Iminodiacetic acids based on vinylamine-vinylpyrrolidone copolymers

Iminodiacetie acids

3081

43. 44. 45. 46.

(l. HENRI(II-OLIV]~ and S. OLIVIa, Makromolek. Chem. 96: 221, 1966 11. lil. SCOTT and E. SEN0(ILES, J. Macromolec. Sci. C9: 49, 1973 G. 1H. BURNETT and Y. D. LOAN, Trans. Faraday Soc. 51: 219, 1955 C. It. BAlYl~ORD, A. D. JENKINS and It. JOHNSTON, Trans. Faraday Soc. 55: 1451, 1959 47. Yu. B. ~ I K , Dissertation, 1974 48. Ye. S. GARINA, T. M. KUZNETSOVA, V. P. ZUBOV and V. A. KABANOV, Dokl. AN SSSR 209: 380, 1973; G. S. GEORGIYEV, A. N. KAPLAN, V. P. ZUBOV, V. B. GOLUBEV, I. lH. BARKALOV, V. I. GOL'DANSKII and V. A. KABANOV, Vysokomol. soyed. A14: 177, 1972

IMINODIACETIC VINYLAMI

ACIDS BASED

-VINYLPYRROLIDONE

ON

COPOLYMERS*

L. I. TIKHONOVA, O. I. SA~OILOVA, YE. F. ]~ANARIN a n d V. G. YASHUNSKII Biophysics Institute

(Received 6 September 1972) Water-soluble high-molecular iminodiacetic acids have been synthesized by the carboxsrmethylation of vinylamine-vinylpyrrolidone copolymers in an aqueous alkaline medium. The acid-base properties of the synthesized polymeric acids have been studied potentiometriely. Their dissociation constants have been determined at an ionic strength of 0'1 (NaNO3) at 20°C. SYI~'THETIC h i g h - m o l e c u l a r c o m p o u n d s h a v i n g c o m p l e x i n g p r o p e r t i e s are c u r r e n t l y finding wide use. I n this field, t h e r e is g r e a t interest in water-soluble p o l y m e r i c c o m p l e x o n e s , d e r i v a t i v e s of a - a m i n o a c e t i e acids, whose m o n o m e r i e a n a l o g u e s are c h a r a c t e r i z e d b y t h e a b i l i t y to f o r m stable chelates w i t h m a n y m e t a l cations in a q u e o u s solutions. H o w e v e r , o n l y different p o l y m e r i c c o m p l e x o n e s are k n o w n in t h e l i t e r a t u r e , p r i n c i p a l l y i o n - e x c h a n g e resins or o t h e r p r o d u c t s insoluble in w a t e r [1, 2]. W e h a v e o b t a i n e d w a t e r - s o l u b l e p o l y m e r i c iminodiaeetic acids b y t h e carb o x y m e t h y l a t i o n of e o p o l y m e r s f o r m e d b y v i n y l a m i n e a n d N - v i n y l p y r r o l i d o n e [3] w i t h v a r i o u s s t r u c t u r e s a n d w i t h m o l e c u l a r weights of (8-10) × 103, (33-35) × )< 10 a a n d ( 9 6 - 1 0 0 ) × 10 s. P o t e n t i o m e t r i c t i t r a t i o n was u s e d to d e t e r m i n e t h e i r dissociation c o n s t a n t s a t a n ionic s t r e n g t h of 0.1 (NaNOs) a t 20°C. A solution of t h e c o p o l y m e r in w a t e r was a d d e d to m o n o c h l o r a c e t i c acid, t a k e n in excess, n e u t r a l i z e d w i t h alkali. A solution of 6 N K O H was a d d e d d u r i n g * Vysokomol. soyed. A16: No. 12, 2646-2650, 1974.

3082

L. I. TIKHOI~OVA e~ al.

stirring and heating to 80-90°C in order that the 10H of the reaction medium should be 10-11. After being held for 24 hr at room temperature, the solution was subjected to electrodialysis with ion~xchange membranes MA-40 and MK-40 (working voltage, 70 V). The dialysate was evaporated to dryness, the.residue was treated with alcohol and the polycomplexone was dried in vacuum over P205. Three polyvinylpyrrolidonepolyvinyliminodiacetic acids I - I I I were synthesized (Table 1). TABEE

l.

