Studies in cyclic polymerization and copolymerization — XV. Synthesis and study of the cyclic polymerization of methyl-substituted divinylbenzals

408

S. G. MATSOYANand L. M. AKOPYAN"

CONCLUSION

A number of mixed polyamides have been prepared by polycondensation of the salt of p-xy]ylenediamine and sebaeic acid with amino-oenanthic and amino-undccanoic acids. The relationships between the properties and composition of the products were studied. Translated by/ E. O. PHILLIPS REFERENCES 1. S. R. RAFIKOV, B. A. ZHUBANOV, R. N. KHASANOVA, K. Z. GUMARGALIEVA and K. D. SAGINTAEVA, Vysokomol. soyed. 3: 699, 1961; S. R. RAFIKOV, B. A. ZHUBANOV, K. Z. GUMARGALIEVA, L. V. PAVLITENKO, Vysokomol. soyed. 4: 414, 1962 2. B. A. ZHUBANOV, S. R. RAFIKOV, K. Z. GUMARGALIEVA and L. V. PAVLITENKO, Vysokomol. soyed. 5: 1321, 1963 3. O. YA. FEDOTOVA, M. L. KERBER and I. P. LOSEV, Vysokomol. soyed. 3: 1528, 1961 4. F. B. GRAMER and R. G. BEAMAN', J. Polymer Sci. 21: 237, 1956

STUDIES IN CYCLIC POLYMERIZATION AND COPOLYMERIZATION - - XV. SYNTHESIS AND STUDY OF THE CYCLIC POLYMERIZATION OF METHYL-SUBSTITUTED DIVINYLBENZALS* S. G. MATSOYAI~ and L. M. AKOPYAN Institute of Organic Chemistry, Armenia S.S.R. Academy of Sciences

{Received 14 February 1962)

EARLIER, on a number of examples of the cyclic polymerization of divinylacetals, we demonstrated the possibility of forming acetal derivatives of polyvinylalcoho], e.g. polyvinylaceta]s [1-3]. The present work deals with the synthesis and study of the polymerization of aromatic divinyl acetals. Our problem was to study the effect of the quantity and position of the methyl groups on the capacity of ring-substituted divinylbenzals for cyclic polymerization and on the properties of the polymers. To this end we synthesized the following methyl-substituted aromatic divinylacetals: divinyl-(3-methyl) benzal, divinyl-(2,4-dimethyl)benzal, divinyl-(3,4-dimethyl)benzal, divinyl-(2,5-dimethyl)benzal and divinyl-(2,4,6-trimethyl)bcnzal. The properties and polymerization of divinyl(2-methyl)benzal and divinyl-(4-methyl)bcnzal have already been reported in a previous paper [3]. * Vysokomol. soyed. 5: No. 9, 1329-1333, 1963.

Studies in cyclic polymerization and copolymerization

--

XV

409

The methyl-substituted divinylbenzals were synthesized according to a previously described method of the interaction of tetra-fl-chloroethoxysilane with methyl-substituted benzaldehydes followed b y dehydrochlorination of the corresponding methyl-substituted dichlorodiethylbenzals b y means of solid caustic potassium. The physicochemieal properties and the results of the analysis of the aromatic divinylacctals obtained, are given in Table 1. The polymerization of the divinylaeetals was studied under identical conditions at 80 ° in the presence of 2 tool% azoisobutyronitrile. The radical polymerization of these monomers proceeds, like that of other aromatic divinylaeetals [3,4], according to a molecular-intramolemdar mechanism with formation of a polyvinylacetal. C H 2 = ( 2 H C H.o - - C H - I

