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Reactivity of N-vinylpyridazones in radical homo- and copolymerization
Polymer Science U.S.S.R. Vol. 28, No. 10, pp. 2435-2442, 1986 Printed in Poland
0032-3950186 $10.+ .00 ~ 1987 Pergamon Journals Ltd.
REACTIVITY OF N-VINYLPYRIDAZONES IN RADICAL HOMOAND COPOLYMERIZATION* S. A. GRIDCHIN,M. B. LACHINOV,A. V. KISIN,G. V. SHATALOV and V. P. ZUBOV Lenin Comsomol State University, Voronezh Lomonosov State University, Moscow (Receiced l2 March 1985)
A study has been made of the radical polymerization of novel vinylpyridazone monomers in chloroform with thermal and photoinitiation processes. The propagation rate constants is range over one order in the case of the studied monomers, while the bimolecular termination rate remains constant. The radical copolymerization of vinylpyridazones with styrene and MMA has been investigated and the copolymerization constants within the framework of the Q-e scheme have been determined.
N-VINYLPYRIDAZONEpolymers and copolymers are thermostable and are n o t e d for their adhesion properties and their ready colorability [1]. M o r e o v e r it is k n o w n that unsaturated derivatives o f 3-pyridazones are biologically active [2, 3] and m a y be used for the synthesis o f polymers and copolymers. However scarcely any data are available on the mechanism o f formation o f c a r b o n chain polymers with pyridazone rings in the side chains. The novel vinylpyridazone m o n o m e r s which we synthesized were 2-vinyl-3-pyridazone (I), 2-vinyl-6-phenyl-3-pyridazone (II), 2-vinyl-6-methyl-3-pyridazone (III) and 2-vinyl-6-methyl-4,5-benz-3-pyridazone (IV).
- "",,.N
C61{5
Ctt3
...."NN
:" \ N
C1t 3
-~/\/lx\
}i O I
CH-- CHa
" 0 II
CII -CH:~
.i o III
CH~CHz
Jl o IV
CH=CHe
This paper is based on a kinetic study o f the radical h o m o - and copolymerization o f these monomers. Information in [4] describes the P M R spectra o f the N-vinylpyridazones (Table 1) and it is reported that signals o f vinyl g r o u p protons o f m o n o m e r s I, II and I I I are similar, while those for IV are displaced towards a stronger field. There are two signals in the 13C N M R spectra o f the m o n o m e r s for the 13C nuclei of vinyl groups. These signals have been assigned on the basis o f the 13C m o n o r e s o n a n c e spectra. In addition, values have been obtained for the constants o f spin-spin interaction (CSSI) * Vysokomol. soyed. A28: No. 10, 2191-2197, 1986. 2435
2436
S.A. GRmCmN et aL
I:3C--,H (Table 1). On comparing the spectral parameters o f the studied c o m p o u n d s it is seen that m o s t o f these are not a function o f the nature o f substituents in the hetero-ring. There is only one feature o f note, i.e. a slight shift o f the signal for C~ in the vinyl g r o u p in IV towards a stronger field. The only CSSI that varies at all in the case o f the m o n o mers is I~3c_,a. Its minimal value likewise appears for m o n o m e r IV. A study o f the radical polymerization o f vinylpyridazones in the presence o f azobisisobutyronitrile ( A I B N ) and cyclohexylperoxydicarbonate (CPC) shows that in chloroform, dichloroethane, D M F and dioxan the reaction takes place as a h o m o p h a s e process, and soluble products are formed. The synthesized polymers also dissolve in D M S O and in aqueous solutions o f strong acids, but fail to dissolve in water, ether, or saturated hydrocarbons. The same absorption bands a p p e a r in the I R spectra o f the polymers and the m o n o m e r s (Table 1), apart f r o m bands in the 1635-1640 c m - : region relating to stretching o f > C = C < bonds in the vinyl group. This means that polymerization takes place at the expense o f double b o n d opening in the vinyl group, leaving multiple bonds in the hetero-aromatic ling intact. A similar conclusion is reached on the basis o f an analysis o f the U V spectra. In the spectra o f the m o n o m e r s there is a b a t h o c h r o m i c Hc TABLE 1. SPECTRUM PARAMETERS FOR THE VINYLPYRIDAZONES
PMR spectrs
0 0
chem. shifts for 13C, ppm
H, 6"34 6"45 6"29 5"90
C1 I 103.1] 103.3[ 102.2 100.4
II III IV
Hb
Hc
5.50 5.55 5"45 5'04
8'28 8.45 8.34 8-38
IR spectra, cm-
~3C NMR spectra
chem. shifts for ~H, J, ppm
I
Hb
N~=~/ N "~Ha
C2 130.8 129.5 130.5 128.6
CSSI Ion, Hz C1Hc [ 181"7] 181"61 180"7 179"7
C2H~ C2HI 161"1 162"8 161"1 162"9 1 6 1 " 0 162"6 160"8 162"3
C2H~ 3"9 3"9 3"9 3"8
PC=C
VCffiO
1640 1640 1640 1645
1680 1670 1670 1670
* The CSS1 for C2Ha and C2Ht do allow an alternative v.ssignment.
