Some structural studies on highly substituted cellulose cyanoethylates (CCE)

1762

I . N . KIM et al. REFERENCES

1. Ts. M. LEVITSKAYA, Dielektricheskie poteri i polyarizatsiya epoksidnykh smol razlichnoi struktury. Sb: Sibir. N I I E , vyp. 16, pod red. Yu. N. Vershinina (The Dielectric Losses and Polarizations of Epoxide Resins of Different Structure. In: Sibir. N I I E 16: Yu. N. Vershinin, editor), p. 154, Izd. "Energiya", 1970 2. F. It. DAMMONT and T. K. KWEI, J. Polymer Sci. 5, A-2: 961, 1967 3. G. P. MIKHAILOV, A. I. ARTYUKHOV and T. I. BOItISOVA, Vysokomol. soyed. B9: 138, 1967 (Not translated in Polymer Sci. U.S.S.R.)

SOME STRUCTURAL STUDIES ON HIGHLY SUBSTITUTED CELLULOSE CYANOETHYLATES (CCE)* I. N. KIM, T. SAIDALIEV,V. I. SADOVNIKOVA,Yr. T. TASHPULATOV, T. G. GAFUROVand KH. U. USMA~OV Cotton Cellulose Chemical and Technical Research I n s t i t u t e (Received 12 M a y 1969)

MUCH attention has been given by investigators to the partly substituted cellulose cyanoethylates (CCE) because of t h e relatively simple production method, and the technically important properties, of which the most noticeable is the dielectric constant, and also the larger heat-, biological- and light-resistance, and the adhesion capacity. The limited solubility and the severe processing conditions, however, are an obstacle to their practical application in, for example, the production of films, fibres and plastics. We eliminated these deficiencies by synthesizing a highly substituted CCE based on cotton cellulose; the degree of substitution, ~c~----296, made the product soluble in the usual organic solvents, such as acetone, methyle~.e chloride, acetonitrile, dimethylformamide (DM-F), a methylene chloride mixture with alcohols, etc. There is hardly any reference to be found in the literature to the structural study of highly substituted CCE. This report describes the X-ray and infrared study of the structural changes which occur in cotton cellulose on changing from the natural product to the highly substituted CCE; addition work dealt with sorption properties and the density. EXPERIMENTAL The s t u d y objects were CCE samples with different degrees of substitution, amongst them also those with ~c~----296, which were produced as outlined earlier [1]; they were all * Vysokomol. soyed A12: No. 7, 1550-1554, 1970.

Some structural studies on highly substituted cellulose cyanoethylates

1763

carefully freed of salts by washing, were extracted with methanol and reprecipitated from acetone. The X-ray scattering diagrams were produced on instrument URS-50 IM. The samples were produced by pressing the already pulverized and sieved samples at 8-10 tons/cm~; these tablets were 3 cm in diameter and were examined in monochromated light from a CuK~ source [2]. The infrared absorption spectra of the highly substituted CCE were recorded on instrunwnt UR-10 in the range 3800-2000 em -1, using a lithium fluoride prism and the known method [31]. The intensity of the hydroxyl groups included in the hydrogen bond was established by measuring the peak area of the curve plotted on the basis of optical density (D) calculations (Son, cm 2) at frequencies of 3000-3720 cm -1, using a planimeter. As the 2250 em -~ absorption line is very sensitive to the quantitative content of nitrile groups in the samples, the line intensity (Ic~, ram) was assessed directly on the infrared spectra. The moisture absorption of CCE was determined on a MacBain vacuum sorption instrument [4]. The density was determined in a 1 : 1 mixture of p-xylene and toluene by the gradient column method. RESULTS

