Enhancement on Stability of Nano-Sized Titanium Dioxide in Silicone Suspension Using Diblock Copolymer: Influence of Dispersant Structure

摘要

This research investigates using of poly (dimethylsiloxane-b-hydroxy ethyl acrylate) (PDMS-b-PHEA) diblock copolymer to stabilized TiO_2 Nanoparticles in silicone fluid. The polar PHEA segment is expected to anchor on TiO_2 surface while the non-polar PDMS segment extends into silicone medium. To study effects of polymer structure on its stabilizing efficiency, PDMS-b- PHEA of structures 5-b-0.3, 5-b-1.1 and 8-b-1.0 are used. Results show that suspensions of particle with surface area ～40 and ～200 m~2/g can be stabilized for longer than 1 and 7 hrs, respectively. The copolymer with relatively long PHEA and PDMS segments is highly effective as a dispersant. This is due to enhanced adsorption on particle surface and steric stabilization. However, in the system of 40 m~2/g-TiO_2, excess amounts could lead to polymer entanglement and particle agglomeration. The copolymer dispersant exhibits high efficiency for the 200 m~2/g-TiO_2 suspension as well. In the latter system, higher concentration is required to effectively cover particle surface.