changes i n the spectrum due t o d e c r y s t a l l i z a t i o n a r e v i s i b l e mainly i n the C - l and C-6 r e g i o n s a t ~ 105 ppm and 60 ppm, r e s p e c t i v e l y , and i n the C-4 r e g i o n at ~ 85 ppm. In the f i r s t two r e g i o n s mentioned a s i g n a l b r o a d e n i n g o c c u r s , w h i l e a t 85 ppm l i n e s p r e s e n t i n the spectrum o f the o r i g i n a l sample d i s a p p e a r o r are smeared out to a broad s i g n a l o f low amplitude a f t e r m i l l i n g . By b o i l i n g the d e c r y s t a l l i z e d samples i n water, these changes i n the l^C spectrum a r e o n l y p a r t i a l l y r e v e r s e d . These r e s u l t s are g e n e r a l l y c o n f i r m e d by our e x p e r i m e n t s e m p l o y i n g v i s c o s e s t a p l e f i b r e ( F i g u r e l b ) . As a l s o i n d i c a t e d i n F i g u r e lb the spectrum o f the N2O4 p r e t r e a t e d s t a p l e f i b r e resembles c l o s e l y t h a t d e c r y s t a l l i z e d by b a l l - m i l l i n g . In a v i s u a l e v a u l a t i o n o f the WAXS p a t t e r n s no i n d i c a t i o n o f p e r s i s t i n g c r y s t a l l i n e peaks c o u l d be r e c o g n i z e d a f t e r our b a l l - m i l l i n g p r o c e d u r e ( 1 3 ) . F i g u r e 2 g i v e s a c o m p a r i s o n o f the NMR s p e c t r a o f a l k a l i - t r e a t e d samples a f t e r s t e e p i n g w i t h aqueous NaOH ( S p e c t r a 2a) (2_), o r e t h a n o l i c NaOH ( e t h a n o l : w a t e r = 70:30% by w e i g h t ) ( S p e c t r a 2b) p r i o r

180

THE STRUCTURES OF CELLULOSE

76

A

Β

Figure l a .

13

CP/MAS- C-NMR-spectra o f c o t t o n l i n t e r s a f t e r v a r i o u s t r e a t m e n t s ( c h e m i c a l s h i f t s i n ppm r e l a t i v e t o TMS = 0 ) . A - ball milled Β - b a l l m i l l e d and b o i l e d i n water C - o r i g i n a l s t a t e ( o r i g i n a l sample w i t h o u t f o r comparison)

Figure lb.

CP/MAS-13c-NMR-spectra o f v i s c o s e various treatments.

staple

treatment

fibre after

A - ball milled Β - b a l l m i l l e d and b o i l e d i n water C - o r i g i n a l s t a t e ( o r i g i n a l sample w i t h o u t f o r comparison) D - t r e a t e d w i t h N2O4

treatment

10.

PHILIPP ET AL.

Figure

2b.


13

CP/MAS- C-NMR-spectra o f h y d r o l y z e d c o t t o n l i n t e r s powder a f t e r t r e a t m e n t w i t h e t h a n o l i c NaOH.

182


to regneration. As a g e n e r a l tendency, a b r o a d e n i n g and f l a t t e n i n g out o f a l l t h e l i n e s as w e l l as a s h i f t i n g o f t h e s i g n a l s ( T a b l e I ) can be o b s e r v e d a t a s u f f i c i e n t l y h i g h l y e c o n c e n t r a t i o n . Also a s i g n i f i c a n t i n f l u e n c e o f t h e r e a c t i o n medium becomes c l e a r l y v i s i b l e from these s p e c t r a : The l i n e - s h i f t i n g and t h e b r o a d e n i n g o f t h e C - l , C-4 and C-6 l i n e s b e g i n a t a much lower NaOH c o n c e n t r a t i o n w i t h the N a O H - s o l u t i o n i n e t h a n o l as compared t o t h e aqueous system. The spectrum r e c o r d e d a f t e r s t e e p i n g w i t h 12% by weight e t h a n o l i c l y e i s v e r y s i m i l a r t o t h a t o b t a i n e d a f t e r a c t i o n o f a 24% by weight aqueous l y e .

