An investigation of the mechanisms of plasma polymerisation of allyl alcohol

Abstract

Inductively coupled, radiofrequency-induced plasmas of allyl alcohol, operated at low electrical power (1–8 W), have been investigated using mass spectrometry (MS) and deposition rate measurements. The solid, plasma polymer product was collected on silicon substrates and analysed by X-ray photoelectron spectroscopy (XPS). The positive-ion MS data indicate that species of the form (M-H)⁺, (2M-H)⁺ and (3M-H)⁺, where M represents a unit of the starting material, are present in the plasma. The relative abundance of these was monitored as a function of the electrical power supplied to the plasma. No neutral oligomeric species were detected. XPS analysis reveals an inverse relationship between power and retention of alcohol functionality in the solid product. Comparison of the MS and XPS results suggests that the above cationic oligomers are responsible for alcohol retention, whereas fragmentation events lead to the introduction of new functional groups. The thin film which featured the highest degree of retention of alcohol (65%) was obtained from a plasma operated at 1 W, but was deposited at the lowest rate (1.81 ng s^-1).

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