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Kazuo SUGIY
AMA
*
SYNOPSIS
27
The polymerization of acrylonitrile (AN) initiated by tetramethyl-2・tetrazene(TMT) and dimethyl su1fate (DMS) in dimethylformamide (DMF) was studied. The polymerization was confirmed to proceed through a radica1mechanism. The initia1rate of polymerization Rp wωexpressed by the equation: Rp
=
k[TMT] 0.52 [DMS] 0.48 [AN] 1.43. The overall activation energy for the polymerization was estimated as 10.7 kca1/mo1.In the absence of monomer，
the reaction of TMT with DMS was a1so studied kinetically by measuring the evo -lution of nitrogen. From these results and ESR measurement of the TMT/DMS system，
a possible initiation mechanism is proposed. INTRODUCTION TMT can initiate the polymerization of some vinyl monomers such as ethylene1・3)， styrene4，5)， and AN久的. The rate of polymerization of vinyl monomer initiated by TMT isaccelerated by the addition of nuc1eophilic reagents， such as acetic anhydride6)， benzyl chlo -ride7)， haloacetic acids8，9) dimethyl maleate・10)，and p-toluenesulfonic acid11) . Ithas been pointed out that the initiating species is the dimethylaminyl radical derived from the cata1ytic decomposition ofTMT. Recently， it has been found that DMS reacts with TMT to form dimethylaminyl radic，a1 tetramethylhydrazine， and molecu1ar nitrogen12). Accordingly the system of TMT and DMS could be expected to initiate the polymerization ofvinyl monomer at relatively low temperature. As expected the author has found that DMS is able to accelerate the polymerization rate of AN initiated by TMT alone. The pre:ent paper is mainly concemed with a kinetic investigation of the radica1polymeri -zation of AN in dimethylform出凶de(DMF) initiated by the system ofTMT/DMS. To elucidate the initiation mechanism
，
the reaction of TMT with DMS担theabsence of AN wasa1so studied kinetically and by ESR. Received November20，1979 本 Departmentof Industrial Chemistry， Faculty of Engineering28 近畿大学工学部研究報告Nn13 EXPERIMENTAL PARTS Materials. TMT was prepared by the oxidation of 1
，
1・dimethylhydrazinewith mercuric oxide，
as described in previous paper13).AN，methyl methacrylate (MMA)， and styrene (8t) were purified in the usual manner and redistilled in a stream of nitrogen under reduced pressure before use. Polymerization. The polymerization procedure wぉ thesame as th抗 泊 theprevious paper7). None of the polymerization were allowed to proceed beyond 15% conversion. Chemical composition of the resulting polymers were determined from their elemental analyses. The intrinsic viscosities [η] of polyacrylonitrile (P AN) were detennined in DMF at 300C by using anUbbel仙 台 viscometer. The number-average molecular weight of the P AN were calculated from ['Y1]according to the equation14 ): [η] (dl/g)= 1.75x 10-3Mn 0・66 Reaction kinetics. The kinetic apparatus consisted of a reaction vessel and an Ishii type dilatometer. The apparatus was kept isothermal t6:t0.05 in a 10 liter water bath. The amount of nitrogen fonned in the reactin of TMT and DMS was measured by a volumetric method according to Overberger et a1.1 5， 16)Isolation of reaction products.
A solution of 1 gr of DM8 in 5 ml of diethyl ether was added over a period of 50 min to a solution of 2 gr of TMT in 20 ml of diethyl ether at room temperature. After the addition was ended， the solu tion w邸 refluxedfor 2 hr. The solu tion was cooled to 50 C and 15 ml of a 10% sodium hydroxide solution wぉ added. The ether layer was taken up and dried over anhydrous
sodium sulfate. After the removal of the solvent
，
tetramethylhydrazine，
bp 71・720C(lit.17)bp 71-72) was obtained in 0.8 gr yield. The NMR spectrum showed only one peak at 2.75 ppm for two dimethylaminyl groups.
ESR measurement.
The ESR measurement was carried out with a JE8・MEinstrument(Jeol Co.) equipped
with 100-Hz modulation. The E8R spectrum was rapidly measured at room temperature by adding to a solution ofDMS in benzene.
RESULTS AND DISCUSSION Confmnation of a radical mechanism.