T h e s t r u c t u r e of t h e cellulose fibre is k n o w n to be c h a r a c t e r i z e d firstly b y t h e presence of o r i e n t e d zones, where the i n t e r m o l e c u l a r r e a c t i o n s b e t w e e n O H - g r o u p s are strong, a n d s e c o n d l y b y t h e presence of less o r d e r e d zones w i t h w e a k interm o l e c u l a r reactions. T h e O H - g r o u p s p r e s e n t in cellulose are s t r o n g l y p o l a r a n d c h e m i c a l l y reactive, so t h a t v a r i o u s chemical a n d p h y s i c a l effects will cause s t r u c t u r a l changes, changes in t h e r a t i o of o r i e n t e d to less o r i e n t e d zones, etc. I t was t h e r e f o r e i n t e r e s t i n g to find o u t h o w t h e s t r u c t u r e changes on increasing the degree of O H - g r o u p s u b s t i t u t i o n b y c y a n o e t h y l g r o u p s in t h e m a c r o m o l e c u l e . E a r l i e r e l e c t r o n - m i c r o s c o p i c studies h a d s h o w n [5] different s t r u c t u r e s in t h e t h i n sections of the original, c o m p a r e d w i t h c y a u o e t h y l a t e d cellulose; these differences were larger w h e r e t h e s u b s t i t u t i o n was higher. T h e u n i f o r m d i s t r i b u t i o n of the s e c o n d a r y wall in t h e t r a n s v e r s e cross-section t h r o u g h a c y a n o e t h y l a t e d fibre shows t h e process to be u n i f o r m , a n d we were t h e r e f o r e i n t e r e s t e d in t h e result of X - r a y a n d i n f r a r e d studies of t h e CCE s t r u c t u r e . T h e results of the X - r a y a n d infrared studies clearly s h o w e d a n increase of t h e difference on increasing t h e degree of s u b s t i t u t i o n of O H b y c y a n o e t h y l groups, especially on c h a n g i n g to t h e highly s u b s t i t u t e d s a m p l e s which are soluble. T h e X - r a y s c a t t e r i n g p i c t u r e s s h o w e d (:Fig. 1) t h a t c h a n g i n g f r o m t h e original fibre (sample 1) to t h e c y a n o e t h y l a t e d (samples 2-5) caused a g r a d u a l r e d u c t i o n of the p e a k reflections intensities in t h e r a n g e of angles 2 0 = 1 4 - 1 6 ° a n d 22 °. ]~~()r e x a m p l e , t h e X - r a y d i a g r a m of s a m p l e 3 w i t h 7oN= 103.8 (N=6.7~/o) shows a reflection p e a k a t 2 0 = 1 4 - 1 6 ° fused into a single p e a k , while t h a t of s a m p l e 4, ycx-=177"3 ( N = 9 " 7 ~ o ) h a s a l m o s t none, a n d t h a t a t 2 0 = 2 2 ° b e c a m e b r o a d e r , a l t h o u g h t h e i n t e n s i t y diminished. T h e n a t u r e of t h e reflection p e a k of s a m p l e 5, 7CN= 218" 1 (N = 11.0 %) differed g r e a t l y f r o m t h a t of t h e original cellulose, which i n d i c a t e ( / t h a t a n e w s t r u c t u r e f o r m e d in t h e studied samples. I t m u s t be e m p h a s i z e d t h a t s a m p l e s 6 a n d 7 g a v e a n e n t i r e l y different X - r a y s c a t t e r i n g picture; t h e r e was a n e w p e a k a t 2 0 = 1 0 ° 3 0 ' a n d the p e a k a t 2 0 = 2 2 °

1764

I.N. KTM et al.

60

~1 qo ~--~

Ù L

1

1

1

z

I

10 20 30

I

I

0

I

I

I

10 2.0 30

0

I

70 20 30 20

3O

70~

•~

O I

80[

2.