I

O

O -9

\oH / I

c ' ' c ,H---_,H~--(J-I--CH~-I

I

O

O

\ cH

I--

,~

/

I

Ar Ar __ Ar~ 3-CH:~CsH4 ; 2,4-(CH3)2C~Ha; 2,5-(CHa)~C~H.,,; 3,4-(CHa)zC6Ha ; 2,4,6-(CHa)aC6H2• With the aim of explaining the influence of the methyl groups in the benzene ring of divinylbenzal on its capacity for cyclic polymerization, Table 2 sets out the results showing the dependence of polymer yield on polymerization time. For comparison, the same Table gives results obtained in the polymerization of divinylbenzal, divinyl-(2-methyl) benzal and divinyl-(4-methyl)benzal under similar conditions, as described previously [3]. It follows from these figures that the position and arrangement of the methyl groups in the benzene ring has a considerable effect on the polymerization reaction; the methyl substituents do not create steric obstacles to the polymerization process. Only a symmetrical arrangement of the methyl groups in the benzene ring in respect of the two vinyl groups of the monomer was found to be favourable to cyclic polymerization. For instance, the yield of polymers of divinylbenzal, divinyl-(4-methyl)benzal and divinyl-(2,4,6-trimethyl)benzal, whose molecules have a symmetry axis, is 20-26 % in the first hour of polymerization, while for unsymmetrical monomers under similar circumstances only 8-12~o polymer is formed (Table 2). Because of the asymmetric arrangement of the two methyl groups, the 3 isomeric dimethyldivinylbenzals which we studied polymerize considerably more slowly than the symmetrically arranged trimethyl-divinylbenzal; the latter can even be polymerized at room temperature in the absence of an initiator. I t is interesting to note that if the divinylacetal molecules are symmetrically arranged the molecular weight of the polymers will also be higher. I t is evident from Table 3 that although symmetrically arranged monomers polymerize more rapidly, their polymers have higher molecular weights. This appears to be due to the ease with which the chains are broken on the cyclic polymerization of asymmetrical aromatic divinyl acetals.

410

S. G . MATSOYAN a n d

-M~

O0

L . M . AKOPYAN"

O0

O0

P~

l'~ I~

1~ l"-

I~ I~,

I oo

,~

I oo

~

~

L'~ 1~

Z. P~

oo

@

I oo

I

0

p~ P~

~ %? %? %?

~

r,p

r,)

\X

411

Studies in cyclic polymerization and eopolymerization -- XV

TABLE 2. POLYMERIZATIONOF METHYL-SUBSTITUTEDDIVINYLBENZALS Ar B /oen=esl ARCH( \OCH=CH~ ~

_

~

\\~f--,~--

Yield of polymers, °/o in 1 hr . . 26.22 12.09

.

3 hr .

.

4hr .

8hr / 9hr Jl6hr . . | . . 3. .

--40.66-

41.66

24.18

--

31.92

~o.~ .~..,,

_

_

--

26hr 40hr . .

.

42.30 34.8

42.65 /

35.8

--

!

CHa

~,.~_<~_

~°~J~°~/-

-

'

S-%

CH3--~--

26"0l

--

3"3

37' 0

--

--

43".

44-04

TABLE 3. PROPERTIES OF THE POLYMEI~SOF METHYL-SUBSTITUTEDDIVINYLBENZALS Polymer Polydivinylbenzal Polydivinyl-(2 -methyl)benzal Polydivinyl-(3-methyl)benzal Polydivinyl-(4-methyl)benzal Polydivinyl-(2,4-dimethyl)benzal Polydivinyl-(2,5-dimethyl)benzal Polydivinyl-(3,4-dimethyl)benzal Polydivinyl-(2,4,6-trimethyl)ben.zal

M.p., °C

Brittle points

85-100 85-95 75-86 95-115 9,5-100 90-105 90-100 105-115

8O

68 67 66

Mol. wt. 19259 10000 11305 16800 8025 13000 8387 17300

412

•g G. MATSOYAN a n d L. M. AKOPYAI~

All the polymers of methyl-substituted divinylbenzals are powdery white substances, soluble in aromatic and chlorinated hydrocarbons. Table 3 also gives the melting point and brittle points of the product polymers. It follows from this Table that both the melting and brittle points of methyl-substituted polydivinylbenzals are virtually independent of the position and also the quantity, of methyl groups. Q

b

c 80 60

l,,

I

i

l

I

I

12'

