Synthesis of peroxide-functional, butadiene-styrene emulsion copolymers

SYNTHESIS OF PEROXIDE-FUNCTIONAL, BUTADIENE-STYRENE EMULSION COPOLYMERS* V. A. ~PvcHII~, T. I. YUI~ZI-IENKO, A. I. KOZ~A_RSI~IIand ~N. N. Kv~AI~IZCA Polytoclmical Institute, Lvov

(Received 12 April 1968) MUCH attention has been given in recent years to polymers containing various functional groups in the macromolecules [1, 2], peroxides amongst them [3]. Polyfunctional copolymers make it possible to produce articles with greater heat resistance, high mechanical strength, elasticity, adhesion to metals, nonfading colour, etc. This paper describes the possibility of synthesizing a new type of peroxidefunctional copolymer based on peroxide monomers and a mixture of butadiene with styrene in aqueous emulsions. EXPERIMENTAL T h e following p e r o x i d e m o n o m e r s were e x a m i n e d for use in copolymerizations: tort. b u t y l peracrylato, H2C = C H - - C O - - O : O - C (Ctta) a (I), w i t h a n a c t i v e 02 c o n t e n t of 11-2% (11.1% theoretical); t e r t . b u t y l - 2 - a c r y l a t e - o t h y l p e r o x i d o , I - I ~ C = C I - I - - C O - - O - - ( C H 2 ) 2 - - O : : O - - C ( C H , ) a (II), 8.49% r e a c t i v e 02 c o n t e n t (8"50% theor.); d i - t - a l k o n a l k y n e peroxide, H2C=CH--C-C--C(CHs)2--O:O--C(CH2)2 (III), 8 . 7 % r e a c t i v e O2 (8"780/o thoor.); t e r t . a l k e n a l k y n o h y d r o p e r o x i d e , I-I2C = C H - - C = C - - C (CI-I2)2-- OOI-I (IV), 12.6 % r e a c t i v e o x y g e n (12.68% theor.). T h e b.p. of t h e styrene, after t h o r o u g h purification, was 35-36°C/2-3 nun, d~° 0-9067 (0.9074 according to t h e literature), n ~ 1.5458 (1.5462 according to t h e literature). T h e b u t a d i e n e was distilled twice o v e r metallic sodium. Tort. dodecyl m e r c a p t a n was used as chain r e g u l a t o r (0.1% w / w on t h e m o n o m e r m i x t u r e ) . T h e emulsifier was c e t y l t r i m e t h y l a m m o n i u m b r o m i d e , [CleH,sN(CH2)3]+Br - m a d e in Czechoslovakia (a 2O/o solution on t h e aqueous phase). T h e m o n o m e r s I and I I wore copolymerizod at p H = 3 ' 3 - 3 ' 5 in acid emulsions to e l i m i n a t e their hydrolysis; m o n o m e r s I I I a n d I V were c o p o l y m o r i z e d u n d e r t h e s a m e conditions, using a rosin soap at p H 9.8-10.3, because t h e process r a t e in acid m e d i a was v e r y s m a l l T h e h y d r o g e n ion c o n c e n t r a t i o n s of t h e latices was d e t e r m i n e d w i t h p H - m o t e r LP-58, using a glass electrode. T h e e x p e r i m e n t s wore m a d e in g r a d u a t e d ampoulos [4]; those wore p l a c e d in m e t a l containers fixed to a r o t a t i n g bar. T h e t h e r m o s t a t t e m p e r a t u r e was m a i n t a i n e d w i t h i n :E0.2°C. T h e ratio of t h e m o n o m e r m i x t u r e to t h e aqueous phase was 2 : I. T h e mol. wt. of t h e copolymers was d e t e r m i n e d b y v i s c o m e t r y [5] and t h e r e a c t i v e o x y g e n c o n t e n t in the m o n o m e r s a n d c o p o l y m e r s b y i o d o m e t r y [6].

* Vysokomol. soyed. A l l : No. 4, 789-793, 1969. 889

890

V.A.

PUCHII~ et al.

RESULTS

Peroxide-functional copolymers are widely used for the purpose of modification, they are produced mainly by oxidation [7-9 ] or by ozonization [10, 11] of existing polymers or vulcanizates [12]. The general disadvantage of the enumerated methods is the occurrence of secondary reactions during their synthesis, which result in the decomposition of the polyfunctional peroxides, degradation and structuration of the polymers, etc. Furthermore, these methods do not permit a control of the reactive centre insertion in the main chain of the macromolecule, so that the peroxide groups are irregularly distributed and are often only at the surface. TABLE l.

