Chain transfer in ethylene polymerization. V. The effect of temperature

In order to determine the effect of temperature on the chain‐transfer reaction in the free‐radical polymerization of ethylene, chain‐transfer constants were measured for sixteen transfer agents at 130°C and 200°C at 1360 atm. The results were interpreted as ΔE*, the activation energy of the chain‐transfer constant. This value is equal to the difference in activation energy between the transfer step (hydrogen abstraction) and the propagation step (addition to the monomer double bond): ΔE* = Es* − Ep*. Excellent agreement was found between measured ΔE* values determined at 1360 atm pressure and (Es* − Ep*) data for ethyl radical determined in vacuum gas‐phase reactions. Apparently, the ethyl radical is a good model for polyethyl radical. The chain‐transfer constant of ethylbenzene was found to be insensitive to temperature changes, indicating that Ep* = Es* for this compound.