Table

I.

L i n e P o s i t i o n s o f C e l l u l o s e A f t e r A l k a l i Treatment (ppm r e l a t i v e t o TMS = 0)

Aqueous medium 9% 12% 15%

NaOH by weight

105 106 106

88 89/86 85

75/72 75/72 76/74

66 66/60 62

90

77/74 77 77

67 (66)

E t h a n o l i c medium 4% 8% 12%

NaOH by weight

107 106 104

— —

—

At lower N a O H - c o n c e n t r a t i o n t h e l i n e s h i f t i n g i n t h e C - l , C-4 and t h e C-6 r e g i o n due t o i n t e r a c t i o n w i t h NaOH a r e d i f f e r e n t and even o p p o s i t e i n d i r e c t i o n a f t e r t r e a t m e n t w i t h aqueous and w i t h ethanolic lye, respectively. W i t h r e s p e c t t o changes i n t h e WAXS p a t t e r n i t c a n be c o n c l u d e d from o u r p r e v i o u s work (11) t h a t i n an aqueous system t h e c e l l u l o s e I p a t t e r n o f l i n t e r s c e l l u l o s e i s p e r s i s t i n g up t o 10% NaOH i n t h e l y e , and l a t t i c e t r a n s f o r m a t i o n t o N a - c e l l u l o s e i s completed a t about 15% NaOH i n t h e s t e e p i n g l y e , w i t h a r a t h e r h i g h degree o f c r y s t a l l i n e order p r e v a i l i n g d u r i n g the t r a n s i t i o n . In t h e e t h a n o l i c system, on t h e o t h e r hand, t h e c e l l u l o s e I d i f f r a c t i o n p a t t e r n c o u l d be d e t e c t e d i n t h e c o n c e n t r a t i o n range up t o 8% NaOH o n l y (comp. T a b l e I I ) , and even a t a s t e e p i n g l y e c o n c e n t r a t i o n i n t h e range between 4 and 8% NaOH a d e c r e a s e o f o r d e r was i n d i c a t e d i n t h e X-ray d i f f r a c t o g r a m . At s t i l l h i g h e r a l k a l i c o n c e n t r a t i o n t h e d i f f r a c t o g r a m m o s t l y r e v e a l e d a poor s t a t e o f o r d e r , some samples showing a f a i n t p a t t e r n o f a l k a l i c e l l u l o s e . The l ^ C NMR-spectra o f l i n t e r s c e l l u l o s e r e g e n e r a t e d a f t e r t r e a t m e n t w i t h e t h a n o l i c s o l u t i o n s o f NaOH a r e r e p r o d u c e d i n F i g u r e 3 and compared t o t h a t o f a sample s t e e p e d w i t h 12% aqueous NaOH and subsequently regenerated. The c o r r e s p o n d i n g s p e c t r a o f samples t r e a t e d w i t h 12% e t h a n o l i c and w i t h aqueous NaOH show l a r g e d i f f e r e n c e s , e s p e c i a l l y i n t h e C-4 r e g i o n . Even a NaOH c o n c e n t r a t i o n as low as 2% i n t h e e t h a n o l i c system l e a d s t o s i g n i f i c a n t d i f f e r ences between t h e l i n e p o s i t i o n s o f t h e o r i g i n a l , t h e a l k a l i - t r e a t e d

10.

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Figure

3.


