Near edge X-ray absorption fine structure (NEXAFS) has been employed to provide insight into the chemical nature of nitrogen in deposits formed from plasmas of allylamine and propylamine. The nitrogen K-edge spectra of these materials unambiguously demonstrate the presence of significant quantities of sp or sp 2 hybridized nitrogen. This finding, in conjunction with carbon K-edge spectra, strongly indicates that there is a substantial level of dehydrogenation during the plasma polymerization process resulting in the formation of imine groups and, at high power, nitrile groups in addition to sp 3 hybridized amines. Comparison with standard polymers indicates that amide formation (following a few days exposure to atmosphere) is negligible. These findings suggest that the hydrolysis of aminated plasma polymers may be important in their long-term aging.

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Summary: Plasma co‐polymerisation presents an exciting opportunity to produce coatings with mixtures of functional species that are difficult to achieve from single monomer systems. Unfortunately, the complexity of reactions in the plasma environment can make it difficult to predict and characterise the coating chemistries. In this study, X‐ray photoelectron (XP) and near edge X‐ray absorption fine structure (NEXAFS) spectroscopy have been used to examine coatings prepared by the co‐polymerisation of allylamine and acrylic acid. As expected, a mixture of chemical groups including amines, nitriles, amides and acids were identified. Significantly, the copolymers showed strong evidence of protonated amine (based on the N 1s XP spectra) and carboxylate anions (based on the NEXAFS O K edge); species that were not evident in coatings produced from the individual parent monomers. The results suggest that as the two monomers mix in the gas phase, allylammonium acrylate salts form and may act as a third monomer during the plasma polymerisation. The results also indicated that the addition of acrylic acid monomer suppressed the dehydrogenation of amines to nitriles and increasing the proportion of nitrogen as amine species at the interface. We speculate that these coatings will exhibit zwitterionic characteristics in aqueous solution and that they may find utility in the isoelectric focussing and separation of proteins from solution.

Our aim was to develop an improved cell transfer system for delivering laboratory-cultured human limbal epithelial cells to the cornea, which would be low risk for the patient and convenient to use for the surgeon. We took a standard contact lens and developed a plasma polymer layer for coating this for attachment of cells to the lens and subsequent transfer of cells to the cornea. A range of plasma polymer surfaces were examined for initial cell attachment using three different combinations of human and rabbit epithelial and stromal cells, initially expanding cells both with and without bovine serum. The most promising surfaces, based on acrylic acid, were then coated onto contact lenses. Cell transfer from the lenses to the denuded surface of a 3D rabbit organ culture model was then used to make a second selection of substrates, which permitted reliable cell transfer. Primary rabbit and human corneal cells attached and proliferated well on acrylic acid-coated surfaces. Reliable transfer of primary epithelial cells from the coated contact lenses to a rabbit cornea was achieved by coating lenses with acrylic acid at 5 W/10 cm(3)/min and using cell densities of 1 x 10(5)/lens and above.