A thorough investigation of the interactions between silica and elastomers was conducted with the specific aim of understanding how the degree of modification with bis-triethoxysilylpropyltetrasulfane (TESPT) influences the surface energy of the filler and the tensile properties of technical compounds. The results of a thermodynamic study carried out by Inverse Gas Chromatography (IGC) at infinite dilution on silica modified with different amounts of TESPT indicate that from 6 to 8 wt% of grafted TESPT the surface activity of silica is considerably reduced and prevents particle fillers from interacting with each others. Tensile measurements at very low and high deformations carried out on vulcanised compounds loaded with silica, either unmodified or modified with different amounts of TESPT, confirm our thermodynamic predictions and further support the role of TESPT in promoting interactions between filler and elastomer, in achieving better dispersions and in improving mechanical properties. (C) 2005 Elsevier Ltd. All rights reserved.