Use of structure-controlled polymers as high performance powder dispersants in the silicone oil phase.

A novel polymer dispersant with a tri-block structure was designed. The tri-block polymer was composed of polyglycerin (PGL) with two dimethylpolysiloxane chains (DMPS) at both ends of the molecular structure. The high dispersibility of the dispersant was confirmed in both a model silica system and a sunscreen formulation. The apparent silica particle size was employed as an index for the dispensability for the dispersants. The novel dispersant showed 5 times more effective than conventional one. The flow properties of a sunscreen formulation containing titanium dioxide with the novel dispersant was Newtonian, indicating that the dispersibility of the dispersant was excellent. On the other hand, the formulation with conventional dispersant showed shear-thinning flow due to aggregation of the powder. These results mean that such a tri-block copolymer would make it possible to develop consumer demanded sunscreens.