Gas-phase measurements of the kinetics of BF₂⁺-induced polymerization of olefinic monomers

Abstract

The initial steps in the BF 2 + -induced polymerization of the monomers of ethylene, propylene, cis-2-butene, isobutene, and styrene have been observed in the gas phase at room temperature using the Selected-Ion Flow Tube (SIFT) technique. Rate constants and product distributions have been determined for the initiation of the polymerization in each case. All five initiation reactions were found to be rapid (k ≥ 5.0 × 10 −10 cm 3 molecule −1 s −1 ). The primary product ions that propagate polymerization have been identified and sequential addition reactions have been followed in all five systems. For ethylene the energetics of the initial steps have been followed using abinitio molecular orbital theory. Reactions of BF 2 + with the vapours of water and benzene have also been characterized. Keywords: ion-induced polymerization, alkenes, kinetics, gas phase ion chemistry.