PolymerIZation of Acrylonitrile Initiated by the System of Tetramethyl-2・tetrazeneand Dimethyl Sulfate 29 initiated by TMT /DMS system wぉcarriedout in bulk. The results obtained are shown in Fig. 1， which verifies a radical mechanism. Fig.1 . . . . 21.0 〉 o a o t.l c 《 2 ~ 0.5 崎・ o c
。
+ω '" c .... 崎・ 0 0 2 0o
0.5 1.0 Mole fraction of MMA in feed Composition curve for the copolymerization of St and MMA by TMT / DMS system in bulk at 50oC， [TMT]=
0.02 mol/1， [DMS]=
0.01 mol/1. Kinetics of polymerization.The polymerization of AN initiated by TMT/DMS system was studied kinetically. The polymerization was carried out in DMF at varying concentration of TMT. As can be seen from Fig. 2
，
the rate of polymer包ation(Rp) is initia11y proportiona1to the 0.52 power of the con -centration of TMT. Fig.2 0.5 0.0 u') + E-0.5 cl。
-1.0 -1.5。
A、
R T‘
109[Cata]+ 3、
.
.
.
・
ー
2 0.5 u') + a E 09
Log Rp vs. log [Cata] for the polymn. of AN initiated by TMT/DMS system in DMF at 50oC，
[AN]=
4.56 mol/l. A : [TMT]=
0.02 mol/1，
[DMS] w出 variedfrom 0.00125 to 0.08 mol/1，
B : [DMS]=
0訓 mol/1，[TMT] was varied from 0.005 to 0.08 mol/1.30 近畿大学工学部研究報告 No.13 The polymerization w部 alsocarried out in DMF
，
at vary泊gconcentration of DMS and constant concentration of AN and TMT. As can be seen from Fig. 2 at concentration of DMS below about 0.01 mol/l，
Rp was proportional to the 0.48 power of the DMS concentration，
while at the concentrations of DMS higher than about 0.01 mol/l there was a sharp decrease in the rate with an increase in DMS concentration. A cause for the fall in the rate with increasing DMS concentation could be that MeSO 4・ derivedfrom DMS acts as an inhibitor or a retarder. Furthermore， the polymerization wぉ carried out in DMF at vary泊g monomer concentration and constant concentrations of TMT and DMS. 0.4 0.2 山 0.0 + a E ~ -0.2 -0.4 1.43 Rpα[AN] 0.2 0.3 0.4 0.5 0.6 0.7 109 [AN] Fig.3 Log Rp vs. log [AN] for the polymn. of AN initiated by TMT/DMS system加 DMFat 50oC，
[TMT]=
0.02 mol/1，
[DMS]=
0.01 mol/l，
[AN] was varied from 1.52 to 4.56 mol/1. As shown in Fig. 3，
the initial rate of polymerization is proportional to 1.43 power of the con -centration of AN. Therefore， the following relationship was obtained for the polymerization of AN initiated by the TMT /DMS system. Rp=
k[TMT]0.52 [DMS] 0.48 [AN] 1.43 The same kinetic behavior wぉ obtainedin the polymerization of AN initiated by the system consisting of TMT and various electrophilic reagents6・ 11) The polymerization of AN in DMF with the TMT/DMS system w鎚 carriedout抗varying。
temperatures between 35 and 55v C. The overal1activation energy of the polymer包ationof AN in DMF .initiated by the TMT/DMS was estimated as 10.7 kcal/mol from the Arrhenius plot as shown in Fig. 4. This value is nearly equal to the activation energies obtained from the poly -merization of AN initiated by the various TMT/ electrophilic reagents，
as shown in Tab. 1.31 Polymerization of Acrylonitri1e Initiated by the System of Tetramethyl-2・tetrazeneand Dimethyl Sulfate Ea= 10.7kcal/mol 0.6 0.4 0.2 凶 + a 区切 O
一
0.0 3.3 3.2 3.1 3.0 1000/T Arrhenius plot for the polymn. of AN initiated by TMT/DMS system in DMF at 35・55 0 C，[AN]=
4.56 mol/l， [TMT]=
0.02 mol/l， [DMS]=
0.01 mol/1. Fig.4 Comparison of the rate equation Rpα[TMT] X [Electrophilic R.] Y [AN] z and activation energy for the polymn. of AN initiated by the system of TMT and various electrophi1ic reagents. Table1 ESR**+
+
+
Ea* (Range) 25.4(85-1100 ) 12.6 (30・500) 11.4 (30・50 0 ) 9.4(30・500) 11.9 (60・800) 17.8 (60・80 0 ) Z 1.35 1.40 1.30 1.50 2.00 2.0。
y 0.56 0.50 0.50 0.64 0.48 x 0.59 0.58 0.59 0.62 0.57 0.60+
15.1 (50・65 0 ) 7.7 (50・71 0 ) 20.7 (30・500) 2.00 1.63 1.35 0.57 0.59 0.46 0.62 0.52 0.60+
TMT a lone Acetic anhydride Benzylch10ride bromoacetic acid Dimethyl maleate 2.4-Dinitroch1oro -benzene Co(II) ch10rideP
y
ruvic acid p-Toluene sulfonic acid DMS Additive+
*
10.7 (35・550)+
Sign shows the binary system in which the tetrame -thylhydrazine cation radical is detected. 1.43 0.48 0.52 ** Unit : kcal/mol，32 近畿大学工学部研究報告ぬ13
Molecular weight ofPAN.
