The application of pulsed plasmas towards controlled surface functionalisation

Abstract

Pulsed plasmas were investigated as a means of controlling the composition of the surfaces generated via plasma polymerisation. A variety of precursors were studied under a range of plasma conditions using both continuous wave and pulsed plasmas. Surface and bulk analytical techniques were used to characterise the deposited plasma polymers whilst deposition rate measurements aided in understanding the effects of altering the various plasma parameters. Continuous wave plasma polymerisation of saturated cyclic fluorocarbons yielded plasma polymers with high fluorine/carbon ratios. Plasma instability at low powers limits the extent to which continuous wave power can be used to achieve good selectivity in the polymerisation process. Pulsed plasma polymerisation of perfluoroallylbenzene was studied in detail to investigate the influence of pulsing parameters on the surface composition. Highly aromatic surfaces were obtained through retention of the perfluorophenyl group from the precursor. Deposition rate experiments confirmed polymerisation was taking place in the off-portion of the duty cycle for precursors with a functional group susceptible to radical initiated reactions. A cyclic siloxane precursor with vinyl substituents was used to generate surface consisting of siloxane rings in an organic matrix. The monomer structure was retained through the reaction of the vinyl groups in the off-portion of the duty cycle. For low duty cycle pulsed plasma polymers the Si:0 ratio of the plasma polymers was identical to that of the monomer, indicating successflil retention of monomer structure using pulsed plasmas. Preliminary investigations into the pulsed plasma polymerisation of styrene oxide yielded a range of polymer compositions with varying oxygen contents. The properties of the surfaces varied with oxygen content. The results indicate that pulsed plasmas can give significant enhancements over