TABLn 2. KINETICPARAMETERSfOR POLYMERIZATIONOr N-VtNVLPYRIDAZONES (CHClz, [M]= 1 mole/L, [I] = 1 x 10 -2 mole/l, 30°C) I
VpX lOs j vi. x 10s I
Mono-
mole/l., sec
meI"
k d k , °'~ x x 10 2 vp × I0 s, (l./mole x mole/l..sec r, sec kp/kt x 106 X
0.21 0"51 0.88 1'65
8"0 5'2 7"2 5.6
kt x 10 -s P,
see) °'5
in presence of CPC I II III IV
kp
0.74 2.20 3.28 6.90
in presence of AIBN, 2 > 300 nm 0"89 1"01 1"43 2.52
[ 0"05 I 0"12 0"14 0.16
0-45 1.21 2.00 4"03
L/mole' sec 125 400 535 1200
2"8 3.3 2.7 3.0
45 95 120 160
Re,activity of N-vinylpyridazones in radical homo- and copolymerization
2437
shift (amounting to 30-40 nm) of the band for the n~z~*-transition on account of conjugation of the carbonyl group with the olefin chromophore, but this is absent from the spectra of the polymers. In the P M R spectra of the polymers there are no signals relating to vinyl protons (Table 1), though there are signals for "aliphatic" protons in a stronger field. The polymerization reactions in methanol, acetone and bznezene are heterophase processes, and the products obtained fail to dissolve in organic solvents and in some mineral acids. The latter finding may well be due to the fact that heterophase polymerization of vinyl monomers containing the pyridazone ring likewise takes place at the expense of carbon--carbon double bond opening in the ring [5], as was reported in [6] for pyridazone compounds having no alkenyl group. The polymerization rate for the studied vinylpyridazones increases regularly by practically one order on going from I to IV (see Table 2), depending on the nature of substituents in the pyridazone ring. In the homophase polymerization of vinylpyridazones in chloroform, dioxan and D M F orders of the initiation reaction and on the basis of monomer concentration were on average 0.5 _+0.03 and 1.0 +_0.1 at 30 and 60 °. It therefore appears that the polymerization rate for N-vinylpyridazones in the case of photo- and thermal initiation is described by the standard equation for radical polymerization vp = k [M] [I]÷. Initiation rates were determined for vinylpyridazone monomers. Figure 1 shows plots of induction periods versus the diphenylpicrylhydrazyl (DPPH) concentration. It is clear from the linear relations that DPPH is a strong inhibitor, and these data may therefore be used to find vl,. It is seen from Table 2 that the initiation rates for vinylpyridazones are similar, and do not account for the observed increase in the polymerization rate on going from monomer I to IV. It therefore appears that the increase in the total rate of polymerization is unrelated to change in the rate of initiation, but is due to differences in the kp/k~tvalues (Table 2). To find the absolute values of the propagation and termination constants we measured the average lifetime of propagation radicals using the rotaatiing sectormethod. The k p / k t ratios were calculated by the equation vp = kp/kt [M]/r. Plots in Fig. 2 show the propagation rates under intermittent illumination in relation to steady rates of polymerization for vinylpyridazones vs. reduced time logarithms. It is evident from Table 2 that in the case of the studied monomers there is an increase of one order in kp on going from I to IV. In the polymerization of vinylpyridazones the termination constants are close to being equal and are of the same order of magnitude as kt values for the radical polymerization of most vinyl monomers. In the same series of monomers it is seen that the degree of polymerization increases for the resultant polyvinylpyridazones (Table 2). An evaluation of the length of the kinetic chains and of P, for the polymers shows that no significant amount of chain transfer occurs in the radical homopolymerization of N-vinylpyridazones. Temperature dependence o f the polymerization rates were determined for vinylpyridazones in the interval 50-70 ° and the effective activation energy for the process Eaf=l/2Ei+Ep-1/2Eo was calculated. Next, given the known value of E1=123"3
2438
S . A . GRIDCHIN et al.
kJ/mole for AIBN [7] we determined the differences E p - 1/2Eo, which were also obtained from the data on photopolymerization o f vinylpyridazones in the interval 15-30 ° (Table 3). It was found that there is little difference in the E p - 1/2Eo values determined by different methods. In the series o f E p - l/2Eo values there is a tendency for the latter to rise on going from compound III to I. The kp values decrease in the same series o f monomers. Values o f kp and E , , proved to be a little higher for compound IV compared with I-III. It should be noted that in the series of single-type monomers there is a fairly marked dependence of both kp and E p - 1/2Eo on the nature of the hetero-aromatic substituent. To investigate the relative reactivities of the novel monomers and to determine the properties o f the copolymers, having pyridazone rings in the side chain, a study was made o f the copolymerization of vinylpyridazones with M M A and styrene, monomers differing as to the character o f polarization o f the double bond.
Vrs/vst 0'7 _ ~ ' ,
60 06o
4
12 [DPPH], 10~ molell.
20
0"5-
0~
I
1
FIG. 1
I
2
I
3 log t.~s,
FIG. 2
FIG. 1. Induction period in polymerization of monomers I-IV vs. DPPH concentration; [M]=I, [CPC] = 1 x 10- ~ mole/L; 30°. FIG. 2. Ratio of polymerization rate for vinylpyridazones I-IV under intermittent illumination to the stationary rate vs. logarithm of reduced time; [M] = 1, [AIBN] = 1 x 10- 2 mole/L; 30°.
