Improvement of dispersion and stability of fine titanium dioxides in silicone fluid using poly(ethylene oxide-b-dimethylsiloxane-b-ethylene oxide) triblock copolymer: Effects of the dispersant structure and concentration

Abstract

Suspensions of fine titanium dioxides were prepared in silicone fluid using newly synthesized poly(ethylene oxide-bdimethylsiloxane- b-ethylene oxide) triblock copolymers as dispersants. The block length of the copolymers is systematically modified to allow fine tuning of the interfacial interaction between titanium dioxide particles and the silicone medium. The properties of the suspension including its rheological behavior, sedimentation rate, particle size distribution, and particle dispersion were studied. We have found that the addition of the dispersants produces suspensions with a high shear thinning behavior, leading to a high suspension stability. Improvement of the particle dispersion by the dispersants is confirmed through particle size analysis and optical microscopy. The modification of the copolymer structure also influences the particle dispersion and stability of the suspensions. The copolymer with relatively short polyethylene oxide segments produces welldispersed and highly stable suspensions. To explain the function of the copolymers in the suspensions, particle stabilization mechanisms are suggested. This research work provides a fundamental understanding of structural-property relationships, which are important for molecular designing of polymeric dispersant for the cosmetic industry.