CONDITIONS OF SYNTHESIS~ YIELD AND COMPOSITION OF COMPLEXONES

I Complexone

t m >c10 -a

I I II III

1.75 8-10 3 33--35 1"75 96--100

Starting substance8 copo-

chloracey~ter, tie, g

15.3" I 7.58 10-2" 6"0 4.87 2"83 I

Yield

6

Found, %

corn-

KOH,mlone, g 27 22 10

16.4 9"1 2'2t

I Calculated % Gross formula of monomeric link

C

H

52.8 58.3 49.0

7.44 7'89 7'76

L

I C,0HgDI~I~OH'THsO Cs4HsaN.Olo'SHtO Cs4Hs.l%0~o'12HsO

°

H

52-0 52'8 48'6

7'28 7"75 7'54

* Copolymer taken as the chlorhydrate. t Starting substance sparingly soluble, and the reaction "therefore takes place incompletely.

Potentiometric titration was carried out with a LPU-01 pH-meter with glass and calomel electrodes, which has been carefully calibrated beforehand, in a cell in a nitrogen atmosphere with stirring. 2 × 10 -8 and 4X 10 -3 M aqueous solutions of the polymeric acids in 0.1 M NaNOs were titrated with an 0.1 M solution of N a O H in an 0.1 ~ solution of NAN08. In the first region of neutralization the titrations were thus carried out b y the usual version of the method, and in the second region b y the method of "step-wise" titration [4], that is, after each addition of an 0.1 equivalent quantity of the alkali, the solutions were stirred for 5-10 days until equilibrium was reached. After being dried to constant weight, the complexones I - I I I are obtained as hard substances, light yellow in colour, containing water of crystallization, in which practically no free amino groups m a y be determined. On the basis of the data from chemical analysis and the characteristics of the potentiometric titration curves, as well as from the rate at which equilibrium is established in the neutralization reaction (equilibrium is established almost instantaneously in the first region, but in 5-10 days in the second region) the structure of iminodiacetic derivatives m a y be assigned to the polymeric compounds:

/N\

0

N+

Iminodiacetie acids

3083

Another confirmation of the presence of aminodiacetie groups in complexones I - I I I is the sharp extreme values at a z 1 on the differential titration curves (a is the number of moles of alkali added per mole of polymeric acid groups being titrated). The equivalent weights of the synthesized polymeric acids I - I I I were determined potentiometricly [4]; the follow ng values were found: 381-4-8; 5 4 7 ~ 12 a n d 411 =L8, corresponding to values of m of 1.75, 3 and 1.75 respectively. log Z -.~ ¢X-!

-o-~ 0 o,q 0.6 pH:

I

')"

I

)

I

'

pH

.q'O 0 1

8.7 q'2 7.q

3"8 6.6

3.q O=

-O'q

L7

T

o.q

log .I ~/z

Acid I: /--dependence of (1--a)/a and 2--(2--a)/(a--1) on pI-I.

The dissociation constants K~, and K=, were calculated from the potentiometric titration curves by two methods, by the method of Bjerrum and Schwarzenbach [5, 6] and from the Henderson-I-Iasselbach equation modified by us: p t t - - - - p K a - - n ' log

pH=pKa--n"

-

-

2--0C cz--I

log-

The constants

[H+] [HX-] K1

-

-

[H+] [X~-] K2 ----

[~2X]

[HX-]

,

were calculated by the first method in a similar fashion to the monomeric iminodiacetie acids, H X - and X 2- being the anions of the acids H2X. I n the case of polymeric acids, however, the dissociation constants are known to depend on the charge z on the monomeric link [4, 7] and as a measure of this we take the ratio of the concentrations of charged and uncharged groups K a = K . f ( z ) , where f ( z ) - ~ z n-1 and n is a coefficient. I n this version of the calculation, therefore, curves of p H as a function of log

-

-

and p H as a function of log - -

are

3084

L.I.

Tn~HO~OVA et

al.

TABLE 2. I)ISSOCIA~'m~ cO~STX~rrs FOR POLYMERIC IM/NODIACETIC ACIDS I - I I I

K1 x IO~/K x lO s

Ka, × lOt/ /Ka. X IO s (first m e t h o d )

PKa,/PKa. (second m e t h o d )

Acid I 0-0997 0-1997 0.3002 0.4011 0.5023 0.6040 0-7061 0.8084 0.9112 1.0146 1.1181 1.2222 1.3266 1-4314 1.5366 1-6423 1.7484 1.9558

3-05 3"13 3"23 3"35 3"48 3"65 3"87 4"18 4"77 5"80 6"91 7"17 7-54 7.82 8"17 8"72 9"06 9"41

9"90 9-24 8.29 7.29 6"46 5"40 4.33 3"50 28-2

4"10 3"80 3"63 3"54 3"48 3"44 3"45 3"49 3"65

0"78 1"57 2-21 2"67 3"03 3-10 2"96 2"77 25.4

8.85 8.37 8.08 8.06 8.02 8.06 8.30 8.25 7.11

2"51 1"78 2.21 1"69 1"77 1-04 0.47 0"37 1"46

2"49 1"65 1"93 1"40 1"39 0"78 0"34 0.25 0"93

Acid II 0.1009 0.2023 0.3041 0.4064 0-5089 0.6119 0.7154 0.8190 0.9232 1.0279 1.1328 1.2382 1-3440 1-4502 1.5568 1.6639 1.7714 1.8790 1.9873