TABLE 3. ACTIVATION ENERGIES -~eff AND Ep-1/2~'o VALUES FOR POLYMERIZATION OF N-VINYLPYRIDAZONES (k J / m o l e )
Monomer I II III IV
E,. [ G - t/2 Eo with thermoinitiation 78"4_+0"2 16"7+ 0"2 77"5_+0'1 15-9+ 0-1 77.14-0.1 15.54-0"1 79'0 _+0.3 17"34-0.3
I
Ep- 1/2 Eo
I with photoinitiation 16'3 + 0"1 16.0_+0"1 15.84-0.2 16-6_+0.2
Reactivity of N - v i n y l p y r i d a z o n e s in radical homo- and copolymerization
2439
TABLE 4. CONSTANTS AND PARAMETERS FOR COPOLYMERIZATION OF VINYLPYRIDAZONES WITH M M A
(Q2=0"78, e2=0-4) and with styrene (Q2 = 1-0, e 2 = - 0 - 8 ) ([Ms] + [M2] = 1 mole[L; CHCI3, 60°; [AIBN] = 1 x 10- 2 mole/L)
M2
Ma
rl
MMA Styrene MMA Styrene MMA Styrene MMA Styrene
I
II III IV
r2
1 "56 0'43 0"49 1 "45 0'30 1 "20 0"27 0"24
I rl"r2
0"63 0"53 0"58 0-51 i 0'55 0'90 1"65
0-70
0"98 0'23 0"28 0"74 0"16 1 "08 0"45 0'17
lira
l/r2
Q,
e~
0"64 2"32 2'04 0'69 3"33 0"83 3"70 4"17
1 "59 1 "89 1 "72 1 '96 1"82
1'18 0"71 0"86 1 '26 0"82 1"04 0"68 0"49
0"26 0'23 -0"71 - 0"25 -0"93 -0"51 1 "30 0'54
1'11 0"61 1"43
F i g u r e 3 shows the c o m p o s i t i o n o f c o p o l y m e r s o f v i n y l p y r i d a z o n e s w i t h M M A and styrene in r e l a t i o n to t h a t o f the m o n o m e r pairs. U s i n g the e x p e r i m e n t a l d a t a we then calculated c o p o l y m e r i z a t i o n c o n s t a n t s r l a n d rz as well as p a r a m e t e r s Q a n d e (Table4). A n analysis o f the r l a n d r 2 values shows t h a t c o p o l y m e r i z a t i o n r e a c t i o n s o f m o n o m e r s I with M M A , a n d m o n o m e r s I I with styrene are close to ideal processes: p r o d u c t s o f the c o p o l y m e r i z a t i o n c o n s t a n t s are respectively 0.98 a n d 1.08 (Table 4). The d i s t r i b u tion o f units in the chains has a statistical character.
rnt, mole fpacEon I.OCL
0.2 ~ 02
b
I
J
06
1.0
~v
[ .0.2
I I 0.8 10 /'17, mole £pach'on
F1o. 3. Composition of copolymers m~ of vinylpyridazone monomers M t with MMA (a) and styrene (b) vs. composition of monomer mixture; [M~]+ [M2]= 1, [AIBN]= 1 × 10 -2 mole/L; 60 °.
A n a l t e r n a t i o n t e n d e n c y was o b s e r v e d for m o n o m e r s I I a n d I I I w i t h M M A , a n d f o r I a n d I V w i t h styrene. F o r these p a i r s o f m o n o m e r s there are a z e o t r o p i c mixtures, the c o -
p o l y m e r c o m p o s i t i o n being equal to t h a t o f the m o n o m e r m i x t u r e (Fig. 3). C o p o l y m e r i z a t i o n o f m o n o m e r s I w i t h M M A , a n d m o n o m e r s I I a n d I I I w i t h styrene results in enr i c h m e n t o f the c o p o l y m e r s with d i a z i n e units. I n the c o p o l y m e r i z a t i o n o f I V with M M A p o l y m e r s a r e i m p o v e r i s h e d in diazine units ,irrespective o f the m o n o m e r ratio.
2440
S.A. GRIDCHINet al.
Q values for the vinylpyridazones are typical for monomers containing conjugated bonds. As regards reactivity monomers I, II and III approximate to styrene. It is characteristic that there is a relationship between Q and kp values in accordance with ideal reactivity concepts. However, it should be noted that e values differ for monomers I and IV. It was to be expected that the vinylpyridazones would possess electron donor properties, i.e. that e < 0 would be typical for these monomers. However, this is actually the case for compounds II and III only: for I and IV we have e > 0 , which must mean t h a t a change in the characterization of polarization of the double bond is involved.
In l/pz-I.n Q1
FIG. 4. Reduced values ol l/r2 v s , el for copolymerization of vinylpyridazones with MMA (1) and styrene (2) within framework of the Q - e scheme.
Semilogarithmic dependences of 1It 2 o n el during copolymerization of vinylpyridazones with M M A (1) and styrene (2) are illustrated in Fig. 4 on the basis of a Q - e scheme. The variation in the angle of slope of curves 1 and 2 in Fig. 4 is due to the dissimilarity o f polarization o f the double bonds o f M M A and styrene. The relations obtained do raise the problem of how kinetic parameters are related to the structure o f the monomers. Signals of vinyl group protons of monomer IV are displaced towards stronger field compared with signals of the same protons in compounds I-III (Table 1). This means that monomer IV is less active compared with the other monomers in the pyridazone series, but the radical appertaining to IV is more active, as is borne out by values of kp and Q calculated from data on the homo- and copolymerization of vinylpyridazones presented in Tables 2 and 4. As was noted above, changes occuring in chemical shifts for 13C nuclei in the N M R spectra are only slight, as the induction effect of substituents in the hetero ring is largely attenuated on account of remoteness of the vinyl group from carbon atoms. The slight displacement of the signal of C~ in monomer IV towards a stronger field and the minimal value of CSSI for this monomer are the only grounds one has for assuming that electronegativity is lowest for the hetero aromatic substituent in compound IV, which accounts for this monomer having the highest value of e among all the vinylpyridazones under review. However, it must be said that the ~3C N M R data do not provide any clear resolution of problem of why electron
Reactivity of N-vinylpyridazonos in radical homo- and copolymerizatiou density on
>C=C<
2441
o f the vinyl g r o u p is lower f o r the studied v i n y l p y r i d a z o n e s .
