Polymerization of various polymers initiated by benzoyl peroxide-amine systems

Pol~u'aerlzation of various polymers

1427

12. D. Ya. TSVANKIN, Vysokomol. soyed. 6: 2078, 2083, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 11, 2304, 2310, 1964) 13. D. Ya. TSVA~NKLN,Dissertation, 1970 14. K. KOBAYASHI and T. NAGASAWA, J. Polymer Sci. C15: 163, 1966 15. K. KATAYAu~,L%,T. AM.ANO and K. NAKA)IURA, International Symposium on Macromolecular Chemistry, Preprints "vii, p. 179, Tokyo, 1966 16. D. Ya. TSVANKEq, Vysokomol. soyed. A9: 2668, 1967 17. Ya. A. ZUBOV, V. I. SELIK.~IOVA and V. A. KARGIN, Vysokomol. soyed. A9: 353, 1967 (Translated in Polymer Sci. U.S.S.R. 9: 2, 394, 1967) 18. A. PETERLIN, ft. Polymer Sci. C18: 123, 1967

POLYMERIZATION OF VARIOUS POLYMERS INITIATED BY BENZOYL PEROXIDE-AMINE SYSTEMS* ~[. F. :~IARGA_RITOVA, K. fl-.R U S A K O V A

and V. A. SNDiSHCuikOVA

.~[. V. Lomonosov Institute for Fine Chemicals Technology, BIoscow (Received 13 l%larch 1969)

THER~ is a considerable amount of work at present devoted to the polymerization of vinyl compounds under the effect of peroxide-amine initiating systems. Kinetic investigations of polymerization in the presence of binary initiators have had, as their principal aim, the discovery of methods of obtaining a high polymer yield. However, a number of specific differences between the process occurring in bulk and in emulsions should be expected to appear with initiation of this type, because of the formation of a polar complex which participates in the primary radical-formation reactions. For this purpose, we have carried out a comparative investigation of the polymerization of various monomers, the pol~nnerization being initiated by benzoyl peroxide-amine systems both in bulk and also in emulsions. EXPERIMENTAL

Benzoyl peroxide (BP), dimethylaniline (D~IA), triethylamine (TEA), aniline (.%N), methylmethacrylate (~L~CIA),styrene (St), and acrylonitrile (AoN) were purified by the usual method [1-3]. A merzolate (MK) emulsifier was used in experiments with St, and eetylpyridinechloride (CPE), purified by recrystallization from acetone and dried in vacuum, was used in the polymerization of MMA. The study of the polymerization kinetics was carried out dilatometrically in oxygen-free conditions at constant temperature. Reproducibility of the results was achieved as a preliminary in all cases. I n carrying out the emulsion polymerization, the ratio of the monomer to the aqueous phase was equal to 1 : 2 . * Vysokomol. soyed. A12: ,-k~o. 6, 1261-1267, 1970.

1 428

.~[. F. ~[.~I~G.~RITOV.~et al.

The order of the reaction with respect to the components of the initiating system, the activation energy of the process and, in certain ca~es, the latex particle size were determined. The molecular weights of the polymers obtained were determined viscometrically in benzene at 25°C. The equation [t/I-----4.68× 10-s. M °'77 [4]. was used to calculate the molecular weight of polymethylmethaerylate (PM,~L-k). RESULTS AND DISCUSSION

Polymerization initiated by the system B P - D M A . Consideration o f the results o b t a i n e d in investigations o f the p o l y m e r i z a t i o n o f v i n y l m o n o m e r s in bulk and in n e u t r a l aqueous emulsions showed t h a t the r a t e o f the reaction increases

fO

8O

Time, rain

100

FIG. 1. Polymerization of vinyl monomers in the presence of the system BP-D~IA.