~0

20 t

1700

I

1500

J

i

I

1700 1500 1700 FPequency , cm -t

I

1500

IR absorption spectra in the double bond valency vibration range: a--divinyl-(2,4-dimethyl)benzal; a'--polydivinyl-(2,4-dimethyl)benzal; b--divinyl(2,5-dimethyl)benzal; b'--polydivinyl-(2,5-dimethyl)benzal; c--divinyl-(2,4,6trimethyl)benzal; c'-- polydivinyl-(2,4,6-trimethyl)benzal. As was to be expected, in purified specimens of the synthesized polymers there is no residual saturation which confirms the cyclic mechanism for the polymerization reaction. As can be seen from the Figure, in the I R spectra there are practically 1635-1640 cm -1 absorption bands in the range of polymer double bonds; these are typical of the vinyl group of the corresponding monomers. The strong absorption in the range 1605-1610 cm -1 in the monomer and polymer spectra is due to the benzene ring. EXPERIMENTAl

The starting methyl-substituted benzaldehydes required for the synthesis were prepared by the methods described in the literature. 4-methylbenzaldehyde, 2,4-dimethylbenzaldehyde and 2,4,6-trimethylbenzaldehyde were prepared by the Gatterman-Koch method from toluene, m-xylene, o-xylene and mesitylene, according to [5, 6I. 2-methylbenz-

Studies in cyclic polymerization and copolymerization -- XV

413

aldehyde, 3-methylbenzaldehyde and 2,5-dimethylbenzaldehyde were synthesized according to the Somrnle reaction from (o-bromo-o-xylene, ~o-bromo-m-xylene a n d ehlororaethyl-p. xylene [7, 8]. Preparation of methyl-substituted fl,fl'-dichlorodiethylbenzal. I n t o a round bottomed flask with acounter-flow cooler were placed 0.5 tool of the uldehyde required, 173 g tetra-flchloroethoxysilane, 80.5 g anhydrous ethylenechlorohydrene and 1 ml 85~o solution of phosphoric acid. The reaction mixture was heated in a n oil bath at 100-110 ° for 10-15 hr. The reaction product was treated in 30~/o solution of caustic soda, extracted with ether, dried in anhydrous calcium chloride and, after removing the ether, distilled in a vacuum. The physieochemical properties and results of analysis of the methyl-substituted fl,fl'-diehlorodiethylbenzals obtained, are given in Table 4. TABLE 4. PHYSICOCHEMICAL PROPERTIES OF METHYL-SITBSTITUTED B, B'-DICHLORODIETHYLBENZALS

MRD Diehlorodiethylaeetal

/OCH~CH2C1 m-(CHa) C6H4CHq OCH~CH2CI

Yi:ld,

Yo

77.61

B.p.,

°C/m.m

125/1

°-o

~o

nz)

d4

-

-

-

I

-

1-33 °

Ill2 4.p.

