Chain transfer in ethylene polymerization. VI. The effect of pressure

The chain-transfer reaction, which controls the molecular weight level of the polymer, apparently has not been studied as a function of pressure for ethylene. Therefore, the chain-transfer constants for eleven transfer agents were determined at 1360 and 2380 atm at 130°C. The results were interpreted according to transition-state theory as the difference between the volumes of activation for the transfer and propagation steps. It was found that the effect of pressure on the transfer constant is small for most transfer agents, indicating that the volumes of activation for hydrogen abstraction and addition to the ethylene double bond are similar. Aralkanes, however, gave anomalous results.