[BP] = [DMA] = 0.0745 mole/1, of the organic phase: 1, 3-- St; 2, 4-- ~L'~IA; .5-- AcN; 1, 2--in bulk; 3-.5--emulsions. Temperature: 1, 3--25°C; 2, 4, 5--20°C. with increasing p o l a r i t y of the m o n o m e r in the order AcN > ~ l ~ i A > S t (Fig. 1). I t should be mentioned t h a t the p o l y m e r i z a t i o n is m ~ r k e d l y r e d u c e d in ~lkaline media ( p i t 10.3) as c o m p a r e d w i t h n e u t r a l emulsions, and Ac• does not polymerize at all. The p o l y m e r i z a t i o n of St in bulk in the presence o f the system B P - D M A has been studied previously [2]. I t was shown t h a t p o l y m e r i z a t i o n occurs at a low rate, the initial p o l y m e r i z a t i o n r a t e d e p e n d i n g on each of the c o m p o n e n t s of the initiating s y s t e m to the power 0.5. P o l y m e r i z a t i o n has been studied in t h e present work o n l y in emulsions. I t has been f o u n d t h a t the reaction r a t e is increased m a r k e d l y as c o m p a r e d with p o l y m e r i z a t i o n in bulk. W i t h a n increase in the c o n c e n t r a t i o n of the components of the initiating system, the c o m p o n e n t s being t a k e n in an equimolar ratio, the reaction r a t e increases in direct p r o p o r t i o n to the c o n c e n t r a t i o n o f the initiating system. An increase in the r a t e is also f o u n d w h e n the c o n c e n t r a t i o n of the peroxide is increased; the order o f the reaction with respect to the p e r o x i d e is equal to 0.5.

Polymerization of various polymers

1429

I-I~-,vever, with a c~nstant concentration of BP, an increc, ae in the concentration of DSL2k in the range 0.018-0.149 mole/[ of the organic phase leads to a reduction in the reaction rate, as had been found previously [5]. :-k marked fall in the molecular weight of the polystyrene is thus observed (Table 1). T.~BLE I. M O L E C U L A X IN E M U L S I O N

~VEIGIIT O F F O L Y S T Y R E N E ,

IN T H E

PRESENCE

BP-DMA

~ND

THE

OBTAINED SYSTEMS

BP-AN

Concentrations of the components of the system, mole/1, of organic phase BP 0.0745 0.0745 0.0745 BP 0.037 0-074 0-0148 0.037

OF

Mol.wt. × 10-*

D3IA 0.037

0.0745 0.15 AN 0.01 0.01 0.01 0.037

12'90 9"10 5"75 22"0 11"2 3"77 13'66

The activation energy for the emulsion polymerization of styrene in tire presence of the system B P - D ~ I A (10, 20, 30°C) is equal to 14.25 keal/mole. There has been a previous study of the polymerization of 313Lk in bulk with t'he system BP-DM_A [2]. Treatment of the results made it possible to determine the order of the reaction with respect to D3L~ (0.5) and the overall order of the reaction, which was found to be equal to unity. Since the interaction between the peroxide and amine occurs bimolecularly, the order of the reaction with respect to the peroxide will also be equal to 0.5. A similar relationship has also been found for the polymerization of 313IA in solution in benzene [6] and in bulk [7]. Polymerization of 3ISLA in emulsions in the presence of the system BP-DSIA has been studied in more detail in the present work since investigations ot this type have not been carried out previously. In determining the polymer yield as a function of the CPC concentration, the order of the reaction with respect to the emulsifier was found to be equal to unity. A directly proportional relationship between the reaction rate and the emulsifier concentration was found for M3IA during polymerization with BP at 50°C [8], and also for styrene [9]. Figure 2a shows results which indicate that, as the concentration of BP is increased to 0-5 mole/[ at a constant coneentr/~tion of D3IA, the reaction rate increases and the order of the reaction in respect to the peroxide is equal to 0.5. At higher concentrations of BP, the reaction rate was independent of the B P concentration. The molecular weight of the pol~anethylmethacrylate is inversely proportional to the square root of the B P concentration (Fig. 3).

1430

3I. F..~[tRG.'L~tTOVi et al.

