Polymerization by high electric fields: Field emission and field ionization

The polymerization of styrene (St) and α‐methylstyrene (α‐MSt), initiated by high electric fields, has been investigated by using an electrode assembly comprised of a tip (sharp edge) and a flat counter electrode. Maximum specific yields obtained under field ionization (FI) conditions amount to ca. 6000 kg/Faraday (St) and 3000/Faraday (α‐MSt), respectively, and are higher than under field emission (FE) conditions: 1500 kg/Faraday (St) and 100 kg/Faraday (α‐MSt), respectively. In the case of FE initiated polymerization polymer is formed via a cationic mechanism. Part of the polystyrene formed under FE conditions is generated via free radicals. Evidence is obtained by gel permeation chromatography and scavenger experiments. A mechanism via free cations could be established for the FI initiated polymerization.