183

13

CP/MAS- C-NMR-spectra o f h y d r o l y z e d c o t t o n l i n t e r s powder a f t e r a l k a l i treatment and n e u t r a l i z a t i o n , resp., regeneration to c e l l u l o s e . 4, 8, and 12% - t r e a t m e n t w i t h e t h a n o l i c s o l u t i o n o f NaOH 12% aqu. - t r e a t m e n t w i t h aqueous s o l u t i o n o f NaOH f o r comparison

184


and t h e r e g e n e r a t e d sample, p o i n t i n g t o a s t r u c t u r a l changes, a l t h o u g h the WAXS p a t t e r n i n a l l t h r e e c a s e s c l e a r l y i n d i c a t e d a c e l l u l o s e I l a t t i c e without a s i g n i f i c a n t d i f f e r e n c e i n supermolecular order. Samples r e g e n e r a t e d a f t e r t r e a t m e n t w i t h e t h a n o l i c NaOH s o l u t i o n s o f h i g h e r c o n c e n t r a t i o n c o n s i s t e d o f a more o r l e s s w e l l o r d e r e d c e l l u l o s e I I , t h e q u a l i t a t i v e e v a l u a t i o n o f the WAXS p a t t e r n s b e i n g summarized i n T a b l e I I . Comparing the C NMR s p e c t r a o f t h e two r e g e n e r a t e d samples p r e v i o u s l y t r e a t e d w i t h 16% e t h a n o l i c and 18% aqueous NaOH, r e s p e c t i v e l y , we f i n d t h e g e n e r a l f e a t u r e s o f t h e c e l l u l o s e I I spectrum i n b o t h c a s e s w i t h m i n o r d i f f e r e n c e s i n the C-4 and C-2, 3, 5 r e g i o n . 1 3

Table

II.

NaOH-Conc. by Weight

Summary o f WAXS-Results on C e l l u l o s e w i t h a NaOH/Ethanol/Water System Alkalized Samples, wet s t a t e

Samples R e g e n e r a t e d with Ethanol, d r y state

Samples T r e a t e d

Samples R e g e n e r a t e d w i t h water, d r y state

2

Cell.

I

Cell.

I

Cell.

I

4

Cell. I

Cell.

I

Cell.

I

8

Low o r d e r , two b r o a d interferences


Cell. II

12


Liquid like low o r d e r

Cell. II

16

Low o r d e r , two broad interferences


Cell. II

Our r e s u l t s o b t a i n e d on s t r u c t u r a l changes o f h y d r o l y z e d c o t t o n l i n t e r s powder by t r e a t m e n t w i t h aqueous guanidonium h y d r o x i d e a r e r e p o r t e d i n d e t a i l i n (12) and t h e r e f o r e s h a l l be o n l y b r i e f l y summarized here. The WAXS p a t t e r n s o f a l l t h e a l k a l y z e d and t h e r e g e n e r a t e d samples c l o s e l y resemble the d i f f r a c t o g r a m o f an amorphous c e l l u l o s e by v i s u a l i n s p e c t i o n , a l t h o u g h a r a d i a l e l e c t r o n d e n s i t y d i s t r i b u t i o n d e r i v e d from X-ray s c a t t e r i n g a c c o r d i n g t o (13) s t i l l r e v e a l s some r e s i d u a l s u p e r m o l e c u l a r o r d e r . The C NMR s p e c t r a o f t h e guanidonium h y d r o x i d e t r e a t e d w i t h s u b s e q u e n t l y r e g e n e r a t e d samples a r e d i f f e r e n t from t h o s e o f t h e s t a r t i n g m a t e r i a l p r e d o m i n a n t l y i n t h e C - l , C-4, and C-6 r e g i o n , e s p e c i a l l y w i t h r e g a r d t o t h e narrow p a r t i n the C-4 r e g i o n a t 88 ppm ( F i g u r e 4 ) . The i n t e n s i t y o f t h i s narrow l i n e n e a r l y d i s a p p e a r s a f t e r guanidonium h y d r o x i d e t r e a t m e n t , b u t i s r e c o v e r e d a f t e r r e c r y s t a l l i z a t i o n by b o i l i n g o f t h e r e g e n e r a t e d sample i n water. S t r u c t u a l d i f f e r e n c e s between t h e o r i g i n a l and t h e m e r c e r i z e d 1 3

10.