The molecular weights of the resulting polymers were low
，
as shown in Fig. 5. As can be seen from Fig. 5， the reciprocal of number-average degree of polymerization depends on the square root of the concentration of TMT and DMS. The chain-transfer constant to DMF was estimated according to the equation18 ): l/Pn= Const
.
[Cata] 0.5+
CDMF([DMF]/[AN]) 4 5e
2~ グ出=k[CatalhCDMF 関F
COMF = 0.5 x 10-3 0o
0.1 0.2 0.3 0.4 0.5 [Cata] Fig.5 l/Pn vs. [cata] 0.5 in the polymn. of AN initiated by TMT/DMS system 泊DMFat 50oC，
[AN] = 4.56 mol/1. A : [TMT] = 0.02 mol/1， [DMS] wぉvaried. B : [TMT] was varied， [DMS] = 0.01 mol/1. The CDMF， which corresponds to the value of the interceptoithe Fig. 5， is found to be 0.5 x 10-3. This value agrees substantially with that found by Thomas et al.21 ， who studied the azo-initiated polymerization of AN in DMF. 2 10 8 ( x g S 6雲
4 20 40 60 Time (min) Fig. 6 Second-order plots for the reaction of TMT with DMS in DMF at various tempts. [TMT] = [DMS] = 0.025 mol/l.33
Reaction kinetics of TMT and DMS.
In order to clarify the initiation mechanism of the polymerization of AN by the TMT /DMS system， the kinetics of the reaction between TMT and DMS担DMFin the absence of AN was
made by measuring the amount of nitrogen evolved from the reaction. From the prel泊1泊arytest， the reaction rate (V) is given by Polymerization of Acrylonitrile Initiated by the System of Tetramethyl-2・tetrazeneand Dimethyl Sulfate V
=
k2[TMT] [DMS] The kinetics of"the reaction of TMT with DMS were followed at 30，
35，
40，
and 450 C. The second-order constants for the reaction were ca1culated from the following equation; k2 = (l/t) x x/a(a-x) where t is the time x is the amount ofnitrogen fonned at time t，
and a is the initial concentration of TMT and DMS. For equimolar initia1concentration of TMT and DMS， the plots of x/a(a-x) vs. t加egave good straight lines as shown in Fig. 6. The second-order rate constants (103 x:k2) were 1.84，
3.21，
5.09 and 12.6 l/mol.sec at 30，
35，
40，
and 450 C，
respectively.An Arrhenius plot of log k2 vs. I/T afforded a good straight line as shown in Fig. 7
，
which gave 19.3 kca1/mol for the energy of activation. The enthalpy of~ctivation was obtained from也eequation
L
1
H
*
"
= Ea -RT， apd the entropy of~ctivation L1
S* fromt~e
Ey巾gequ抗ion，k 2
=
kT /h exp(L
1
H
手IRT)exp(L
1
S学/R)・At30 0e
:
L
1
H*=
18.7kcal/mol
.
L
1
S九一
67.8eu. dH手 =18.7kcal/mol L 1S手 =-67.8cal/mol・deg -1.5 -2.0 -2.5 N U品 。 。 一
3.3 3.2 1000/T -3.0 3.1 Arrhenius plot for the reaction ofTMT with DMS in DMF. Detection of ESR signal. In order to obtain information about the radical species in the polymerization of AN initiated by the TMT/DMS system，
the ESR spect rum of the system was taken in benzene.34 近畿大学工学部研究報告No.13
When TMT was treated with DMS at room temperature， nitrogen was evolved， and the ESR spectrum of a radica1appeared， as shown in Fig. 8. The ESR spectrum gave the splittings for two equiva1ent nitrogents (aN = 13.6 gauss) and twelve equivalent hydrogens (aH = 12.4 gauss). Accordingly， the spectrum wぉ identified as that of thetetram~!1?-ylhydrazine radica1cation 22) which Nelsen observed in the reaction of TMT with acetic anhydride. ' ドー一--1 20 gauss Fig. 8 Esr spectrum of the tetramethylhydrazine cation radical derived from the reaction ofTMT with DMS. To further check the existence of the tetramethylhydrazine radical cation， the reaction of TMT with DMS was carried out in diethyl ether.The reaction system was followed by alkaline hydrolysis to give tetramethylhydrazine in good yield. This strongly suggested that the reaction between TMT and DMS resulted in the formation of tetramethylhydrazine cation radical.