2"96 3"03 3"12 3"24 3"38 3"57 3"90 4"50 5"58 6"39 7"09 7"40 7"56 7.76 8-09 8"46 8.77 8-87 9.01

4'00 3"67 3-52 3"42 3-36 3"35 3"46 3"78 4.39

1"67 3.42 4.17 4"70 4"93 4"55 3"04 1.28 0.36

19.2 19.8 15-6 12.7 10.4 7.8 4.4 1.6 0"4 1-18 1"25 1.24 1 "44 1"52 1 "02 0"69 0"94 0.91 5.38

1"19 1"31 1 "36 1"63 1"78 1"22 0"85 1"19 1"19 7"17

9"19 8"25 8"12 7"96 7"88 7"95 8"04 8"02 7"65 6"32

3085

Iminodiacetic acids TABLE 2

(cont.) Ka, x 10B/

pH

Kx × 104/K×

10 s

/Ka, X l 0 s (first m e t h o d )

pKa,/pKa, (second m e t h o d )

Acid III 2"98 3"07 3"17 3"30 3"45 3"66 3"97 4"45 6"05 7"08 7"65 8"08 8"29 8-40 8.52 9.08 9.44 9"67

0'1041 0.2086 0"3136 0"4190 0.5247 0"6309 0"7376 0.8445 0"9519 1"0599 1"1680 1"2767 1"3858 1"4953 1.6052 1.7156 1.8264 1"9374

4"02 3"71 3"54 3"46 3"40 3"40 3"48 3"74 4"62

1"27 2'64 3"63 3'92 4"05 3"81 3"02 1 '82 0"19

15"3 14'8 13"0 10"2 8"2 6"3 4"2 2'2 0"2

0'54 0"47 0"34 0"35 0"44 0"52 0"24 0"21 0"39

0"53 0"44 0"32 0"32 0"39 0"46 0"20 0'17 0"31

8"65 8"56 8"63 8"55 8"56 8"55 8"56 8"55 8"13

plotted (see Figure), which enabled the coefficients n' and n" to be determined. The constants Ka, and Ka, were then calculated from the equations: K a = K 1.z ~' and Ka, K 2 • Z n ' ' - I • I t was found that the value of Kal agrees well with those obtained from the Henderson-Hasselbach equation, if the formula mentioned is used b u t n o t with the coefficient n ' - 1. The data from one titration are shown in Table 2 as an illustration and the average values of the dissociation constants determined from 4 or 5 parallel titrations are given in Table 3; for comparison, Table 3 also gives constants for analogues of the synthesized complexones, namely, Dowex ~

TABLE

3. A V E R A G E V A L U E S OF T H E D I S S O C I A T I O N COI~STANTS OF P O L Y M E R I C I M I I ~ O D I A C E T I C ACIDS

Acid I II III D o w e x A-1 r e s i n fl-Phenylethylimindiacetic

n'/n" 1.11/1.67 1.10/1.42 1.10/1.31

pKa~

pKa~

3.38~0.04 3.30±O.O8 3.32±0.08 2-77--2.92 2.66

8.1~0.1 7.9~0.1

8-6~0.1 8.55 [8, 9] 9.18 [10]