F u r t h e r investigations will have to be u n d e r t a k e n to find reasons f o r the u n e x p e c t e d c h a n g e in the m a n n e r o f p o l a r i z a t i o n o f the d o u b l e bond. The kinetics of the homo- and the copolymerization were investigated by a dilatometric method in CHCI3 solution. The reaction system was degassed in a vacuum apparatus with repeated freezing in liquid nitrogen to a residual pressure of 10_ 3 GPa. The initiators (AIBN and CPC) and the inhibitor (DPPI-/) were used in the form of freshly prepared solutions. The homo- and copolymerization products were separated from Chloroform, dioxan and D M F by precipitation with diethyl ether, after which further purification was carried out by reprecipitation. Lifetimes of the propagation radicals were determined by the rotating sector method [8]. Polymerization was initiated by UV-irradiation at 30", using a DRSh-250 lamp (2 > 300 nm) The IR spectra of the monomers, homo- and copolymers were recorded (CaBr disks or films) on the ISK-29 or UR-20 equipment, and the PMR spectra on the Tesla spectrometer (80 MHz) or. the Perkin-Elmer instrument (60 MHz) in CC14, CDCI3 or trifluoroacetic acid (monomers at 20 and 60 ° and polymers at 50° using hexamethyldisiloxane as the internal standard). The 13C N M R spectra were recorded on the Bruker equipment (20 MHz) in DMSO-d6. Density values were obtained for the monomers and polymers by pycnometry in chloroform at 20 + 0"1° using the formula p = Po + (1 -Po/Px) × c [9], where p is the density of the solution (polymer •or monomer) g/ml. Contraction coefficients Ko were calculated by the equation Kc= l / p , , - 1 / p p o where p~ and pp are densities of the monomer and polymer (Table 5). TABLE 5. COEFFICIENTSOF CONTRACTIONFOR THE VINYLPYRIDAZONES (CHCI3 used as the solvent, 20 °) Compounds
Density, g/cm 2
monomer
polymer
1
1.177
1I 1II IV
1.123 1'065
1.407 1.390 1-381 1.367
1.102
KK, cm3/g 0"14 0.1") 0.21 0-18
Molecular weights of the monomers were determined by cryoscopy in dioxan or benzene, or by mass spectrometry using the Varian MAT-311 model; number-average molecular weights of the polymers were obtained with the aid of the EP-75 ebulliograph in chloroform. The composition of copolymers of vinylpyridazones with MMA and styrene were determined by spectrophotometric analysis (Specord UV-VIS equipment) in chloroform, using absorption bands, in the UV short-range portion of the spectrum, typical for vinylpyridazones. Copolymer compositions were verified in line with the results of elemental analyses. Copolymerization constants rl and r2 were calculated by an analytical method using the ES-1022 computer [10]. Trahslated by R. J. A. HENDRY
REFERENCES 1. Pat. Japan, 5124388-publ. in RefZhKhim, PS292P, 1977 2. G. V. SHATALOV, S. A. GRIDCHIN and B, I. MIKHANT'EV, In: Vsesoyuz. simpoz, po tselenapravlennomu izyskaniyu novykh fiziologicheski aktivnykh veshchestv (All-Union Syrup. on Search for Novel Physiologically Active Substances). p. 52, Zinatne, Riga, 1979
2442
P.V.
ZHIRKOV
3. S. A. GRIDCHIN, G. V. SHATALOV and B. I. MIKHANT'EV, In: Tez. dokl. Vseoyuz. konf. "Sintez i mekhanizm deistviya fiziologicheski aktivnykh veshchestv" (Abstracts of Reports of All-Union Conf. on the Synthesis and Mechanism of Action of Physiologically Active Substances), p. 109, Odessa Univ. Press, Odessa 1976 4. G. V. SHATALOV, B. I. MIKHANT'EV and S. A. GRIDCHIN, Khimiya heterotsikl, soyed., 3, 394, 1980 5. Y, MATSUBARA, K. KIYOJI, M. YOSHIHARA and T, MAESHIMA, J. Chem. Soc. Japan. Chem. and Ind. Chem., 10, 1992, 1973 6. Y, MATSUBARA, M. NOGUCHI, M. YOSHIHARA and T. MAESHIMA, Chem. Letters, 6, 601, 1973 7. D. OUDIAN, Osnovy khimii polimerov (Principles of Polymer Chemistry), Mir, Moscow, 223, 1974 8. G. P. GLADYSHEV and V. A. POPOV, Radikal'naya polimerizatsiya pri glubokikh atepenyakh prevrashcheniya (Radical Polymerization with High Degrees of Conversion). ~,Iauka, Moscow, 174, 1974 9. H. HOPFF and M. LUPPAX, Makromolek. Chem. 66: 157, 1963 I0. A. I. YEZRIELEV, E. L. BROKHINA and Ye. S. ROSKIN, Vysokomol. soyed. A l l : 8, 1670, 1969 (Translated in Polymer Sci. U.S.S.R. 11: 8, 1894, 1969)
Polymer Science U.S.S.R.
Vol. 28, No. 10. pp. 2442-2448, 1986
Printedin Poland
0032-3950/86 $10.00 + .00 © 1987PergamonJournalsLtd.
MOLECULAR M A S S DISTRIBUTION IN ISOTHERMAL RADICAL POLYMERIZATION IN A CASCADE OF IDEAL MIXING REACTORS* P. V. ZHIRKOV Institute of Chemical Physics Section, U.S.S.R. Academy of Sciences
(Received 12 March 1985) The macrokinetics of initiated radical polymerization in a cascade of ideal mixing continuous reactors is described. The degree of polymerization and the MMD range are analyzed as a function of the effective polymerization and initiation constants and of the reaction mixture feed rate. It is shown that within the technological region of change of the parameters the degree of polymerization is decreased along the cascade steps. A non-steady change in the degree of polymerization and in the MMD range with change in reagent consumption is observed. A LARGE n u m b e r o f polymers are o b t a i n e d in i n d u s t r y in cascade mixing reactors (e.g. low pressure polyethylene, polystyrene, etc.). Several pieces o f e q u i p m e n t are c o m b i n e d in sequence in a single p r o d u c t i o n chain, in each of which the reaction mixture is h o m o * Vysokomol. soyed. A28: No. 10, 2198-2203, 1986.