The results of the emulsion polymerization of 313L-k in the presence of the system BP-I)3IA at various I)3LA concentrations are shown in Fig. 4a. It may be seen that, as the concentration of I)MA is increased up to a certain figure, the reaction rate rises but that, at high amine concentrations, the reaction rate becomes constant, as in the experiments where the ]3P concentration was varied. The molecular weight is found to fall off sharply as the I)MA concentration is increased, and the usual relationship for radical polymerization between the molecul~r weight and the square root of the initiator concentration is not found. The value of n with respect to I)MA was found to be equal to 0.56. The results of the polymerization of 313L-k at an equimolecular ratio of the components of the initiating system are shown in Fig. 5a. It may be seen that the reaction rate is proportional to the concentration of the initiating system within the range from 0 to 0.5 mole/l, that is, the overall order ot the reaction is equal to unity. As in the preceding cases, it is found ~t high concentrations of the initi~,ting system that there is a gradual reduction in the order of the re/~ction. It is known from the theory of radical polymerization that this is connected with the fact that, at high initiator concentrations, chain termination tkrough recombination of the polymeric radicals with primary radicals occurs in addition to chain termination through the meeting of polymeric radicals [9]. The activation energies for the polymerization of )L~IA in bulk (10, 20 and 30°C) and in emulsion (10, 15, 20 and 25°C) were determined with the system BP-DMA. They were found to be respectively 11.5 and 12.2 kcal/mole. It is interesting that they are the same whether the reaction occurs in bulk or in an emulsion. Polymerization of M M A in the presence of the system B P - T E A . In view of the fact that the polymerization of I ~ [ A with this system in bulk has been studied previously [3], only emulsion polymerization has been studied in detail in the present work. It was clear from a comparison of the results of the polymerization of St and MMA in bulk under the effect of B P - T E A and B P - D M A that the reaction rates increase as the polarity of the monomer is increased. The system :BP-TEA is less effective than BP-DMA. The kinetics of polymerization with the participation of B P - T E A were investigated in detail with MSIA. The data from the experiments on the polymerization of 3DIA under various conditions are shown in Fig. 2b, 4b and 5b. The polymerization rate depends on the concentration of the components of the initiating system and the emulsifier in just the same way as with BP-DSL-k as the initiating system, namely, the order with respect to B P is equal to 0.5, with respect to TEA 0.5, and with respect to the emulsifier, 1. The rate of polymerization in emulsions is considerably higher, the activation energy being the same as that found for the system BP-DMA, equal to 12.4±0.2 kcal/mole. The molecular weight of the polymers depends on the concentration of :BP and TEA to the power 0.5 (Fig. 3).

1431

Polymerization of various polymers

T h e changes in the molecular weights of the p o l y m e r s as a function of the c o n c e n t r a t i o n of the amines investigated deserve special a t t e n t i o n . T h e molecular weights of the polymers obtained with e q u i m o l a r concentrations of the corn-

1"0

m

"~ 0,3

\.4"f

0"8 ~l~

×

x

M,IO"5

r

2

b

MqO-~ 3"14

I

.! .....

!

30 ~ 0.5!/

168

0

2"0~'x

14 6 8 fO EBP]"10a,mo(e/L

12

V

114

2"8 I

t

I

I

I

I

0"05 0.1 0.15 0"20 0"25 0"3 [ BP] , mole/L

0

FIG. 2. Dependence of (1) the initial rate of polyzneMzation, (2) the molecular weight of PM~L& on the concentration of BP for a constant amine concentration: a - [D3L&] =0.074 mole/1, of the organic phase; [CPC]= t%, temperature 20°C; b--[TEAl =0.15 mole/1, of the organic phase; [CPC]=2°/o, temperature 25°C.

3

M, IO"5

40

~

2

"aO

20

10

I

0.I

I

I

"'k.

I

0"2 0.3 0"4 [BP]°'sot [~rn.~ne]o.s

I

,

0"5

Fro. 3. Dependence of the molecular weight of P.AL'~IAon the concentration of BP or amine, the concentration being raised to the power 0"5: /--dependence on [BP] o.5, system BP-D~L&; 2--dependence on [BP] 0.s, system BP-TEA; 3-- dependence on [TEA] °'s, system BP-TEA. p o n e n t s of t h e s y s t e m B P - T E A are greater, b y an order of m a g n i t u d e , t h a n t h e molecular weights of the p o l y m e r s synthesized in t h e presence of BP-D~L& (Fig. 50, b). I t has b e e n suggested t h a t amines m a y p a r t i c i p a t e in acts of chain transfer.

1432

~[. F. 5L~2GARITOV.~ et al.

