137
The Free-Radical Polymerization of Bicyclobutanes T. D. Swartzl and H. K. Hall, Jr. Contribution No. 1615 f r o m the Central Research Department, Experimental Station, E. I . du Pont de Nemours and Co., Wilmington, Delaware 19898. Receiced March 12, 1970 Abstract: Free-radical reactivity ratios were determined for the copolymerization of various bicyclobutanes
possessing electronegative substituents at the bridgehead with typical vinyl monomers. The bicyclobutanes were as reactive as the vinyl compounds, a result ascribed to the high p character of the 1,3 bond. Homopolymerization of 1-bicyclobutanecarbonitrile in solution was controllable with isobutyraldehyde. Molecular weights were high ( M , = 45,000-85,000). Gel permeation chromatograms showed molecular weights skewed to the high side, owing to chain transfer with polymer followed by branching. In general, the bicyclobutanes behaved like vinyl monomers in free-radical polymerization.
T
he previous article^^^^ of this series showed t h a t bicyclobutanes carrying electronegative 1 substituents polymerize a n d copolymerize through a freeradical mechanism. T h e present paper presents re-
Reactivity Ratios. These were determined toward t h e polystyryl radical by conventional methods4 and are presented in Table I. Representative FinemanRoss plots are given i n Figures 1 a n d 2 .
Table I. Reactivity Ratios
v Styrene
Solvent DMSO
Styrene
Methyl ethyl
B
1-Bicyclobutanecarbonitrile 1-Bicyclobutanecarbonitrile
km -
kav
kvv
rv = kvB
0.16
1.35
0.12
1.43
0.12
1.43
Comments Heterogeneous
ketone
1-Bicyclobutane-
carbonitrile 1,3-Bicyclobutanedicarbonitrile 1,3-Bicyclobutanedicarbonitrile 3-Chloro-1-bicyclobutanecarbonitrile 3-Chloro-1-bicyclo-
butanecarbonitrile Methyl-l-bicyclo-
butanecarboxylate 1-Acetylbicyclo-
butane 1-Acetylbicy clo-
Styrene
y-Butyrolactone
Styrene
DMSO
Styrene
y-Butyrolactone
Styrene
DMSO
0
Styrene
y-Butyrolactone
0.05
1.77
Styrene
Methyl ethyl
0.14
1.81
0.43
0.47
1-Bicyclobutanecarbonitrile
1-Bicyclobutanecarbonitrile 1-Bicyclobutane-
0.01
Styrene
ketone DMSO
Styrene
Methyl ethyl
1.09
0.93
-0
~ 1 . 9
0.46
0.59
Methyl
ketone y-Butyrolactone
0.44
1.70
methacrylate Acrylonitrile
y-Butyrolactone
0.50
1.10
Ethyl vinyl
y-Butyrolactone
2.30
0.03
butane
ether
carbonitrile
activity ratios of these polymerizations, demonstration of chain transfer with isobutyraldehyde, a n d the X0-
rB =
s-0.;X
molecular weights a n d distributions of t h e homopolymers of 1-bicyclobutanecarbonitrile. (1) Address correspondence t o this author. (2) H. I
