Structure and reactivity in cationic polymerization of butadiene derivatives. II. 1‐phenylbutadiene

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Abstract
The reactivity of 1‐phenylbutadiene (1‐PBD) in cationic polymerization and the monomer structure were investigated. 1‐PBD polymerized at −78°C in several solvents initiated by cationic catalysts such as stannic chloride and tungsten hexachloride. The polymerizations proceeded predominantly via 3,4‐type propagation mode, and gave low molecular weight polymers. More than one double bond of 1‐PBD was consumed during the polymerizations, probably due to transfer and cyclization reactions. 1‐PBD was several times as reactive as styrene and trans‐1,3‐pentadiene in copolymerizations. The Hammett plots of reactivities of ring‐substituted 1‐PBD in cationic polymerization gave the p‐value of ‐1.20, which is 0.6 times that of styrene. The 1H and 13C NMR chemical shifts of ring‐substituted 1‐PBD were measured and discussed in relation to the reaction mechanism.