0032-3950186 $10.+ .00 ~ 1987 Pergamon Journals Ltd.
REACTIVITY OF N-VINYLPYRIDAZONES IN RADICAL HOMOAND COPOLYMERIZATION* S. A. GRIDCHIN,M. B. LACHINOV,A. V. KISIN,G. V. SHATALOV and V. P. ZUBOV Lenin Comsomol State University, Voronezh Lomonosov State University, Moscow (Receiced l2 March 1985)
A study has been made of the radical polymerization of novel vinylpyridazone monomers in chloroform with thermal and photoinitiation processes. The propagation rate constants is range over one order in the case of the studied monomers, while the bimolecular termination rate remains constant. The radical copolymerization of vinylpyridazones with styrene and MMA has been investigated and the copolymerization constants within the framework of the Q-e scheme have been determined.
N-VINYLPYRIDAZONEpolymers and copolymers are thermostable and are n o t e d for their adhesion properties and their ready colorability [1]. M o r e o v e r it is k n o w n that unsaturated derivatives o f 3-pyridazones are biologically active [2, 3] and m a y be used for the synthesis o f polymers and copolymers. However scarcely any data are available on the mechanism o f formation o f c a r b o n chain polymers with pyridazone rings in the side chains. The novel vinylpyridazone m o n o m e r s which we synthesized were 2-vinyl-3-pyridazone (I), 2-vinyl-6-phenyl-3-pyridazone (II), 2-vinyl-6-methyl-3-pyridazone (III) and 2-vinyl-6-methyl-4,5-benz-3-pyridazone (IV).
- "",,.N
C61{5
Ctt3
...."NN
:" \ N
C1t 3
-~/\/lx\
}i O I
CH-- CHa
" 0 II
CII -CH:~
.i o III
CH~CHz
Jl o IV
CH=CHe
This paper is based on a kinetic study o f the radical h o m o - and copolymerization o f these monomers. Information in [4] describes the P M R spectra o f the N-vinylpyridazones (Table 1) and it is reported that signals o f vinyl g r o u p protons o f m o n o m e r s I, II and I I I are similar, while those for IV are displaced towards a stronger field. There are two signals in the 13C N M R spectra o f the m o n o m e r s for the 13C nuclei of vinyl groups. These signals have been assigned on the basis o f the 13C m o n o r e s o n a n c e spectra. In addition, values have been obtained for the constants o f spin-spin interaction (CSSI) * Vysokomol. soyed. A28: No. 10, 2191-2197, 1986. 2435
2436
S.A. GRmCmN et aL
I:3C--,H (Table 1). On comparing the spectral parameters o f the studied c o m p o u n d s it is seen that m o s t o f these are not a function o f the nature o f substituents in the hetero-ring. There is only one feature o f note, i.e. a slight shift o f the signal for C~ in the vinyl g r o u p in IV towards a stronger field. The only CSSI that varies at all in the case o f the m o n o mers is I~3c_,a. Its minimal value likewise appears for m o n o m e r IV. A study o f the radical polymerization o f vinylpyridazones in the presence o f azobisisobutyronitrile ( A I B N ) and cyclohexylperoxydicarbonate (CPC) shows that in chloroform, dichloroethane, D M F and dioxan the reaction takes place as a h o m o p h a s e process, and soluble products are formed. The synthesized polymers also dissolve in D M S O and in aqueous solutions o f strong acids, but fail to dissolve in water, ether, or saturated hydrocarbons. The same absorption bands a p p e a r in the I R spectra o f the polymers and the m o n o m e r s (Table 1), apart f r o m bands in the 1635-1640 c m - : region relating to stretching o f > C = C < bonds in the vinyl group. This means that polymerization takes place at the expense o f double b o n d opening in the vinyl group, leaving multiple bonds in the hetero-aromatic ling intact. A similar conclusion is reached on the basis o f an analysis o f the U V spectra. In the spectra o f the m o n o m e r s there is a b a t h o c h r o m i c Hc TABLE 1. SPECTRUM PARAMETERS FOR THE VINYLPYRIDAZONES
PMR spectrs
0 0
chem. shifts for 13C, ppm
H, 6"34 6"45 6"29 5"90
C1 I 103.1] 103.3[ 102.2 100.4
II III IV
Hb
Hc
5.50 5.55 5"45 5'04
8'28 8.45 8.34 8-38
IR spectra, cm-
~3C NMR spectra
chem. shifts for ~H, J, ppm
I
Hb
N~=~/ N "~Ha
C2 130.8 129.5 130.5 128.6
CSSI Ion, Hz C1Hc [ 181"7] 181"61 180"7 179"7
C2H~ C2HI 161"1 162"8 161"1 162"9 1 6 1 " 0 162"6 160"8 162"3
C2H~ 3"9 3"9 3"9 3"8
PC=C
VCffiO
1640 1640 1640 1645
1680 1670 1670 1670
* The CSS1 for C2Ha and C2Ht do allow an alternative v.ssignment.