I

I

f

I

I

i

r

3 f'~r

50

2L/003000 ZSO0 ZZGO 3#00 3000 ZSDO 22Qg i~oQm-r FIG. I. X-ray scattering diagrams (a) and infrared spectra (b) of CCE: 1--natu#al

cellulose, 2-7--CCE samples containing 2.0, 6.7, 9.7, 11.0, 12.5 and 13.0°/o N respectively. became quite diffuse. The shape of this curve is reminiscent of cellulose triacetate and indicates t h a t a new structure is present in the highly substituted CCE samples with 7c~----274.5-296.2 [6]. The above-mentioned changes in the appearance of the X-ray scattering diagram are obviously due to the macromolecules in planes 101 and 101 moving apart at the start of cyanoethylation, and subsequently in plane 002; this results in the destruction of the original cellulose structure and the appearance of a new one, typical of the highly substituted CCE. The results of infrared spectroscopy are shown in Fig. lb. The change from the natural to the highly substituted cellulose produced a gradual decrease of the

Some structural studies on highly substituted cellulose eyanoethylates

1765

O H - g r o u p line i n t e n s i t y where involving the h y d r o g e n bond, a decrease of the half-width o f this line, a n d also a p e a k displacement t o w a r d s larger frequencies. The l a t t e r is evidence of a g r a d u a l w e a k e n i n g of the h y d r o g e n bonds, and of a larger degree of substitution. The calculated surface areas u n d e r the a b s o r p t i o n line of O H - g r o u p s included in h y d r o g e n bonds (Soil; Table 1) also b e c a m e smaller, which again indicated a TABLE 1. THE CHARACTERISTICSOF CCE

Sample No.

~-eontent,

7e~

Peak intensity of CNgroups,

SOIcI cm 2

o o

Peak Sample No.

/o

0 9.0 24.5 26.5

42.5 33-0 27.0 I1.4

intensity

ef CNgroups, IFIII1

!l i

0 25-0 103.8 177.3

Yc_n

S oK, era2

o/

inln

Control 2.0 6.7 9.7

N-content,

. . . .

1--

5 6

II

7

218.1 274"5 296.2

ll.0 12.5

1,3.0

11'5 5.0 4.0

28.4 34.0 36.0

decrease in the n u m b e r of h y d r o x y l groups. The line i n t e n s i t y of the CN-groups in the region of 2250 cm -1 increased a t the same time as a f u n c t i o n of the degree of substitution. Table 1 also contains t h e line intensities of CN-group a b s o r p t i o n in millimetres. T h e increased i n t e n s i t y of the CN-group a b s o r p t i o n lines a n d the decrease of t h a t of OH-groups, as well as the absence of a b s o r p t i o n lines for the C = C bond in the i n f r a r e d s p e c t r u m , is evidence o f CCE forming as a result of e x p e n d i t u r e OH-groups present in the maeromolecules as well as the C = C bonds of acrylonitrile. T h e Table also shows t h a t Soil becomes smaller while the N - c o n t e n t increases a n d the line i n t e n s i t y of the CN-group in CCE becomes greater. The Soil in em 2 and the line i n t e n s i t y (Ic~, ram) of CN-group a b s o r p t i o n is shown as a f a n e t i o n of N - c o n t e n t (%) in Fig. 2; these functions are linear a n d t h e N - c o n t e n t of CCE can t h e r e f o r e be d e t e r m i n e d w i t h reasonable a c c u r a c y b y infrared spectroscopy°

t•ott•Cm2

rCNf i7,'~

2 ~i

3

5

7

I

oo N, %

I

11

I

I

13

Fie'. 2. Soil and peak intensity (Iex) as a function of the nitrogen content of CCE.

1766

I.N. KIM et

al.

The internal stabe of the cellulose structure and that of its esters can be characterized to a large extent b y its hygroscopic nature and density. The presence o f any sorbed liquid is known to affect the chemical and electrical properties of cellulose preparations [7]. The moisture uptake of partly cyanoethylated cellulose, 7CN= 150, studied in earlier work, showed hydrophobic cyanoethyl groups to reduce the hygroscopieity of CCE [4]. This was confirmed in subsequent studies of more highly substit u t e d CCE (Fig. 3) on samples having 7cN=177.3, 221.5, 287.3, and respective % !

8!

/2-

/-"//i" 2

~

I

I

I

zo qo 80 80 Relaffve hurn/d/f~ , %

I

1oo

FIG. 3. Humidity sorption isotherms for CCE: /--control (natural cellulose), CCE samples containing 9-7, 11.1 and 12.8% N respectively.