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l i n t e r s c e l l u l o s e powder a r e o b v i o u s l y p e r s i s t i n g d u r i n g t h e g u a n i donium h y d r o x i d e treatment and t h e subsequent p r o c e d u r e o f r e g n e r a t i o n , a s t o be seen from i n t e n s i t y and l i n e w i d t h o f t h e d i f f e r e n t samples i n t h e C - 4 r e g i o n (comp. F i g u r e 4a w i t h 4 b ) . D i s c u s s i o n and C o n c l u s i o n s As a l r e a d y d i s c u s s e d i n o u r p r e v i o u s work (14) on t h e b a s i s o f model c o n s i d e r a t i o n o f A t a l l a ( 1 5 ) and o f H a y a s h i ( 1 6 ) , c o n f o r m a t i o n a l changes a t t h e g l y c o s i d i c l i n k a g e between C - l and C-4 o f t h e c e l l u l o s e c h a i n c a n be assumed t o be t h e predominant cause o f s t r u t u r a l changes i n t h e t r a n s i t i o n cellulose

I^

V

Na-cellulose

> cellulose I I

of native l i n t e r s c e l l u l o s e , the f i r s t step being p a r t i a l l y rever s i b l e a t an a l k a l i c o n c e n t r a t i o n w i t h i n t h e t r a n s i t i o n range. Be s i d e s t h i s , s e l e c t i v e i n t e r a c t i o n s o f t h e d i f f e r e n t OH-groups w i t h NaOH and H2O have t o be t a k e n i n t o account, i n v o l v i n g a d i s t u r b a n c e o r b r e a k down o f t h e Η-bonds o f t h e c e l l u l o s e m o i e t y . Based on t h i s g e n e r a l r e a s o n i n g and on model l ^ C NMR-spectra r e c e n t l y c a l c u l a t e d by Kamide (50 t h e f o l l o w i n g q u a l i t a t i v e i n t e r p r e t a t i o n o f o u r l ^ C NMR and WAXS r e s u l t s p r e s e n t e d h e r e may be proposed: As r e v e a l e d by the t o t a l o r p a r t i a l d i s a p p e a r e n c e o f t h e narrow p a r t o f t h e l i n e a t 89 ppm, t h e s i g n a l b r o a d e n i n g i n t h e C - l , C - 4 , and C-6 r e g i o n and the changes i n t h e WAXS p a t t e r n , t h e i n t e r a c t i o n between c e l l u l o s e and NaOH ( i n aqueous as w e l l a s i n e t h a n o l i c s o l u t i o n ) and a l s o w i t h aqueous guanidonium h y d r o x i d e r e s u l t s i n a l o w e r i n g o f s u p e r m o l e c u l a r o r d e r due t o l e s s dense p a c k i n g o f t h e c h a i n s and/or coexistence o f d i f f e r e n t conformational stages. On r e g e n e r a t i o n , t h i s decrease o f supermolecular order i s only p a r t i a l l y reversed, depending on k i n d o f a l k a l i treatment and p r o c e d u r e o f r e g e n e r a t i o n . The s u p e r m o l e c u l a r o r d e r o f t h e r e g e n e r a t e d samples c a n be i n c r e a s e d by b o i l i n g i n water, as shown e s p e c i a l l y f o r c e l l u l o s e t r e a t e d w i t h guanidonium h y d r o x i d e . Comparing t h e two r e a c t i o n media H2O and EtOH, NMR and X-ray d a t a r e v e a l an onset o f t h i s e f f e c t o f d i s o r d e r i n g a t a much lower NaOH c o n c e n t r a t i o n i n t h e c a s e o f EtOH as compared t o H2O. A c c o r d i n g t o t h e NMR s p e c t r a , t h e s t r u c t u r e o f t h e a l k a l i z e d samples "12% NaOH i n EtOH," "24% NaOH i n H 0 " and an amorphous sample o b t a i n e d by b a l l - m i l l i n g are very s i m i l a r . In t h e c o n c e n t r a t i o n range up t o 8% NaOH i n EtOH o n l y a p a r t i a l d i s o r d e r i n g o c c u r s as shown by t h e s t i l l r a t h e r s m a l l and d i s t i n c t NMR l i n e s . With t h e aqueous system, o n the o t h e r hand, no s t r u c t u r a l changes a t a l l a r e d e t e c t a b l e from t h e l ^ c s p e c t r a i n t h i s range o f NaOH c o n c e n t r a t i o n . This d i f f e r e n t e f f e c t o f NaOH on c e l l u l o s e a t a g i v e n l y e c o n c e n t r a t i o n i n an aqueous medium a t one hand, i n an e t h a n o l i c one a t t h e o t h e r may be con n e c t e d w i t h a d i f f e r e n c e i n component d i s t r i b u t i o n as shown r e c e n t l y i n (17) f o r t h e system c e l l u l l o s e / N a O H / i s o p r o p a n o l / R ^ O . Referring t o t h e model NMR s p e c t r a o f c e l l u l o s e c a l c u l a t e d by Kamide (40, a p r e f e r e n t i a l p e r s i s t e n c e o f t h e O 3 H . . . . 0 5 H - b o n d might be assumed from a comparison o f t h e l i n e p o s i t i o n s f o r C - l and C - 4 f o r t h e Na0H/Et0H/H20-system up t o 8% by weight NaOH. Some i n f o r m a t i o n on the s i t e o f t h e N a O H - c o o r d i n a t i o n i n t h e abovementioned system may 2