TABLn 2. KINETICPARAMETERSfOR POLYMERIZATIONOr N-VtNVLPYRIDAZONES (CHClz, [M]= 1 mole/L, [I] = 1 x 10 -2 mole/l, 30°C) I
VpX lOs j vi. x 10s I
Mono-
mole/l., sec
meI"
k d k , °'~ x x 10 2 vp × I0 s, (l./mole x mole/l..sec r, sec kp/kt x 106 X
0.21 0"51 0.88 1'65
8"0 5'2 7"2 5.6
kt x 10 -s P,
see) °'5
in presence of CPC I II III IV
kp
0.74 2.20 3.28 6.90
in presence of AIBN, 2 > 300 nm 0"89 1"01 1"43 2.52
[ 0"05 I 0"12 0"14 0.16
0-45 1.21 2.00 4"03
L/mole' sec 125 400 535 1200
2"8 3.3 2.7 3.0
45 95 120 160
Re,activity of N-vinylpyridazones in radical homo- and copolymerization
2437
shift (amounting to 30-40 nm) of the band for the n~z~*-transition on account of conjugation of the carbonyl group with the olefin chromophore, but this is absent from the spectra of the polymers. In the P M R spectra of the polymers there are no signals relating to vinyl protons (Table 1), though there are signals for "aliphatic" protons in a stronger field. The polymerization reactions in methanol, acetone and bznezene are heterophase processes, and the products obtained fail to dissolve in organic solvents and in some mineral acids. The latter finding may well be due to the fact that heterophase polymerization of vinyl monomers containing the pyridazone ring likewise takes place at the expense of carbon--carbon double bond opening in the ring [5], as was reported in [6] for pyridazone compounds having no alkenyl group. The polymerization rate for the studied vinylpyridazones increases regularly by practically one order on going from I to IV (see Table 2), depending on the nature of substituents in the pyridazone ring. In the homophase polymerization of vinylpyridazones in chloroform, dioxan and D M F orders of the initiation reaction and on the basis of monomer concentration were on average 0.5 _+0.03 and 1.0 +_0.1 at 30 and 60 °. It therefore appears that the polymerization rate for N-vinylpyridazones in the case of photo- and thermal initiation is described by the standard equation for radical polymerization vp = k [M] [I]÷. Initiation rates were determined for vinylpyridazone monomers. Figure 1 shows plots of induction periods versus the diphenylpicrylhydrazyl (DPPH) concentration. It is clear from the linear relations that DPPH is a strong inhibitor, and these data may therefore be used to find vl,. It is seen from Table 2 that the initiation rates for vinylpyridazones are similar, and do not account for the observed increase in the polymerization rate on going from monomer I to IV. It therefore appears that the increase in the total rate of polymerization is unrelated to change in the rate of initiation, but is due to differences in the kp/k~tvalues (Table 2). To find the absolute values of the propagation and termination constants we measured the average lifetime of propagation radicals using the rotaatiing sectormethod. The k p / k t ratios were calculated by the equation vp = kp/kt [M]/r. Plots in Fig. 2 show the propagation rates under intermittent illumination in relation to steady rates of polymerization for vinylpyridazones vs. reduced time logarithms. It is evident from Table 2 that in the case of the studied monomers there is an increase of one order in kp on going from I to IV. In the polymerization of vinylpyridazones the termination constants are close to being equal and are of the same order of magnitude as kt values for the radical polymerization of most vinyl monomers. In the same series of monomers it is seen that the degree of polymerization increases for the resultant polyvinylpyridazones (Table 2). An evaluation of the length of the kinetic chains and of P, for the polymers shows that no significant amount of chain transfer occurs in the radical homopolymerization of N-vinylpyridazones. Temperature dependence o f the polymerization rates were determined for vinylpyridazones in the interval 50-70 ° and the effective activation energy for the process Eaf=l/2Ei+Ep-1/2Eo was calculated. Next, given the known value of E1=123"3
2438
S . A . GRIDCHIN et al.
kJ/mole for AIBN [7] we determined the differences E p - 1/2Eo, which were also obtained from the data on photopolymerization o f vinylpyridazones in the interval 15-30 ° (Table 3). It was found that there is little difference in the E p - 1/2Eo values determined by different methods. In the series o f E p - l/2Eo values there is a tendency for the latter to rise on going from compound III to I. The kp values decrease in the same series o f monomers. Values o f kp and E , , proved to be a little higher for compound IV compared with I-III. It should be noted that in the series of single-type monomers there is a fairly marked dependence of both kp and E p - 1/2Eo on the nature of the hetero-aromatic substituent. To investigate the relative reactivities of the novel monomers and to determine the properties o f the copolymers, having pyridazone rings in the side chain, a study was made o f the copolymerization of vinylpyridazones with M M A and styrene, monomers differing as to the character o f polarization o f the double bond.
Vrs/vst 0'7 _ ~ ' ,
60 06o
4
12 [DPPH], 10~ molell.
20
0"5-
0~
I
1
FIG. 1
I
2
I
3 log t.~s,
FIG. 2
FIG. 1. Induction period in polymerization of monomers I-IV vs. DPPH concentration; [M]=I, [CPC] = 1 x 10- ~ mole/L; 30°. FIG. 2. Ratio of polymerization rate for vinylpyridazones I-IV under intermittent illumination to the stationary rate vs. logarithm of reduced time; [M] = 1, [AIBN] = 1 x 10- 2 mole/L; 30°.