COPOLYMJ~RIZATI01~

OF

PERACRYLATE

MONOMERS

React. 0,, CopolyT e m p . , m o r i z a t i o n % Con• oC rate, version

Their molar ratio

Mono mers

[~], dl/g

Mol. wt.

%

i n original mixi n coture polymer

%/hr

Thermal copolymerization BD : St : I

B D : St : I I

84"3 83"3 80"3 84"3 83"3 80"3 84"3 80"3 84-3 80"3 84"3 83"3 80"3 84"3 80-3

: : : : : : : : : : : : : : :

14"7 14"7 14"7 14"7 14"7 14"7 14"7 14"7 14"7 14-7 14"7 14"7 14"7 14"7 14.7

: : : : : : : : : : : : : : :

40 40 40 50 50 50 20

1.5 1.4 1.4 3.6 3"6 3.7 1.9 1.5 3.7 3.4 6-7 6.5 6.4 16.0 14.8

20 30 30 4O 4O 4O 50 5O

43"0 42.0 41.0 48.0 47.0 50.0 44.0 34.0 48.0 44.0 45.0 50"0 45.0 48.0 44-0

1-189 0-744 0.577 0.997 0.726 0.594 1-784 1.496 1.271 1.609 2.257 2.070 1.709

121,000 I 59,500 I

41,000I 92,700I 50,200 I 42,300[ 224,000[ 171,5001 325,000 192,000] 320,0001 280,000 I 210,000 -

t

0.25 0.51 1-20 0.25 0.51 1-20 0.23 1.09 0.23 1-09 0.23 0.46 1 "09 0.23

0"53 0"78 1"39

0-33 0"65 1"50

0.11 0-15 0.24 0.21 0.27

1"09

In the presence of reducing agent B D : St : I I

84.3 : 14.7 : 1 83.3 : 14.7 : 25 80.3 : 14.7 :

A simpler polymerization

20 20 20

2.7 2.6 1.8

and more favourable of peroxide

or diene monomers,

33.0 41-4 28.0

method

monomers

of peroxide

of different

or with their mixtures.

1-547 1.500 1.217

180,5001 172,3001 125,500

group insertion

type

with

the

0.1o 0.12

0-23 0.46 1-09

o-i8

is t h e c o -

normal

vinyl

Synthesis of peroxide-functional, butadiene-styrene emulsion copolymers

891

The advantage of the above method is the greater controlling accuracy of the number of reactive centres inserted in the main chain and the possibility of locating them at different distances from the macromolecular main chain; the grafting of another t y p e of branch b y a radical mechanism can be carried out in emulsions and at milder temperature conditions, which will eliminate secondary reactions, etc. It should also be noted that the original peroxide monomers will act simultaneously, under these conditions, as monomers and as initiators [13, 14]. A free radical will form during the dissociation of the unstable peroxide bond and the monomers will act as normal generators of free radicals; their addition to the multiple C-bonds of the monomers produces the carbon-chain, peroxide-functional copolymers with reactive groups in the branches. The behavionr of the peroxide monomers during copolymerization will depend on their chemical structure and their thermal stability [15]. The results of the study are contained in Table 1; these show that a thermal emulsion copolymerization of peracrylate monomers will take place at relatively low temperatures at substantial rate. For example, the rate of monomer I copolymerization at 40°C was 1.4°/o/hr, that of I I 6.5°/o/hr. The experimental data also show that the copolymerization took place at a steady rate when the I-content in the mixture ranged from 1 to 5%, and the rate was not proportional to the square root of initiator (peracrylate) concentration. This seems to be due to a rapid increase of the chain termination rate when increasing the content of the peroxide monomer in the mixture. Table 1 thus shows that such an increase rapidly reduced the intrinsic viscosity and tool. wt. of the copolymers. The quantitative determination of the reactive oxygen content showed at the same time that the peroxidate copolymers had a larger content of reactive oxygen than the original monomer mixture. We determined the copolymerization constants b y the Alfrey method [ 16] for binary systems consisting of butadiene Jr I, and styrene q-I, which characterize the monomer activity in the copolymerization. The results of these determinations revealed the copolymerization constants of these pairs to be: rl----0-60 and ru=0-05 for the first pair, r1~-0.72 and r2----0.24 for the second pair. These constants indicate that the monomer I was the more reactive in the binary systems and that it entered more rapidly into the reaction at the beginning, thus enriching the peroxidate copolymer with reactive peroxide groups. On this basis one can assume that the first monomer in a 3-component system of butadieIm, styrene and peroxide monomer, will cause the lastnamed, being the more reactive, to copolymerize more quickly and the composition of the reactive copolymer will depend on its concentration in the mixture. Using the copolymerization constants, we calculated the integral composition of the peroxide-functional terpolymer [17] produced from a starting mixture composed of 2o/o tert.butyl acrylate, 83.3% butadiene and 14.7% styrene at 40°C at 50% conversion. The calculation showed the macromolecule to contain 32 but, adiene and 5 styrene

892

V.A.

