Synthesis and properties of hydrolyzed polymers of maleic anhydride

Polymer Science U.S.S,R. Vol. 25, No. 9, pp. 2254-2258, 1983 l'rinted jn Poland

0032-3950[83 $10.00+.00 © 1984 Pergamon Press L t d .

SYNTHESIS AND PROPERTIES OF HYDROLYZED POLYMERS OF MALEIC ANHYDRIDE* V. ]~. MISHCHE~IKO, V. A. ZUBOV a n d V. A. YEVDOKIMOV ~/[. V. Frunze State University, Simfcropol

(Received 22 2'ebruary 1982) Results are presented of investigations into hydrolysis of copolymers of maleie anhydride with styrene, n-butylmethacrylate and ternary copolymers, pKal and pKa~ vahies were determined for hydrolyzed copolymers. On the basis of pK,, values in a number of systems and based on results of dcrivatographic investigations of a hydrolyzed terpolymer a conclusion was drawn about the preferred position of maleie anhyd'rido units in the terpolymer between styrene and n-butylmethacrylate units. I-[YDROLYZED CO- a n d t e r p o l y m e r s of maleie a n h y d r i d e (lVIAI) n o w a t t r a c t the continuous a t t e n t i o n of m a n y scientists [1-4]. This is due to t h e f a c t t h a t t h e s e p r o d u c t s are polyelectrolytes w i t h a n u m b e r of v a l u a b l e And interesting p r o p e r ties a n d r e p r e s e n t basic c o m p o u n d s for o b t a i n i n g biostable coatings. H y d r o l y s i s of MA1 m a y t a k e place s p o n t a n e o u s l y a t r o o m t e m p e r a t u r e b y t h e action of a t m o s p h e r i c w a t e r v a p o u r [5, 6] b u t this process is v e r y l e n g t h y . I n order to accelerate hydrolysis [3], the reaction is carried o u t using dilute solutions of hydrochloric acid, while in an earlier s t u d y [2] b y saponification w i t h dilute solutions of alkalies a t 393-573°K for 1-5 hr with s u b s e q u e n t t r a n s f e r of the polym e r f r o m the saline into the acidic f o r m b y t r e a t m e n t w i t h strong acids. I f MA1 c o m o n o m e r s during hydrolysis can also be subjected to chemical action, t h e process is considerably complicated. Thus, during saponification of the cop o l y m e r of maleic a n h y d r i d e w i t h v i n y l a c e t a t e (VA) followed b y t r e a t m e n t w i t h acids a h y d r o l y z e d c o p o l y m e r w i t h an e q u i v a l e n t c o n t e n t of e a r b o x y l g r o u p s c a n n o t be o b t a i n e d as a consequence of the f o r m a t i o n of lactone s t r u c t u r e s [4]. This s t u d y is a i m e d a t synthesizing a n d s t u d y i n g chemical p r o p e r t i e s of h y d r o lyzed MA1 p o l y m e r s . Mon(,mers: t)utyhncthacrylat(~ (BMA) and styrene were distilled at reduced pressure. MAI was rccrystallized from a benzene-chloroform mixtm'c. The followiog values were obtained fi)r the,m: n 2, D 1.4239 (BMA), 1.5462 (styrene) and m.p. 326°K (MAI). Mononmrs were copolylnerizcd in bulk in the presence of 0-1 wt. °/o AID under the following conditions: ] hr at 333°K and 4 hr at 388°K. Polymers from solutions in T H F or acetone were reprecipirated into cooled ethanol, dried at 353°K to constant weight. The structure of products was confirmed by results of I.R spect, roscopy, derivatography, turbidimetry mid high-fro* Vysokomol. soyed. A25: No. 9, 1934-1937, 1983. 2254

Hy(h'olyzed polymers of malcic anhydride

2255

quency acidic-basic titration. Tim following MAI p(~lymcrs w e r e obtmnod: st yrene-MAl (45.1~0-8 ut." O//o anhydride), BMA-MA1 (11.1~: 1.2 wt.°o• anhydride),. BMA-MAl-styronc (12.7-I-0.2 wt. % anhydride). Polymer molecular weights were determined by light seatt, ering "rod were 10a-3 x 10 ~. K O H ~md I-[CI were used (analyf, ically pure). I R spectra were obtained using a "Specord-751[R" spectrophotometer, derivatograms using a P a u l i k - P a u l i k - E r d e i derivatograph, model 3428. Curves of tttrbidimetrie potentiometrie and high-frequency tit, ration were obtained using NPM, pH-121, TV6L1 devices, respectively.