1

186

F i g u r e 4a.


CP/MAS-^C-NMR-spectra o f h y d r o l y z e d c o t t o n l i n t e r s powder a f t e r t r e a t m e n t w i t h guanidonium h y d r o x i d e and n e u t r a l i z a t i o n , resp., regeneration. A - regenerated Β - r e g e n e r a t e d and b o i l e d i n water C - o r i g i n a l s t a t e ( o r i g i n a l sample w i t h o u t f o r comparison)

treatment

7A

/ 106

106

F i g u r e 4b.

87

63

7 /

Ϊ

62

CP/MAS-^C-NMR s p e c t r a o f m e r c e r i z e d h y d r o l y z e d c o t t o n l i n t e r s powder a f t e r t r e a t m e n t w i t h guanidonium h y d r o x i d e and n e u t r a l i z a t i o n , r e s p . , r e g e n e r a t i o n . A - regenerated Β - r e g e n e r a t e d and b o i l e d i n water C - o r i g i n a l s t a t e ( o r i g i n a l sample w i t h o u t f o r comparison)

treatment

10.

PHILIPP ET AL


187

be d e r i v e d from a c o m p a r i s o n o f o u r e x p e r i m e n t a l l ^ C d a t a w i t h c a l c u l a t e d s p e c t r a (5^) o f a l k a l i c e l l u l o s e . From t h e p o s i t i o n o f the C-6 s i g n a l a p r e f e r e n t i a l c o o r d i n a t i o n o f N a a t OH-6 might be concluded. F i n a l l y , from a m e t h o d o l o g i c a l p o i n t o f view i t may be s t r e s s e d t h a t t h e c o m b i n a t i o n o f C-CP/MAS-NMR-spec trome t r y and WAXS a g a i n proved t o be a v e r y u s e f u l t o o l i n e l u c i d a t i n g s o l i d s t a t e s t r u c t u r a l changes i n c e l l u o s e . Both methods a r e supplementing each o t h e r i n s o f a r , as WAXS p r o v i d e s i n f o r m a t i o n on t h e i n t e g r a l s t a t i c s u p e r m o l e c u l a r s t r u c t u r e o f t h e sample, w h i l e ^ C s o l i d s t a t e NMR s p e c t r o s c o p y r e v e a l s d e t a i l s o f s t r u c t u r a l changes a t s p e c i f i c s i t e s and a d d i t i o n a l l y c a n p r o v i d e i n f o r m a t i o n o f s t r u c t u r a l dynamics by r e l a x a t i o n measurements. So f a r , t h i s c o m b i n a t i o n has been a p p l i e d t o the c r y s t a l l i n e part o f the c e l l u l o s e s t r u c t u r e mainly, but - as shown by t h i s c o n t r i b u t i o n and by some o f o u r work now i n p r o g r e s s i t a l s o o f f e r s good chances t o g a i n a deeper i n s i g h t i n t o t h e amor phous p a r t o f t h e s t r u c t u r e and i t s r e l e v a n c e f o r m a c r o s c o p i c p r o p erties of cellulose. +

