| The preparation of surfaces of controlled chemical composition, and hence with regulated physical and mechanical properties, was achieved by a combination of conventional preparative self-assembly methods and electron beam irradiation.; The electron irradiation induced cross linking processes were observed within the structure of the self-assembled monolayers (SAMs) of 4′ -hydroxy-4-mercaptobiphenyl, and the amount of the cross linked materials was directly related to the irradiation dosages received by the SAME. Both the chemical resistivity and mechanical stability of the cross linked material increased, as compared to that which remained untreated, and the non irradiated material was found to be capable of efficient intermolecular exchange for molecules of a different kind, either 4′-trifluoromethyl-4-mercaptobiphenyl or 1-octadecanethiol. As the electron irradiation dosage was efficiently monitored and was in a direct proportion to the amount of the substituted material, the SAME of controlled chemical composition of 4′-hydroxy-4-mercaptobiphenyl with 4′-trifluoromethyl-4-mercaptobiphenyl or 4 ′-hydroxy-4-mereaptobiphenyl with 1-octadecanethiol were prepared. The purely statistical nature of the electron flux resulted in randomly induced changes within the SAME structure, thus allowing preparation of mixed SAME whose surface properties varied at the molecular level.; The chemical composition of the mixed SAMs was examined by external reflection infrared spectroscopy. The intensities of the characteristic absorption signals were related to the corresponding components, and the change in composition found to be in direct proportion to the electron irradiation dosage. The wettability of the prepared surfaces as well as their topographical roughness, as imaged by atomic force microscopy, was found to be well correlated to the irradiation dosages, and hence to the chemical composition of the prepared mixed SAMS. |
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