B y means of 5Iayo's equation, the constants for chain transfer were found graphicall)- from the molecular weights of the polymers; these were, for st)-rene (systems BP-D3L-k) 7-8× 10-2; for ~I3[A with the s y s t e m BP-D3L4_, 1.17× 10-~-; a n d for

a

b M,IO -8

0-8 0-5'

"~-.o.4 C,'2 0

(

l

'M,lO-e q

2"0

3

~" 1.0

2

8

0"5

I

L73 0.# [OMA], moZe/L

0

~ O.l

16

0-2

I

I

I

I

I

I

0.I0 0.20 [TEA.I,mo(e/[.

O.3O

FIG. 4. Dependence of (1) the initial rate of polymerization, (2) the molecular weight of PMMA on the amine concentration at a constant concentration of BP: a--the system BP-D3L-k; [BP]----0.0T4 mole/1, of the organic phase, [ C P C ] = I ~ , temperature 20°C; b--the system BP-TEA; [BP]----0' 15 mole/1, of the organic phase, [CPC] = 2 ° k, temperature 25°C.

Wo,g//OOmZ

i ~lO-s

0-5

b

2

W,~ /IOOm[

Pl,lO-S

O.Zt 0"3

1"5

O'Z 0.1

"',~

0.1

0.2 [BP]-EDMA], mole/L

2

0.~

0.3

0

p I

I

I

I

f

r

I

O'OQ0"080"12 0"16 0"20 0"2¢ 0"28 0"32 [BP]-[TEA], mole/l.

Dependenceof (1) the initial polymerization rate; (2) the molecular weight of PSI~L4. on the concentration of the initiating system, the components having equimolar concentrations" a--the system BP-DMA; [CPC]= 1%, temperature 15°C; b--the system BP-TEA; [CPC]=2~/o, temperature 25°C. FIG. 5.

513[A w i t h the s y s t e m B P - T E A , 0.54 × 10 -3. A comparison o f these figures m a k e s it possible to confirm t h a t DM_A is the stronger chain-transfer agent. This is confirmed b y the results f r o m a s t u d y of the molecular-weight d i s t l i b u t i o n o f t h e polymer specimens. T h e m e t h o d o f fractional p r e c i p i t a t i o n was used in the case o f the

1433

. Pol~-merization of various pol)uners

s y s t e m B P - D M A . I t was f o u n d t h a t the p o l y m e r s were polydisperse, a n d t h a t t h e r e was a collection of fractions w i t h molecular weights from a few tens of thousands u p to one million. T h e p o l y m e r o b t a i n e d with t h e s y s t e m B P - T E A has a comparat i v e l y n a r r o w molecular-weight distribution (Fig. 6). This is clearly explained b y t h e fact t h a t T E A , at the c o n c e n t r a t i o n s used, is f o u n d not in the v o l u m e of the m o n o m e r b u t r a t h e r in t h e surface layers of t h e emulsifier, in c o n t r a d i s t i n c t i o n t o DSL~_, and this makes chain t r a n s f e r to the a m i n e difficult. 100- 5 2

o

1

o~

~':50 -

0 1

2.

3

pf410_ s 5

6

7

Fio. 6. (1) Integral, and (2) differential molecular-weight distribution curves for PMMA obtained in the presence of the system B P - T E A in emulsion. Temperature, 20°C: [BP]-[TEA]=0.0745 mole/1, of the organic phase. Determined by sedimentation in an ultracentrifuge. I n order to t h r o w light on a n y t o p o c h e m i c a l features characteristic of emulsion p o l y m e r i z a t i o n in t h e presence of t h e B P - a m i n e systems, m e a s u r e m e n t s were m a d e of the l a t e x particle dimensions of the P S L ~ A o b t a i n e d a t various e x t e n t s of polymerization a n d w i t h various emulsifier concentrations. The results of t h e experim e n t s , shown in Tables 2 a n d 3, m a k e it possible to state t h a t t h e same rules are T A B L E 9 D I M E N S I O N S OlV P S L ~ L % LA-

TABLE 3. D n a E ~ S I O N S

TEX

TEX

PA.RT~CLES,

PRESENCE AT

OBTAI~-ED

O F TJ~u~ S Y S T E ~ I

DIFFERENT

IN T H E

BP-TEA

COI~rERSIONS

([BP]=[TEA]-~0.037 mole/1, of the organic phase; [CPC]=2°~; temperature 20°C; pH 7.0) Conversion, % 10 30 40 50