2-4--

N-contents of 9.7, 11.1 and 12.8. The higher the degree of substitution, the looser becomes the structure, and the density diminishes (Table 2); the reduction of the hygroscopicity can be explained only b y the partial or complete substitution of hydroxyl groups b y the hydrophobic cyanoethyl groups. TABLE

Sample 1NTo.

2. DENSITY

N-content, % Control 6.15 8.30

CHANGES IN

?c~ 0 92.8 140.0

CCE

Density, g/era8 1-5500 1.4020 1.3250

AS A F U N C T I O N

Sample No. 4 5 6

OF N I T R O G E N C O N T E N T

N-content, %

~c~

Density, g/cm~

11.0 12.0 12.9

218.0 254.0 292.0

1.2835 1.2290 1.2060

The results reported here show good correlation of the data obtained b y differe n t methods. CONCLUSIONS

(1) The results of X-ray scattering, spectroscopic and other studies have established structural differences to occur on changing from natural to highly substituted cellulose cyanoethylate (CCE).

Calorimetric s t u d y of steric network production

1767

(2) The infrared spectroscopic data So~ and the nitrile group absorption lines were found to be linear functions of the N-content of CCE; the degree of orientation, density, and the sorption capacity of the samples was decreased by the substitution. (3) H i g h l y s u b s t i t u t e d CCE, ycN~--274.5-296.2, h a v e a n e w s t r u c t u r e .

Translated by K. A. ALLE~ REFERENCES 1. I.N. KIM, V. I. SADOVNIKOVA, N. V. VOSTRILOVA, A. M. ZARIPOVA and Kh. U. USMANOV, Uzbek. khim. zh., No. 6, 56, 1968 2. T. SAIDALIEV, Yu. T. TASHPULATOV and Kh. U. USMANOV, Uzbek. khim. zh.. No. 6, 31, 1965 3. Kh. U. USMANOV, T. SAIDALIEV and Yu. T. TASHPULATOV, Sb.: K h i m i y a i fizikok h i m i y a p r i r o d n y k h i sinteticheskikh polimerov (In: The Chemistry and Physical Chemistry of N a t u r a l and Synthetic Polymers). Issue No. 2, p. 5, Izd. Akad. N a u k Uzbek. S.S.R., Tashkent, 1964 4. Kh. U. USMANOV, V. I. SADOVNIKOVA and I. Kh. KRAKIMOV, Dokl. Akad. N a u k Uzbek. S.S.R., No. 5, 43, 1962 5. K. Kh. RAZIKOV, V. I. SADOVNIKOVA and Kh. U. USMANOV, Vysokomol. soyed. B9: 822, 1967 (Not t r a n s l a t e d in Polymer Sci. U.S.S.R.) 6. Y. N. NIKITIN and N. V. MIKHAILOV, Sb.: Tsellyuloza i eye proizvodnye (In: Cellulose and its Derivatives). p. 40, Izd. Akad. N a u k SSSR, 1963 7. K h . U. U S M A N O V , S. N. K O L E S O V , V. I. SADOVNIKOVA and~ B. Ye. BAKLITSKII, Dokl. Akad. N a u k Uzbek. S.S.R., No. 3, 25, 1963

CALORIMETRIC S T U D Y OF STERIC N E T W O R K P R O D U C T I O N * T. E. LI1)ATOVAand S. A. ZU~KO I n s t i t u t e of the Chemistry of Macromolecular Compounds, Ukr. S.S.R. A c a d e m y of Sciences

(Received 12 May 1969)

THE process of steric network formation in polymers is accompanied by the formation of branched macromolecules of varying degrees of complexity. Flory [1] suggested the theory of a broad degree of complexity existing in the molecular chain distribution. The larger macromolecular complex formed appear to become the centre around which the steric structure forms (micro-gel). The reaction system becomes structurally heterogeneous after a certain conversion is reached; it can be assumed that the system is then divisible into two phases (sol-gel) owing to micro-incompatibility, i.e. that the system becomes micro-heterogeneous. * Vysokomol. soyed. A12: No. 7, 1555-1559, 1970.