TABLE 3. ACTIVATION ENERGIES -~eff AND Ep-1/2~'o VALUES FOR POLYMERIZATION OF N-VINYLPYRIDAZONES (k J / m o l e )
Monomer I II III IV
E,. [ G - t/2 Eo with thermoinitiation 78"4_+0"2 16"7+ 0"2 77"5_+0'1 15-9+ 0-1 77.14-0.1 15.54-0"1 79'0 _+0.3 17"34-0.3
I
Ep- 1/2 Eo
I with photoinitiation 16'3 + 0"1 16.0_+0"1 15.84-0.2 16-6_+0.2
Reactivity of N - v i n y l p y r i d a z o n e s in radical homo- and copolymerization
2439
TABLE 4. CONSTANTS AND PARAMETERS FOR COPOLYMERIZATION OF VINYLPYRIDAZONES WITH M M A
(Q2=0"78, e2=0-4) and with styrene (Q2 = 1-0, e 2 = - 0 - 8 ) ([Ms] + [M2] = 1 mole[L; CHCI3, 60°; [AIBN] = 1 x 10- 2 mole/L)
M2
Ma
rl
MMA Styrene MMA Styrene MMA Styrene MMA Styrene
I
II III IV
r2
1 "56 0'43 0"49 1 "45 0'30 1 "20 0"27 0"24
I rl"r2
0"63 0"53 0"58 0-51 i 0'55 0'90 1"65
0-70
0"98 0'23 0"28 0"74 0"16 1 "08 0"45 0'17
lira
l/r2
Q,
e~
0"64 2"32 2'04 0'69 3"33 0"83 3"70 4"17
1 "59 1 "89 1 "72 1 '96 1"82
1'18 0"71 0"86 1 '26 0"82 1"04 0"68 0"49
0"26 0'23 -0"71 - 0"25 -0"93 -0"51 1 "30 0'54
1'11 0"61 1"43
F i g u r e 3 shows the c o m p o s i t i o n o f c o p o l y m e r s o f v i n y l p y r i d a z o n e s w i t h M M A and styrene in r e l a t i o n to t h a t o f the m o n o m e r pairs. U s i n g the e x p e r i m e n t a l d a t a we then calculated c o p o l y m e r i z a t i o n c o n s t a n t s r l a n d rz as well as p a r a m e t e r s Q a n d e (Table4). A n analysis o f the r l a n d r 2 values shows t h a t c o p o l y m e r i z a t i o n r e a c t i o n s o f m o n o m e r s I with M M A , a n d m o n o m e r s I I with styrene are close to ideal processes: p r o d u c t s o f the c o p o l y m e r i z a t i o n c o n s t a n t s are respectively 0.98 a n d 1.08 (Table 4). The d i s t r i b u tion o f units in the chains has a statistical character.
rnt, mole fpacEon I.OCL
0.2 ~ 02
b
I
J
06
1.0
~v
[ .0.2
I I 0.8 10 /'17, mole £pach'on
F1o. 3. Composition of copolymers m~ of vinylpyridazone monomers M t with MMA (a) and styrene (b) vs. composition of monomer mixture; [M~]+ [M2]= 1, [AIBN]= 1 × 10 -2 mole/L; 60 °.
A n a l t e r n a t i o n t e n d e n c y was o b s e r v e d for m o n o m e r s I I a n d I I I w i t h M M A , a n d f o r I a n d I V w i t h styrene. F o r these p a i r s o f m o n o m e r s there are a z e o t r o p i c mixtures, the c o -
p o l y m e r c o m p o s i t i o n being equal to t h a t o f the m o n o m e r m i x t u r e (Fig. 3). C o p o l y m e r i z a t i o n o f m o n o m e r s I w i t h M M A , a n d m o n o m e r s I I a n d I I I w i t h styrene results in enr i c h m e n t o f the c o p o l y m e r s with d i a z i n e units. I n the c o p o l y m e r i z a t i o n o f I V with M M A p o l y m e r s a r e i m p o v e r i s h e d in diazine units ,irrespective o f the m o n o m e r ratio.
2440
S.A. GRIDCHINet al.
Q values for the vinylpyridazones are typical for monomers containing conjugated bonds. As regards reactivity monomers I, II and III approximate to styrene. It is characteristic that there is a relationship between Q and kp values in accordance with ideal reactivity concepts. However, it should be noted that e values differ for monomers I and IV. It was to be expected that the vinylpyridazones would possess electron donor properties, i.e. that e < 0 would be typical for these monomers. However, this is actually the case for compounds II and III only: for I and IV we have e > 0 , which must mean t h a t a change in the characterization of polarization of the double bond is involved.
In l/pz-I.n Q1
FIG. 4. Reduced values ol l/r2 v s , el for copolymerization of vinylpyridazones with MMA (1) and styrene (2) within framework of the Q - e scheme.
Semilogarithmic dependences of 1It 2 o n el during copolymerization of vinylpyridazones with M M A (1) and styrene (2) are illustrated in Fig. 4 on the basis of a Q - e scheme. The variation in the angle of slope of curves 1 and 2 in Fig. 4 is due to the dissimilarity o f polarization o f the double bonds o f M M A and styrene. The relations obtained do raise the problem of how kinetic parameters are related to the structure o f the monomers. Signals of vinyl group protons of monomer IV are displaced towards stronger field compared with signals of the same protons in compounds I-III (Table 1). This means that monomer IV is less active compared with the other monomers in the pyridazone series, but the radical appertaining to IV is more active, as is borne out by values of kp and Q calculated from data on the homo- and copolymerization of vinylpyridazones presented in Tables 2 and 4. As was noted above, changes occuring in chemical shifts for 13C nuclei in the N M R spectra are only slight, as the induction effect of substituents in the hetero ring is largely attenuated on account of remoteness of the vinyl group from carbon atoms. The slight displacement of the signal of C~ in monomer IV towards a stronger field and the minimal value of CSSI for this monomer are the only grounds one has for assuming that electronegativity is lowest for the hetero aromatic substituent in compound IV, which accounts for this monomer having the highest value of e among all the vinylpyridazones under review. However, it must be said that the ~3C N M R data do not provide any clear resolution of problem of why electron
Reactivity of N-vinylpyridazonos in radical homo- and copolymerizatiou density on
>C=C<
2441
o f the vinyl g r o u p is lower f o r the studied v i n y l p y r i d a z o n e s .