aT

~la0~ zoo

qOOr,K

D T A (1) and TGA (2) curves of B M A - M A - - s t y r e n e copolymers obtained while heating in air at t~ rate of 24 dog/rain. B M A - M A l - s t y r e n e hydrolyzed thermal polymer w~s obtained from its solution in 1,4-dioxane by reaction with potassium hydroxide at a temperature of 343-353°K. Reagent ratio was 1 : 2. The m i x t u r e .was k e p t at this temperature for 3 hr, then cooled to room temperature and a stoichiome~tric q u a n t i t y of hydrochloric acid added. The product was repreeipitared in water and dried in air under nmwnal conditions to constant weight. The substance is a white powder, which is readily soluble in polar solvents. Yield was 96(}o. The content of maleic acid (MA) units was: found 14.7~:0.3%, calculated 14.7%. The BMA-MA1 copolymer was saponified b y a similar method. Yield wns 97 wt. 0{~ The content o f MA units was: found 12.8:k0.2%, calculated 12.97~. Hydrolyzed styreno--MAl copolymer was obtained by a similar method. Tl~,e product was separated b y precipitation using a s a t u r a t e d solution of sodium chloride. Yield was 60%. T h e content of MA units: found 49.3+ 0.7%, calculated 49.5%. The degree of the reaction was followed in every case by the disappearance of bands of symmetrical and a n t i s y m m e t r i c vibrations of the carbonyl group of anhydride and b y the disappearance of bands due to vibrations of earboxylate ions at the stage of neutralization.

Two broad absorption bands of low and average intensity are present in IR s p e c t r a o f h y d r o l y z e d co- a n d t e r p o l y m e r s o f MA] in t h e r a n g e o f 3 6 0 0 - 3 2 0 0 era-1 w i t h m a x i m a a t 3450 a n d 3200 c m - 1 , w h i c h a r e d u e t o b o n d - s t r e t c h i n g v i b r a t i o n s o f O H g r o u p s i n v o l v e d in t h e f o r m a t i o n o f h y d r o g e n b o n d s a n d a b a n d a t 1710 em-~, r e s F o n s i b l e i b r b o n d - s t r e t e h i n g v i b r a t i o n s o f e a r b o n y l o f t h e e a r b o x y l group. All [ :oduets obtained have low heat stability. On heating a BMA-MA-styrene t e r p o l y r ' e r t o 4 3 8 ° K , t h e I R s p e c t r u m o f i t s film a g r e e s w i t h t h e s p e c t r u m of' a BMA-MAl-styrene terpolymer. Dehydration begins at temperatures of 308313°K, w h i c h i n d i c a t e s a n u n u s u a l e a s e o f s e p a r a t i o n o f w a t e r a n d e n d s a t 4 3 S ° K .

2256

V.F. MISHCHENKOet

al.

Derivatographic studies show that the process of dehydration consists of two stages (Figure). Water separation at the first stage ends at 343°K (0.4%), at the second--at 438°K (2-0%). The overall amount of water lost by the sample is close to the calculated amount: found 2.4%, calculated 2.3%. The two-stage process of dehydration may be due to different surroundings of maleic acid units in the terpolynmr

/,o,,./

//X

0

#\

OH---O

1

,¢\

Olt---O

OBu

II

At a temperature of 343°K the polymer containing structures of type I is dehydlated, while at the higher temperature of 438°K, that of type II (because of the need for hydrogen bond rupture with the participation of a BMA ester group). In accordance with the amount of water separated it may be assumed that in a BMA-MA-styene terpolymer 17 % of MA units is near styrene and the methyl group of BMA units (1) and 83%--near styrene and the ester group of BMA units (II). Results of potentiometric investigation of copolymers showed the existence of two degrees of neutralization. On the basis of curves of potentiometrie titration values of pKal and pKa2 were calculated for saponified 5fAl polymers in water. Acidity parameters of the polymers studied are tabulated. Values of pKal and pKa2 for styrene-MA copolymers given in an earlier paper [8] are 4.6 and 8-3, respectively, which points to a satisfactory correlation with the constants derived for "Styromal" in this study. It can be seen from the Table that pKal values for BMA-MA copolymers are

COI~STANTS

OF IONIZATION OF H Y D R O L Y Z E D M A L

P O L Y M E R S AND T H E I R LO%V-I~IOLECULAR

~VEIGHT A N A L O G U E S ,

298°K

Substance

pKa~

PKss

MA SA Styrene--MA BMA-MA BMA-MA-styrene VA-MA AN-MA

1"92 4-2 4"5~0'3 5"2±0'3 5"3±0"3 3'2 3'2

6"23 5'6

Note. SA i8 succinic acid, V A - v i n y l a c c t a t e a n d A ~ - a c r y l o n i t r l l e .

8"3±0"5 12"8~1"0 8"7±0"7 9"8

11"0

Results in tho literature [s] [7] This study Same [1l [E

Hydrolyzod polymers of maleie anhydride

2257

higher than pKat for a s t y r e n e - M A copolymer, which also confirms the existence of an intramolecular hydrogen bond. Practically identical first constants of ionization for BMA-MA and BMA-MAstyrene polymers prove an affinity with MA units in the terpolymer mainly of styrene and ester groups of BMA units (II). For a BMA-MA eopolymer ionization of polymers in water may be presented in the form 0Bu

/

0Bu

/

--C

--C

--i--C

N

o ".