13

Acknowledgment The c o o p e r a t i o n o f Dr. Ho. Dautzenberg, Dr. F. L o t h , and Dr. W. Wagenknect i n s u p p l y i n g t h e samples and o f Dr. Sc. G. S c h e l e r , F r i e d r i c h - S c h i l l e r - U n i v e r s i t a t Jena, i n measuring t h e ^ C NMRs p e c t r a i s g r a t e f u l l y acknowledged.

References 1.

Philipp, B.; Fink, H.-P.; Kunze, J.; Frigge, K. Annalen der Physik Leipzig 1985, 42, 507-23. 2. Kunze, J.; Ebert, Α.; Schröter, Β.; Frigge, K.; Philipp, B. Polymer Bulletin 1981, 5, 399. 3. Kunze, J.; Scheler, G.; Schröter, B.; Philipp, B. Polymer Bulletin 1983, 10, 56. 4. Kamide, K.; Okajima, K.; Kowsaka, K.; Matsui, T. Polymer J. 1985, 17, 701. 5. Kamide, K.; Kowsaka, K.; Okajima, K. Polymer J. 1985, 17, 707. 6. Makarenko, M. V.; Gert, Ε. V.; Kapuckij, F. Ν. Z. Prikl. Chim. 1982, 55, 2542. 7. Schröter, B. Dissertation A, Friedrich-Schiller-Universität Jena, 1982. 8. Atalla, R. H.; Gast, J. C.; Sindorf, D. W.; Bartuska, V. J.; Maciel, G. E. J. Amer. Chem. Soc. 1980, 102, 3249. 9. Purz, H. J.; Fink, H.-P. Acta Polymerica 1983,34,546. 10. Fink, H.-P.; Fanter, D.; Philipp, Β. Acta Polymerica 1985, 36, 1. 11. Fink, H.-P.; Fanter, D.; Loth, F. Acta Polymerica 1982, 33, 241. 12. Kunze, J.; Scheler, G.; Sternberg, U.; Philipp, B. Acta Poly merica in press. 13. Fink, H.-P.; Philipp, B.; Serimaa, R.; Paakkari, T. Publica tion in preparation. 14. Fink, H.-P.; Philipp, Β. J. Appl. Polymer Sci. 1985, 30, 3779.

188 15. 16. 17. 18.

THE

STRUCTURES OF

CELLULOSE

Atalla, R. H. J. Appl. Polymer Sci., Appl. Polymer Symposium 1983, 37, 295. Hayashi, J. Sen-i Gakkaishi 1976, 32, 37. Yokota, H. J. Appl. Polymer Sci. 1985, 30, 263. Lindberg, J.; Hortling, B. Advances in Polymer Science 66, 2-10, Springer Verlag Berlin-Heidelberg, 1985.

RECEIVED March 5,

1987

The Structures of Cellulose - American Chemical Society

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