The invention relates to a composition containing at least one plasticizer and silicon dioxide particles having an average particle size of 150 nm or less. According to the invention, the proportion of silicon dioxide particles is from 10 to 80% by weight and the proportion of plasticizer is from 90 to 20% by weight, where the sum of the proportions of silicon dioxide particles and of the plasticizer is at least 80% by weight. The invention makes it possible to mix nanoparticles into any polymeric materials in a simple way.