"l-]

/

Kat

." ---*

-n+

o

o

it % o

/ --C

-C

"%0_,/,

0'

--C

%

\ o -'/-"

H

0

OBu 0

--C=O \ O \

%

/

./

0

Identical values of pKal for BMA-MA and ]3MA-MA-styrene polymers become clear from this system. A lower value of pKat for styrene-MA copolymei~ is explained by the absence of interaction of the free hydroxyl group of MA with the adjacent styrene unit. The high value of pKa2 for ]3MA-MA and AN-MA polymers may be explained by the formation of a stable hydrogen bond between the carboxyl group and the carboxylate-anion of MA units dissociated by the system mentioned. In particular, for a BMA-MA polymer the participation of carbonyl oxygen of BMA ester group in the formation of a donor-accepter bond with a carbon atom of the adjacent carboxyl group results in a redistribution of electron density in the latter, reducing acidity. This system involves isotactic arrangement of MA units in BMA-MA with an ester group of BMA units only on one side. The formation of isotactic triads of BMA-MA-iBMA is unlikely in view of steric hindrances in chain propagation in radical copolymerization of monomers. The tabulated value of pK,~2 of 8.7:L0.7 for the terpolymer is in satisfactory agreement with conclusions regarding the surroundings of MA units drawn fl'om studying thermal dehydration of ]3MA--MA-styrene. Tim presence in the terpolymer of MA units with different surroundings produces different pKa., values for MA units, whi('h are iu the vicinity of styrene units and methyl groups of BMA units (17%) and MA mills between styrene and BMA ester groups (S3'~,~,). If we assume that 17°~, of MA units have 1)Ka: values of 8.3 (as tbr st yrene-MA) and 83~/o of MA units have a pK~,, value of 12.8 (as for BMA-MA), the total aver-

2258

V. F. MISItCItEI~KOet al.

age value of pKa2 for terpolymers should be expected to be 0.83× 12.8-0.17× × 8.3~9.2. As shown by the Table, the pK~2 value calculated for terpolymers shows satisfactory agreement with the experimental value of pKa2 of 8.7=~0.7. Therefore, results of potentiometric investigations also confirm our assumptions regarding the type of surrounding of MA units in a BMA-MA-styrene terpolymer. A marked difference between pKa~ and pKa~ of the systems studied explaius the interesting special features in chemical properties of MA1 copolymers. Thus, interaction of potassium hydroxide with a BMA-MAl-styrerm terpolymer takes place according to medium polarity to form various products. In highly polar solvents, e.g. water with a 1 : 1 reagent, ratio acidic potassium salt is formed, while with a reductiou in medium polarity, e.g. on adding 1,4-dioxane, the product contains anhydride units (1775, 1840 cm- ~), as well as units of potassium salt (band in the I R spectrum at 1575 cm ~). The hydrolyzed terpolymer reacts with potassium hydroxide both in polar and in slightly polar solvents with successive neutralization of carboxyl groups ill order 9f increasing pK~ values. Acidic salts may be obtained in this case. Interaction of bis-tri-mbutylein oxide with a BMA-MAl-styrene terpolymer with a 1:2 reagent ratio results in the formation of diether units (absorption in the I R spectrum at 1627, 1638, i647 cm-1). Diether units (1627, 1638, 1647 cm -1) and maleic acid units (3350, 1710 cm -~) were detected in the polymer chain structure using a hydrolyzed terpolymer with the same ratio of reagents. q'ran~lated by E. SE~I,:R~ REFERENCES

1. K. BARAMBOIMand R. G. FOMINA In: Tr. In-ta legkoi prom-sti, No. 33, p. 126, 1967 2. J. WOLLNER, M. TIETZ and W. MEIER, U.S.A. Pat. 3682868, Publ. in R.Zh.Khim., 10C446P, 1973 3. N. G. MARINA, Yu. B. MONAKOV, S. R. RAFIKOV, I. V. DUVAKINA, O. A. PONOMAREV and Yu. I. LYSIKOV, Vysokomol. soyed. A18: 3,542, 1976 (Translated in :Polymer Sci. U.S.S.R. 18: 3, 620, 1976) 4. Khimicheskiye reaktsii polimerov, Sb. statei (Ed. by E. M. Fettes), vol. 1, p. 81, Mir, 1971 5. H. ROT, M. R~TZSCH, H. FRIDRICH an4 H. K. ROT, Act~ ]?olymerica 31: 9, 582, 1980 6. L. M. MINSK, (3. P. WANGH and W. O. KENYON, Commurlication No. 1275 fi'om the Kodak Research L~boratories 6: 2646, 1950 7. Yu. Yu. LUR'YE, Spruvochaik po analitichcskoi khimii, p. 326, Khimiya, Moscow, 1979 8. M. STEINAU, Plaste und Kautsehuk B10: 9, 517, 1963