Initiation mechanism.
From the present and previous data6・11)and from the earlier results of others12， 22)， the author proposes the scheme 1-4 for the initiation.
INITIATION MECHANISM
Me2N-N=N・NMe2
+
Me"SO 2I J V4 ， 、 今 ，h 白 し W M N q 4 ) ， dNT) M+.( N 4 3 戸 U M 、. y y ・ 且 i ・1 、 Me3NTMeS04
+
N 2 + .NMe2 2・NMe2 ~ Me2N田NMe2+ (
HNMe2+
CH2=N・Me)Me"N-NMe 2.L"-.L "'~'~'""2 +
+
Me ，.，N:MeSO ・~ Me"N-21~-1~Nle2 向M MeS04
+
Me3N Initiation Me2N・ + CH司=CH ム l CN 、 ，Polymerization of Acrylonitrile Initiated by the System of Tetramethyl-2・tetrazeneand Dimethyl Sulfate 35 The decomposition of TMT in the presence of DMS is believed to proceed through a methylation of the dimethylaminyl nitrogen of TMT with DMS12).In combination with pre -ViOUS6-11) and present results， it is confirmed the initiating species for the polymerization of AN are dimethylaminyl radica1s. On the other hand， itis considered the possibility that methyl sulfate anions react with growing polyacrylonitrile radica1to depress the propagation. REFERENCES 1) A. Good， J. C. J. Thynne， J. Chem. Soc.， B. 1967，684. 2) J. C. McGowan， L.Seed， Brit. Patent (Feb. 1959).
3) B. L.Erusa1imskii， B. L.Duntov. N. Tumarkin， Makromo1.Chem.， 66，205， (1963). 4) B.L.Erusalimskii， B. A. Dalgoplska， A. P. Kavunenko， J. Gen. Chem.， USSR， 27， 301
(1957).
5) K. Sugiyama T，'. Nakaya， M. Imoto， Makromo1.Chem.， 166，311(1973). 6) T. Nakaya， Y. Maki_， M. Imoto， ibid.， 133， 131 (1968).
7) K. Sugiyama， H. Hatanaka， T. Nakaya， M. Imoto， ibid.， 165， 163 (1973). 8) K. Sugiyama， T. Nakaya， M. Imoto， J. Polymer Sc P，.i artA-1， 9， 2689 (1971).
9) K. Sugiyama， Makromo1.Chem.， 177，691(1976).
10) K. Sugiyama， T. N aka)叫 M.Imoto， Polymer J. 2，1 (1971).
11) K. Sugiyama， J. Macromol Sci-Chem.， A13 (1)，13(1979). 12) C. J. Mich司da，D. Romans， TetrahedronLett.， 1969， 4123.
13) K. Sugiyama， T. Nakaya， M. Imoto， J.Chem. Soc. Japan， 1963，518. 14) R. C. Houtz， Text. Res. J.， 20， 786 (1950).
15) C. G. Overberger， M. T. O'Shaghnessy and H. Sha1it， J. Amer. Chem. Soc.， 71，2661(1949). 16) C. G. Overberger， M. B. Brenbaum， ibid.， 73， 2681 (1951).
17) R. T. Beltrami， E. R. Bissell， ibid.， 78，2468 (1951).
18) K. Sugiyama， T. Nakaya， M. Imoto， Polymer J. 2，709 (1971).
19) K. Sugiyama， T. Nakaya， M. Imoto， J. Macromo.1Sc A5， ，.i 1351 (1971). 20) K. Sugiyama， T. Nakaya， M. Imoto， Makromo1.Chem.， 169， 137 (1973). 21) W. M. Thomas， E. H. Gle部on，J. J. Pellon， J.Polymer Sc 1，.i 7，275 (1955). 22) S. F. Nelsen， R.B.Metzler， M. Iwamura， 91，5103 (1969).
