Surface tailoring of SiO2 nanoparticles by mechanochemical method based on simple milling

An appropriate modifying agent is obviously important with regard to the surface treatment of nanoparticles. Moreover, a right physical mixer that can provide enough energy to break up the secondary structure (aggregate and agglomerate) of nanoparticles is absolutely critical to the modification as well. However, it is not easy to give consideration to both of them during the process of modification. As is often the case, we tend to take care of the modifying agent but lose sight of the physical mixer. In this paper, hybrid particles of SiO₂/2,4-Diisocyanatotoluene (SiO₂/TDI) and SiO₂/2,4-Diisocyanatotoluene/hydroxyl silicone oil (SiO₂/TDI/(PDMS-OH)) were fabricated by mechanochemical method based on simple milling. The prepared hybrid particles (SiO₂/TDI and SiO₂/TDI/(PDMS-OH)) were characterized by infrared spectroscopy (FT-IR), static contact angle (CA), water sorption measurement, thermal analysis (TGA and DSC) and transmission electron microscopy (TEM). FT-IR spectra and thermal analysis (DSC) results demonstrate that TDI together with PDMS-OH is chemically anchored to the surface of nano-SiO₂. TGA results show that the grafting density of TDI is as high as 2.62 TDI/nm², while the grafting density of PDMS-OH is 0.0156 PDMS-OH/nm². Deduced from static contact angle (CA) and water sorption measurement, both hybrid particles exhibit strong hydrophobic (140^o for SiO₂/TDI and 144^o for SiO₂/TDI/(PDMS-OH)) after modification. TEM images reveal that hybrid particles (SiO₂/TDI and SiO₂/TDI/(PDMS-OH)) prepared by ball milling method exhibit much better miscibility and dispersibility in PDMS matrix when compared with those particles prepared by a common mixing device.