Diameter of latex particles 830 914 1060 1160

PARTICLES

PRESENCE

OF

PMMA

OBTAINED

OF T H E

SYSTEM

L.~-

I1~" T H E

BP-TE:k

A T V A R I O U S E M U L S I F I E R CONCENT'R.A.TIONS

([BP] =[TEA] = 0"0745 mole/1, of the organic phase; pH 7.0; temperature 25°C; conversion 50%) O/ /o

Diameter oflatex particles

0.5 1.0 2.0 3.0

1404 1104 910 866

CPC,

1434

M. F. 5L~GA21TOVA et al.

obser~'ed as in ordinal- peroxide initiation [9, 10]: as the extent of pol~nnerization increases, the latex particle size rises, and as the emulsifier concentration is increased, the particle diameter decreases. Polymerization of M M A with the system B P - A N . There are indications in the literature t h a t primary and Secondary aromatic amines inhibit polymerization [11, 12]. It has been found [13] and we have found t h a t the decomposition of BP in the presence AIN occurs at a fairly high rate even at 20-25°C in solution in benzene and in emulsions containing benzene. 8

~8 "'.. 5

2 M,IO-5

-~ 0.02

~ Zl

!2

3 lO 2 1

0

°°1/

° 30

80

80

120

Time, rain FXG. 7 FIG. T. Polymerization of St nad M M A

0

8

6~02 0.0~ [SP]-[ANJ , mo{e/L

~.06

FIG. 8 in the presence of the system BB-.4~

at 25:C. [CPC]----2%. [BP]----0.074 mole/1, of the organic phase; [A~N]=0,001 mole/1. 1--St in bulk; 2--MMA in bulk; 3--SL~IA in emulsion. FIG. 8. Dependence of: /--the polymerization rate, 2--the molecular weight of P~L~L-kon the concentration of the initiating system BP-AN. [CPC]= ~~o; temperatt~re, 25°C. "When the emulsion polymerization of styrene initiated by the system B P - A N was carried out, it was found that a polymer was formed only in the presence of small quantities of AN. I t m a y be seen from Table 1 t h a t an increase in the peroxide concentration, and also in the concentration of AN, causes a marked decrease in the molecular weight of the polystyrene. It had been shown previously [2] t h a t the inhibiting action of AN is connected with its decomposition product, the so-called "black aniline". The observations made in experiments with styrene being taken into account, the investigation of- the kinetics of pol~nnerization of MMA was carried out at small concentrations of the components of the initiating system. Figure 7 shows comparative data about the polymerization of styrene and I-~LA_ in the presence of the system BP-AI~q. As when D~[A and TEA were used, in this case also the reaction rate was gTeater for ~L~IA.

Pol~nnerization of various po|~-mers

1435

For the pol~unerization of ~L~L% in emulsions in the presence of the system B P - . ~ \~, it was found that the reaction rate increased both with an increase in the concentration of aniline and also for an increase in the concentration of the peroxide. With equimolar ratios of BP and A_N, the reaction rate ~,t first increases, and then begins to fall off. The curve showing how the polymerization rate depends on the concentration of the initiating system has a maximum (Fig. 8) which is not found for systems with DMA and TEA. The results obtained in the present work make it possible to describe the overall rate of pol~unerization of St and M~'[A in the presence of the initiating systems BP-DMA and B P - T E A by the following equations: w=/c[BP] °'5. [amine] °'~ (in bulk), and w = k [ B P ] ° s.[amine]0.5.[CPC] (in emulsion). The concentration of the monomer in the latex particles is constant and is taken into account by the constant ]~ in the equations. The order of the reaction with respect to the components of the initiator could not be successfully determined in polymerization with the system B P - A N , because the products of the reaction between BP and AN have an inhibiting action on the polymerization. CONCLUSIONS