3086

L. I. TIK~ONOVA e$ al.

A-1 resin containln~g iminodiacetic groups and fl-phenylethyliminodiacetic acid. It follows from the data presented that the polymeric complexones, like the monomeric iminodiacetic acids, have a betaine structure, since the values of pKa, are low and the characteristics of the pKa, figures clearly reflect the shedding of a betaine proton. The values of the constants pK~, and pK~, are generally similar to those of the monomeric acids (Table 3). A certain difference between the values of the constants may be explained by electrostatic effects in the polymers, namely, a continuous change in the potential in the polymeric chain and also the possibility of forming hydrogen bonds between unchanged carboxyl groups. The complexones synthesized have approximately the same values of pK¢ and pK~,, except that the values of pKa, vary slightly depending on the composition and structure of the elementary link, a fact which is evidently connected with a reduction in the basicity of the iminodiacetate nitrogen under the effect of an increase in the number of pyrrolidone residues in the polymeric link. A lower value of pKa, is therefore obtained for acid II with a larger number of pyrrolidone links. It is also probably possible to point to some effect of the degree of polymerization since a very high value of pK~, is obtained for polymer III. This is in good agreement with the literature data for monobasic polymeric acids [7, 11]. In addition to this, it is understandable (Table 3) that both constants for the acids studied should approximate to the constants for Dowex A-1 resin containing iminodiacetic groups. It may be seen from Table 2 that the values of pK~, and pK~, vary little for the three polymers studied as the charge on the monomer link or the degree of neutralization increases. Thus the values of p/i~, decrease by 0.2-0.3 units as the value of ~ increases from 0.1 to 0.7-0.8, remaining practically constant in the range a----0.3-0.7 and for a~0.7-0.8 the values increase somewhat. The values of pKa, hardly changed at all for a----1.1-1.7 (1.8), and thereafter decreased appreciably. This is evidently connected with the fact that, in the range =0.8-1.0 and 1.8-2.0, it is difficult to apply the concepts of Bjerrum and the Henderson-Hasselbach equation, possibly because of the strong interactions between adjacent groups [7, 12, 13]. The small variation in the dissociation constants as a function of charge may probably be explained by the presence of steric hindrances. It is important to emphasize that all values of the coefficients n' are found to be approximately the same, whereas those for the coefficients n" differ, as is the case for pKa, and pKa. The value of n" evidently depends on the composition and structure of the elementary link. It should once more be noted in conclusion that the acid-baaic functions of the polymeric iminodiacetic acids studied approximate to those of the mehomeric analogues. Translated by G. F . M O D ~

Effect of y-radiation on structural ordering of P E

3087

REFERENCES

1. R. HERING, Zhelatoobrazuyushchiye ionoobmenniki (Gelatinous Ion-Exchange Materials). Izd. "'Mir", 1971 (Russian translation) 2. S. S. SKOROKHODOV and A. A. VANSHE1])T, Vysokomol. soyed. 2: 1405, 1960 (Not t r a n s l a t e d in P o l y m e r Sci. U.S.S.R.) 3. Ye. F. PANARIN and S. N. USHAKOV, Khim.-faxmakol. zh. 5: 28, 1968 4. G. K. HOSCHELE, J. B. ANDELMAN and H. P. GREGOR, J. Phys. Chem. 62: 1239, 1958 5. JANNIK BJERRUlVI, Obrazovaniye aminov metallov v vodnom ~astvore. Teoriya o b r a t i m y k h s t u p e n e h a t y k h reaktsii (Formation of Metal Amines in Aqueous Solution. Theory of Reversible Stepwise Reactions). Izd. inostr, lit., 1961 (Russian translation~ 6. G. SCHWARZENBACH, I-Ielv. chim. a c t a 38: 1147, 1955 7. H. P. GREGOR, L. B. LUTINGEI~ and E. M. LOEBL, J. Phys. Chem. 59: 34, 1955 8. $. KRASNEI~ and J. A. MAItINSKY, J. Phys. Chem. 67: 2559, 1963 9. D. E. LEYDEN and A. L. UNDERWOOD, J. Phys. Chem. 68: 2093, 1964 10. I. D. KISELEVA, L. I. TIKHONOVA, L. L IVANOVA and V. G. YASHUNSKIT, Zh obshch, kbimii 41: 2599, 1971 11. H . P . GREGOR, L. B. LUTINGER and S. M. LOEBL, J. Phys. Chem. 59: 366, 1955 12. IV[. TEYSSIE a n d P. TEYSSIE, J. Polymer Sei. 1: 253, 1961 13. P. TEYSSIE, K h i m i y a i tekhnol, polimerov 9: 3, 1966

EFFECT OF ~-RADIATION ON THE STRUCTURAL ORDERING OF POLYETHYLENE* G. D . KORODE~KO, S. N . KARIMOV a n d A . SULTAI~/OV V. I. Lenin T a j i k State University

(Received 17 November 1972) I t has been shown b y I R spectroscopy t h a t a non-equilibrium supermolecular structure, which becomes more perfect during subsequent heating, is formed in tile 7-irradiation of P E in the presence of oxygen.

IT U S been shown previously [1] that, when low-density polyethylene (PE) is irradiated with ~-rays in the presence of a limited amount of atmospheric oxygen, a complex reorganization of the molecular and supermolecular structures, which changes the properties of this material, occurs in the material as a result of radiation-chemical processes of-degradation and crosslinking. Irradiation oi P E by ~-rays in vacuum leads to the formation of a spatial network, an increase in the number of double bonds and a reduction in the degree of crystallinity [2-4]. When P E is irradiated in air, oxygen, by diffusing preferentially into amorphous regions, interacts with free radicals and this leads to the formation * Vysokomol. soyed. A16: No. 12, 2651-2654, 1974.