1306
h4. SHIMA. D. N. BHATTACHARYYA, J. SMIDAND M. SZWARC
produce downfield shifts that decrease in magnitude as the carbon under study becomes more unsaturated. When transmitted through a double bond the effect is an upfield shift.
SATVRbTES
ALIINES
I,,*
l E R M ' h A L M O N O O L E F I N S 191 lhTERNAi
DIENES
MONOOLEFINS
$j&
113)
.;
.; 0
I7
A L K Y L BENZENES
bLLENES
,:,E
GROUPS
. ......... ...... ....
e.cH2
ms
.>50000 . . . . , "; probable values determined for three pairs of monomers; namely, 4-\kylpyridine >>50000 I o f k i i -105 styrene-p-methylstyrene, styrene-p-methoxystyrene a D . N. Bhattacharyya, C. L. Lee, J . Smid and M. Szwarc, and styrene-vinylmesitylene (see Table 111). The first J . Am. Chem. Soc., 8 5 , 533 (1963). * C. Geacintov, J. Smid and two systems were recently investigated by Tobolsky M . Szwarc, ibid., 84, 2508 (1962). c E. Ureta, unpublished and B ~ u d r e a uwho , ~ calculated the respective reactivity work from this Laboratory. d F . Bahsteter, unpublished work ratios rl and r2 from the composition of the copolymers. from this Laboratory. E C. L . Lee, J . Smid and M . Szwarc, T r a n s . Faradey Soc., in press. The U-value is calculated from The following results were reported for the reaction the ki, found in this study; the data reported in the literature ( 7 ) A 1 I ~ b o l s k yand R J Boudreau, J Polyixev Scz , 5 1 , S 5 3 ( 1 8 0 1 ) range from u = -0.1 to u = +0.1.
+ +
+
[
(1;
HAMMETT'S RELATIONS
May 3. 1963
POLYVINYLMESITYLENE-
+
IN
ANIONICC O P O L Y M E R I Z A T I O N S
1309
STYRENE.
j = t5.0
IT I
-.3
I
-.2
I
I
-.I
0 --P
I
+.I
I
1
t.2
t.3
0-.
Figure 2.
.2 .4 .6
.E 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 + t (sec.). Figure 1.
proceeding in T H F a t 0 ' with N a + as the counter-ion for the system styrene-p-methylstyrene: r1 = 1.97 and rz = 0.38 for the system styrene-P-rxethoxystyrene: r1 = 4.1 and1.q = 0.13
Our rate constants led to rl = 5.S and r2 = 0.18 for styrene-p-methylstyrene and to rl = 19 and r2 = 0,18 for styrene-p-methoxystyrene. The agreement between both sets of data is fair if one recalls t h a t our experimental conditions were different from those maintained in Tobolsky's studies, and that the conventional method of determining the reactivity ratios r1 and r2 might be uncertain when applied to anionic copolymerization.s It is gratifying to notice that in TABLE V ADDITIONOF STYRENE (1) TO VARIOUSANIONS( j ) Solvent, T H F ; T , 2 5 " ; counter-ion, h'a+ Anion
kil, l . / m o l e sec.
p-Methoxystyrenep-Methylstyrene Styrene a-MethylstyreneVinylmesitylene -
1100 1150 950 -500
l,l-Diphenylethylene-
0,3-1
2-Vinylpyridine-
L*ery low
-I i
R e f . and remarks
This This Ref. This This
work work 1 work, tetramer work, K + counter-
ion Ureta, unpublished work from this Laboratory Lee, Smid and Szwarc; Trans. Faraday Soc., in press
both investigations the spread between r1 and r2 increased when P-methoxystyrene was substituted for p-methylstyrene. This trend was indeed anticipated. The products r l ' r 2 calculated from our data are close t o unity. This also is reasonable since these monomers are very alike. The system styrene-vinylmesitylene is more complex. The two o-methyl groups prevent the coplanarity of the vinylmesitylene molecule, and this is reflected in its low ( 8 ) I