(1) The kinetics of polymerization of st~Tene and methylmethaerylate initiated by benzoyl peroxide-amine systems (triethylamine, dimethylaniline, aniline) have been studied. The order of the reaction with respect to benzoyl peroxide, and also with respect to tertiary amines (dimethylaniline and triethylamine) is equal to 0.5. When the system benzoyl peroxide-aniline is used, it has been shown that, this amine participates in initiation only" when present in small quantities, since the product of its reaction with the peroxide inhibits polymerization. (2) The activation energies for the polymerization of methylmethacrylate in bulk and in emulsions, initiated by benzoyl peroxide-amine systems, have been •calculated. It has been shown that these quantities remain constant for each system no matter whether the reaction occurs in bulk or in emulsions, although the polymerization rate in emulsions is considerably higher. (3) Molecular weights have been determined, and a study has been made o f the molecular-weight distribution of methylmethaerylate pol~uners obtained in emulsions in the presence of various initiating systems. It has been shown that, when the system benzoyl peroxide-dimethylaniline is used, dimethylaniline~participates actively in chain transfer reactions. As a result of this, the average molec•ular weights of the pol~nners are low, and the molecular weights of the individual fractions vary within a wide range. It has been found that the molecular weights depend substantially on the question whether the components of the initiating system are located in the same phase or in different phases. Translated by G. F. MODLEN

1436

K . A . A_~'DRLk_~'OVet al. REFERENCES

1. K. A. RUSA~KOVA and hl. F. 3LkRGARITOVA, Vysokomol. soyed. B9: 515, 1967 (Not traaslated in Pol}Taer Sci. U.S.S.R.) 2. ~/1.TITSYAO, Dissertation, 1958 3. M. F. 3L4~RGA.RITOVA and I. Yu. MUSA~BEKOVA, Vysokomol. soyed. 3: 530, 1961 (Translated in Polymer Sol. U.S.S.R. 3: 4, 552, 1962) 4. V. N. TSVETKOV, V. S. SKAZKA and N. M. KRAVCHENKO, Vysokomol. soyed. 2, 1045, 1960 (Translated in Polymer Sci. U.S.S.R. 3: 2, 229, 1962) 5. F. HRABAK and L. JURE~0VA, Collect. Czechoslov. chem Communic 26: 915, 1961 6. M. IMOTO, J. Chem. Soe. Japan, Industr. Chem. Sec. 58: 481, 1955 7. M. IMOTO, T. OTSU and K. KIMURA, J. Polymer Sci. 15: 475, 1955 •8. T. KRISAN, M. F. M.a~RGARITOVA and S. S. MEDVEDEV, Vysokomol. soyed. 5: 535, 1963 (Translated in Polymer Sci. U.S.S.R. 4: 5, 1207, 1963) 9. G. D. BEREZI-LNOI, P. N. KItOMINKOVSKII and S. S. MEDVEDEV, Vysokomol. soyed. 3: 1839, 1961 (Not translated in Polymer Sei. U.S.S.R.) 10. Ye. V. ZABOLOTSKAYA, N. G. SOBOLEVA, N. V. MAKLETSOVA and S. $. MEDVEDEV, I)okl. A]q SSSR 94: 81, 1954 II. K. TAKEMOTO, A. NISHIO, J. IKUBO and M. IMOTO, ~lakromolek. Chem. 42: 97, 1960 12. L. HORNER and E. SCHWENK, Liebig'sAnn. Chem. 566: 69, 1950 13. Kh. S. BAGDASA_R'YAN and P. I. MILYUTINSKAYA, Zh. fiz. khimii 34: 405, 1960

SYNTHESIS AND PROPERTIES OF COPOLYMERS OF THE POLYDIMETHYLDIPHENYLSILOXANE SERIES* K. A. A_~DRIA_~'OV, G. L. SLOR'IMSKII,V. YU. LEVL% Y r . K. GODOVSKII, I . K . KVZXETSOVA, D. Yx. TSVAXKI~, V. A. MOS~AT,EXKO and L. I. KVTEI~n~ovx Institute for Elemento-organic Compounds, U.S.S.R. Academy of Sciences (Received 14 March 1969)

T ~ . polymerization of dimethylphenylmethyl- and dimethyldiphenylcyclosilox• anes in the presence of acid or basic catalysts has been described in the literature [1,2], and it has been shown that the molecular weight of the polymers decreases to a considerable extent as the number of phenyl groups in the initial cyclosiloxanes is increased. The copolymerization of octamethyleyclotetrasiloxane (OMCTS) with octaphenylcyclotetrasiloxane (OPhCTS) under the action of K 0 H has also been described, and the kinetics of this process have been investigated [3]. There are, however, no systematic data in the literature relating to the properties of copolymers of the polydimethyldiphenylsiloxane series (PMPhS). The * Vysokomol. soyed. A12: No. 6, 1268-1276, 1970.