Introduction of Carboxylate Groups at Poly(ethylene) Surfaces by Argon Plasma Immobilization of Sodium Salts of Fatty Acids

Carboxylate groups were introduced at poly(ethylene) (PE) surfaces by immobilization of sodium 10undecenoate (C11(:)) or sodium dodecanoate (C12) using an argon plasma treatment. The presence of carboxylate groupsat the surfacewas confirmedbyATR-FTIRspectroscopy, contact-angle determinations, andderivatizationXPS. Thepresence of anunsaturated bond in the alkyl chain of the surfactant enhanced the immobilization process. About 28% of the initial amount of carboxylate groups in the precoated C11(:) layer was retained at the PE surface after plasma treatment, as compared to only 6% for the C12 layer. No changes in the wettability of the modified PE surfaces were observed when they were stored at room temperature for at least 12 weeks. The use of the carboxylate groups that were introduced at polymeric surfaces with this method for further covalent coupling of other molecules is discussed.