| Abstract: | An efficient grafting process of monofunctional alkylchlorosilanes (general formula: CH3-(CH2) n-1-Si(CH3)2Cl with n varying from 4 to 30) onto silica nanoparticules was developed by varying the surface preparation and the solvent used for the deposition process. A vapor phase deposition method was considered as reference and silicon wafers with a native SiO2 layer were used as a model surface of the silica particles. The grafting method was evaluated by studying the wettability and the grafting densities of the resulting monolayers. The chain conformation of the monolayers was determined by comparing the thickness measured by SE ellipsometry and AFM. By comparing the solvent and vapor phase deposition methods, it was demonstrated that the deposition process had a large influence on the structure of the grafted monolayers. The same structure as from a vapor phase method can be obtained from a solvent deposition process by a suitable choice of the solvent and by a strict cleaning of the surface before deposition. The grafting of much longer chains of such silane-terminated polyethylenes with different molar mass on the silica surface was also investigated in order to study the effects of the chain length on the grafting density and the layer structure. For both the short alkylchlorosilanes and polymeric grafted chains, the proposed organization of the grafted chains at the silica surface is found to be strongly dependent on the length of the alkyl chains. |