F u r t h e r investigations will have to be u n d e r t a k e n to find reasons f o r the u n e x p e c t e d c h a n g e in the m a n n e r o f p o l a r i z a t i o n o f the d o u b l e bond. The kinetics of the homo- and the copolymerization were investigated by a dilatometric method in CHCI3 solution. The reaction system was degassed in a vacuum apparatus with repeated freezing in liquid nitrogen to a residual pressure of 10_ 3 GPa. The initiators (AIBN and CPC) and the inhibitor (DPPI-/) were used in the form of freshly prepared solutions. The homo- and copolymerization products were separated from Chloroform, dioxan and D M F by precipitation with diethyl ether, after which further purification was carried out by reprecipitation. Lifetimes of the propagation radicals were determined by the rotating sector method [8]. Polymerization was initiated by UV-irradiation at 30", using a DRSh-250 lamp (2 > 300 nm) The IR spectra of the monomers, homo- and copolymers were recorded (CaBr disks or films) on the ISK-29 or UR-20 equipment, and the PMR spectra on the Tesla spectrometer (80 MHz) or. the Perkin-Elmer instrument (60 MHz) in CC14, CDCI3 or trifluoroacetic acid (monomers at 20 and 60 ° and polymers at 50° using hexamethyldisiloxane as the internal standard). The 13C N M R spectra were recorded on the Bruker equipment (20 MHz) in DMSO-d6. Density values were obtained for the monomers and polymers by pycnometry in chloroform at 20 + 0"1° using the formula p = Po + (1 -Po/Px) × c [9], where p is the density of the solution (polymer •or monomer) g/ml. Contraction coefficients Ko were calculated by the equation Kc= l / p , , - 1 / p p o where p~ and pp are densities of the monomer and polymer (Table 5). TABLE 5. COEFFICIENTSOF CONTRACTIONFOR THE VINYLPYRIDAZONES (CHCI3 used as the solvent, 20 °) Compounds
Density, g/cm 2
monomer
polymer
1
1.177
1I 1II IV
1.123 1'065
1.407 1.390 1-381 1.367
1.102
KK, cm3/g 0"14 0.1") 0.21 0-18
Molecular weights of the monomers were determined by cryoscopy in dioxan or benzene, or by mass spectrometry using the Varian MAT-311 model; number-average molecular weights of the polymers were obtained with the aid of the EP-75 ebulliograph in chloroform. The composition of copolymers of vinylpyridazones with MMA and styrene were determined by spectrophotometric analysis (Specord UV-VIS equipment) in chloroform, using absorption bands, in the UV short-range portion of the spectrum, typical for vinylpyridazones. Copolymer compositions were verified in line with the results of elemental analyses. Copolymerization constants rl and r2 were calculated by an analytical method using the ES-1022 computer [10]. Trahslated by R. J. A. HENDRY
REFERENCES 1. Pat. Japan, 5124388-publ. in RefZhKhim, PS292P, 1977 2. G. V. SHATALOV, S. A. GRIDCHIN and B, I. MIKHANT'EV, In: Vsesoyuz. simpoz, po tselenapravlennomu izyskaniyu novykh fiziologicheski aktivnykh veshchestv (All-Union Syrup. on Search for Novel Physiologically Active Substances). p. 52, Zinatne, Riga, 1979
2442
P.V.
ZHIRKOV
3. S. A. GRIDCHIN, G. V. SHATALOV and B. I. MIKHANT'EV, In: Tez. dokl. Vseoyuz. konf. "Sintez i mekhanizm deistviya fiziologicheski aktivnykh veshchestv" (Abstracts of Reports of All-Union Conf. on the Synthesis and Mechanism of Action of Physiologically Active Substances), p. 109, Odessa Univ. Press, Odessa 1976 4. G. V. SHATALOV, B. I. MIKHANT'EV and S. A. GRIDCHIN, Khimiya heterotsikl, soyed., 3, 394, 1980 5. Y, MATSUBARA, K. KIYOJI, M. YOSHIHARA and T, MAESHIMA, J. Chem. Soc. Japan. Chem. and Ind. Chem., 10, 1992, 1973 6. Y, MATSUBARA, M. NOGUCHI, M. YOSHIHARA and T. MAESHIMA, Chem. Letters, 6, 601, 1973 7. D. OUDIAN, Osnovy khimii polimerov (Principles of Polymer Chemistry), Mir, Moscow, 223, 1974 8. G. P. GLADYSHEV and V. A. POPOV, Radikal'naya polimerizatsiya pri glubokikh atepenyakh prevrashcheniya (Radical Polymerization with High Degrees of Conversion). ~,Iauka, Moscow, 174, 1974 9. H. HOPFF and M. LUPPAX, Makromolek. Chem. 66: 157, 1963 I0. A. I. YEZRIELEV, E. L. BROKHINA and Ye. S. ROSKIN, Vysokomol. soyed. A l l : 8, 1670, 1969 (Translated in Polymer Sci. U.S.S.R. 11: 8, 1894, 1969)
Polymer Science U.S.S.R.
Vol. 28, No. 10. pp. 2442-2448, 1986
Printedin Poland
0032-3950/86 $10.00 + .00 © 1987PergamonJournalsLtd.
MOLECULAR M A S S DISTRIBUTION IN ISOTHERMAL RADICAL POLYMERIZATION IN A CASCADE OF IDEAL MIXING REACTORS* P. V. ZHIRKOV Institute of Chemical Physics Section, U.S.S.R. Academy of Sciences
(Received 12 March 1985) The macrokinetics of initiated radical polymerization in a cascade of ideal mixing continuous reactors is described. The degree of polymerization and the MMD range are analyzed as a function of the effective polymerization and initiation constants and of the reaction mixture feed rate. It is shown that within the technological region of change of the parameters the degree of polymerization is decreased along the cascade steps. A non-steady change in the degree of polymerization and in the MMD range with change in reagent consumption is observed. A LARGE n u m b e r o f polymers are o b t a i n e d in i n d u s t r y in cascade mixing reactors (e.g. low pressure polyethylene, polystyrene, etc.). Several pieces o f e q u i p m e n t are c o m b i n e d in sequence in a single p r o d u c t i o n chain, in each of which the reaction mixture is h o m o * Vysokomol. soyed. A28: No. 10, 2198-2203, 1986.