On the plasma polymerisation of allyl alcohol: an investigation of ion–molecule reactions using a selected ion flow tube

Abstract

Low power plasmas of allyl alcohol monomer (M) have been previously probed by mass spectrometry. Mechanisms describing the formation of solid-phase product, based on ion–molecule reactions, were proposed. Major mechanisms proposed initially involve the reaction of (M-H) ⁺ ion with M, followed by a sequence of secondary ion–molecule reactions. In this paper the feasibility of these reactions has been tested using a selected ion flow tube. Parent and product ions have been monitored as a function of M concentration, providing information on the reaction rate coefficient and branching ratios, respectively. Primary and secondary products have been distinguished. The new data support the mechanism proposed for the formation of dimers and trimers in the plasma phase. However, the identity of an m/z 81 cation, previously attributed to a purely hydrocarbon containing fragment, has been revised. This ion is a primary product arising directly from reaction of (M-H) ⁺ and M, and is most likely the pyrylium cation. This new information has resulted in a significant modification to the previously proposed scheme.