PUOHII~ et al.

units per 1 peroxide monomer unit. This finding was confirmed also by elemental analysis and by iodometric titration of the reactive oxygen present in the copolymer. The alkenalkyne peroxide monomers have greater thermal stability a n d give a specific copolymerization in the presence of an amine emulsifier, especially the hydroperoxide monomer IV, which otherwise copelymerizes slowly under these conditions, and I I I not at all within 6 hr. Another point worth noting is that the thermal copolymerization of the 3-component mixtures without additional initiator is slow, while the presence of 0.08% w/w cumene hydroperoxide (on monomer mixture) accelerates it, obviously because of synergism. The copolymerization of peroxide monomers in the presence of redox systems w~s carried out as already described [1]; the initiators were the peroxide monomers and cumene hydroperoxide, while an iron-trilon complex ~nd Rhongalite were used as activators. The experimental results of these studies are contained in Tables 1 and 2 which show the copolymerization of these monomers to t~ke place over a redox system at room temperature, or lower temperatures, at greater rates. TABLE

2. C O P O L Y M E R I Z A T I O I ~ OF A L K E l q A L K Y N E MOI~OMERS

React. 02, % Mono inors

Their molar ratio

CopolyTemp., m o r i z a t i o n oC rate, %/hr

% Conversion

M, dl/g

Mol. wt.

in originalmixin coture polymer

Thermal copolymerization B I ) : St : I V / 84-3 : 14.7 : 83"3 : 14.7 : i 80.3 : 14-7 :

40 40 40

1.1 1.I 1.1

33-0 33.5 34.0

0-777 0.622

63,6001 45,400

0.26 0.51

-

1.23

173,70C 164,40(] I 86,40(] 193,70(] 185,20(] 138,80(] 168,800 139,706

0"26 0"50 1"18 0"26 0"50 1"18 0"26

0"43 0"49 1 "95

In the presence of reducing agent BD:St:III

BD

84.3:14.7:1 83.3 : 14.7 2 80.3 : 14.7 5 / 84.3 : 14-7 1 / 83"3 : 14.7 2 1 80.3 : 14-7 5 S t : I V / 8 4 . 3 : 14.7 1 83-3 : 14.7 : 2 80-3 : 14.7 : 5

10 10 10 20 20 20 20 20 20

6.2 6.1 6"1 12.4 11.3 10.0 11.4 4.8 1-1

43.3 42 "2 42.8 49.7 51 '3 51.0 45.5 31.4 10.2

1.508 1"454 0"953 1-621 1-576 1.301 1.451 1.307_

O.pl 1.23

0'45 0'46 0"68 0"46 0"30 0"64 0-42 0"85 1 "90

The results clearly show that the type and concentration of a peroxide monomer has a substantial influence on the reaction rate under these conditions;

Synthesis of peroxide-functional, butadiene-styrene emulsion copolymers

893

there was little effect on the rate in the case of monomers I I and I I I when increasing their concentration, b u t it slowed down on increasing the content of monomer IV in the mixture. The content of reactive oxygen remains the same in the copolymers and its content depends on the type of peroxide monomers used. The peroxide-functional butadiene-styrene copolymers were also identified b y their mol. wt. They were purified for this purpose b y precipitation with methanol from benzene solution, followed b y vacuum drying to constant weight. Their intrinsic viscosities were determined in a Bischoff-type viscometer (benzene,

25oc). The mol. wt. averages are listed Tables 1 and 2; they show that the mol. wts. of the peroxidate copolymers decreased on increasing the peroxide monomer concentration and the temperature. This happens because of the acceleration of the chain termination. The data also makes it clear that the mol. wt. of the copolymers depends on the type of peroxide monomer and on the copolymerization conditions. The results of our study thus show that different type peroxide monomers can be copolymerized with a vinyl-diene monomer mixture in emulsions to yield modified, Peroxide-functional copolymers, containing reactive groups in the macromolecular branches. Such copolymers will obviously be useful in grafting on to other types of macromolecules with different types of branch, or to produce structuration of polymers due to the decomposition of the peroxide groups and the recombination of the macro radicals; the result will be transversal bonds of a different type than those produced in a vulcanization with sulphur. CONCLUSIONS

