Material : Aging mechanism in model Pickering emulsion

The chemicals used for the NPs synthesis are TetraEthylOrthoSilicate (TEOS), l-Arginine, chloride acid 0.1M and ethanol. They were supplied by Aldrich and used as received. High-purity deionized water (18.2 M.cm) was produced using Millipore Milli-Q Gradient system. The synthesis follows the same protocol as in our previous work [1]. It is performed in a 2000 ml reactor thermostated with hot water circulation at 60 ̊C and agitated by a blade mixer. The vapors are cooled in a water condenser. 1000 ml of a 6 mM l-Arginine solution is first introduced in the reactor. Once the solution reaches the desired temperature, 80 mL of TEOS is added in the reactor and form an organic phase on top of the aqueous solution. The stirring rate is fixed such that the two phases are well mixed and form an emulsion during the synthesis (1500 rpm). The reaction is kept at constant stirring speed and temperature during at least 24h and then allowed to cool down to ambient temperature. The surface modification of the particles is performed after determination of their size and concentration (i.e.their total exposed surface). A 200 mL volume of suspension is placed in a vial and agitated by a magnetic stirrer (750 rpm). A volume of 0.5 to 4 mL of trimethylethoxysilane (TMES) is added, corresponding to 2.3 to 18.2 TMES molecules/nm of particle surface and the grafting reaction is performed during 4 to 24 h. Once the reaction is complete, the particles are washed 3 to 5 times in a Millipore Amicon stirred cell (30 kDa membrane) to remove the arginine and reaction by-products. The particles are washed and redispersed in water or ethanol depending on their hydrophobicity : particles grafted with more than 9 TMES molecules/nm aggregate in water but redisperse readily when washed in absolute ethanol. The size and aggregation state of the NPs is assessed with SAXS and DLS after dialysis.