3,4-(CH3)2C6H4CH~ OCH~CH2C1

Cl, %

78

27-40 26.96 27-72

F

68.13

154156/2

1'51751

71.70 71'55 25-83 25.61 26.05

2,4.(CHa)~C,HaCH< OCH~CH~C1 73.13 OCH~CH~C1

142143/1

1.517.~

71.64

2,5_(CH3)~C6H3CH< OCH~CH~C1 73.66 OCH2CHQC1

141/1 1-5155 1.1697 71.54 71.55 26.25 25.61

2,4,6.(CH3)aC6H~CH< OCH~CH~C OCHsCHsC }7"8

145146/2

OCHsCHsC1

139-

~.172e

71..~5

26-17 / 26.28 / 25.61 26.1,t

24.94 1.5170 1.1526 76.45 76.27 24.50 24.37

Preparation of methyl-substituted divinylbenzals. The dehydrochlorination of fl,fl'-di. ehlorodiethylbenzal was carried out in a copper reactor fitted with a copper stirrer, a drip funnel a n d a straight flow condenser, to which a receiver and water p u m p were connected. To 45 g continually stirred granulated caustic potash at 200-220 °, 0.2 reel of the required diehlorodiethylbenzal was added drop by drop in the course of 5 hr in such a way that at a residual pressure of 40 70 m m the temperature in the vapour was maintained at around 80-120 °. The distilled products were extracted in ether, dried with magnesium sulphate a n d distilled in a vacuum. The physicochemical properties, yields and elementary analysis results of the methylsubstituted divinylbenzals produced in this way are showed in Table 1. Polymerization. The synthesized monomers were polymerized in bulk in glass ampoules (in rarified nitrogen atmosphere) by azoisobutyronitrile (2 reel ~o of monomer). After polymerization had ended the polymers were separated and purified by reprecipitation from the benzal solution in petroleum ether and then they were dried in vacuum at 54 °. The molecular weight of the polymers was determined b y the ebullioscope method in benzene. The brittle

414

S. G. MATSOYAI~and L. M. AKOPYA~

temperatures were determined from the thermomeehanieal curves by studying the thermomechanical properties of the substituted polydivinylbenzals on a Tsetlin apparatus [9]. The melting points were determined by heating the polymers in a capillary tube. The I R spectra of the monomers and polymers (in a paste with vaseline oil) were taken on an IKN-12 apparatus in the range of the double bond valency vibrations by A. V. Mushegyan, to whom the authors are greatly indebted. CONCLUSIONS (1) A n u m b e r o f m e t h y l - s u b s t i t u t e d (in t h e ring) d i v i n y l b e n z a l s h a v e b e e n s y n t h e s i z e d b y d e h y d r o e h l o r i n a t i o n o f t h e c o r r e s p o n d i n g fl, fl'-dichlorodiethylbenzals. (2) T h e c a p a c i t y o f m e t h y l - s u b s t i t u t e d d i v i n y l b e n z a l s for cyclic p o l y m e r i z a t i o n in t h e p r e s e n c e o f a z o b i s i s o b u t y r o d i n i t r i l e h a s b e e n s t u d i e d in d e p e n d e n c e on t h e a m o u n t a n d position o f m e t h y l g r o u p s in t h e b e n z e n e ring. (3) I t h a s b e e n d e m o n s t r a t e d t h a t t h e m o s t f a v o u r a b l e a r r a n g e m e n t o f m e t h y l g r o u p s in t h e b e n z e n e ring is t h e s y m m e t r i c a l position a t w h i c h t h e m a x i m u m r a t e o f cyclic p o l y m e r i z a t i o n is o b s e r v e d , a n d f o r m a t i o n o f t h e highest molecular weight polymer. Translated by V. ALFORD REFERENCES 1. S. G. MATSOYAN, M. G. AVETYAN and M. G. VOSKANYAN, Vysokomol. soyed. 3: 562, 1961 2. S. G. MATSOYAN, M. G. AVETYAN, L. M. AKOPYAN, M. G. VOSKANYAN, N. M. MORLYAN and M. A. ELIAZYAN, Vysokomol. soyed. 3: 1010, 1961 3. S. G. MATSOYAN and L. M. AKOPYAN, Vysokomol. soyed. 3: 1311, 1961 4. S. G. MATSOYAN, G. M. POGOSYAN and A. A. SAAKYAN, Sb. Karbotsepnye vysokomol. soyed. (Carbo-ehain Polymers.) Izd. Akad. Nauk. SSSR, 1963 5. Sintezy org. prep. (Synthesis of Organic Preparations.) Foreign Literature Publishing House, 464, 1949 6. Roaktsii i metody issled, erg. soyed. (Reactions and Methods of Studying Organic Compounds.) Book 7, Goskhimizdat, 294, 300, 1958 7. Org. reaktsii. (Organic Reactions.) Foreign Literature Publishing House, 8, 263, 275 8. Ye. S. VASSERMAN, Ye. R. CHERTOK and Ye. Z. STERINA, Zh. prikl, khim. 23 : 869, 1950 9. B. L. TSETLIN, V. I. GAVRILOV, N. A. VELIKOVSKAYA and V. V. KOCHKIN, Zavodsk. labor. 22: 352, 1956