(l) The copolymerization of peroxide monomers, such as tert.butyl peracrylate, tert.butyl-2-acrylethyl peroxide, ditert.alkenalkyne peroxides and tert.alkenalkyne hydroperoxide, with a butadiene-styrene mixture, was carried out in aqueous emulsions. (2) The copolymerization of these monomers was found to yield peroxidefunctional butadiene-styrene copolymers with reactive groups on the branches of the macromolecules. (3) These copolymer peroxidates (latices) could be used to synthesize modified copolymers in emulsions. Translated by K. A. A L L E ~ REFERENCES

1. O. B. UTVIN, Osnovy tekhnologii sinteza kauehukov (Fundamental Principles of Rubber Synthesis). Izd. "Khimiya", 1964 2. Z. M. RUMYANTSEVA, V. G. EPSHTEIN, E. G. LAZARYANTS and K. P. NOVINA, Kauehuk i rezina, No. 6, 9, 1966 3. T. P. YURZHENKO, L. S. CHUIKO, A. A. KIRICHEK and G. A. BLOKH, Kauehuk

i rezina, No. 12, 6, 1966

894

M. G. KRAKOVYA~ and S. S. SKOROKHODOV

4. Yu. I. YURZHENKO, G. N. GROMOVA and V. B. KHAITSER, Zh. obshch, khim. 16: 1505, 1946 5. A. I. SHATENSHTEIN, Yu. P. VYRSKII, N. A. PRAVIKOVA e t a / . , Prakticheskoye rukovodstvo po opredeleniyu molekulyarnykh vesov i molekulyarno-vesovogo raspredeleniya polimcrov (Practical Guide to the Determinations of Molecular Weights and their Distribution in Polymers). 1964 6. L. S. SILBERT and D. SWERN, Analyt. Chemie 30: 385, 1958 7. G. NATTA, E. BEATI a n d F. SWERINI, J. Polymer Sci. 34: 685, 1959 t

8. K. S. MINSKER, I. Z. SHAPIRO and G. A. RAZUVAYEV, Vysokomol. soyed. 4: 351, 1962 9. V. V. KORSHAK, K. K. MOZGOVA and S. P. KRUKOVSKII, Vysokomol. soyed. 5: 1625, 1963 10. N. A. PLATE, V. P. SHIBAYEV, T . I . PATRIKEYEVA and V. A. KARGIN, Vysokotool. soyed. 3: 292, 1961 11. Z. A. ROGOVIN, Polimery (Polymers). Izd. Mosk. Gos. Univ., 197, 1965 12. V. S. AL'ZITSER, V. Ye. GUL', I. A. TUTORSKII, V. A. SHERSHNEV and B, A. DOGADKIN, Vysokomol. soyed. 7: 417, 1965 13. T. I. YURZHENKO, V. A. PUCHIN and S. A. VORONOV, Dokl. Akad. Nauk SSSR 164: 1335, 1965 14. V. A. PUCHIN, T. I. YURZHENKO, S. A. VORONOV and M. S. BRITAN, Vysokomol. soyed. B9: 831, 1967 15. V. A. PUCHIN, T. I. YURZHENKO, O. Ye. BOISAN and L. M. APAROVICH, Ukrain. khim. zh. 33: 478, 1967 16. T. ALFREY, G. BORER and H. MARK, Kopolymerizatsya (Copolymerization). Izd. inostr, lit., 1953 17. T. ALFREY a n d G. GOLDFINGER, J. Chem. Phys. 14: 115, 1946

THE POLYMERIZATION OF HIGHER DIAZOALKANES* i~. G. Y ~ K O V Y A K a n d S. S. SKOROKHODOV High Polymer Institute, U.S.S.R. Acadomy of Sciences

(Received 15 April 1968) THE polymerization of aliphatic diazo compounds (diazoalkanos) is at present almost the .only method of synthesizing carbon-chain polymers with alkyl substituonts on every C-atom o f the main chain. One of the still unsolved questions of this method is the synthesis of higher polyalkylidones (from polypontylidone upwards). Numerous attempts wore made to produce them [1, 2], b u t all in vain. A n interesting point noted was that only diothyl other had boon ~sod as solvent in these experiments. T h e special structure of the alkyldiazomothano mole* Vysokomol. soyed A l l : No. 4, 794-802,

1969.