A rare earth complex, La-GDTC, is investigated as novel interfacial modifier for SBR/SiO2 composites. According to model compounds, it is found that the chemical structure of La-GDTC toward silica is originated from hydrogen bonds and coordination bonds. The La-GDTC can effectively facilitate the fine dispersion of silica particles into the SBR matrix. Moreover, a jump in the normalized heat capacity Delta C-pn at the glass transition region and about 1.6-10.9% of the weight fraction of immobilized polymer layer chi im in the SBR/La-GDTC/SiO2 composites are revealed. The La-GDTC can tune the origin polymer main chain into a softer one by endowing side chains, leading to a decrease in tan delta, as well as the glass transition temperature, of SBR/La-GDTC/SiO2 composites. Mechanical properties of SBR/La-GDTC/SiO2 vulcanizates are largely improved and better than those of the SBR/ZDC/SiO2 vulcanizates. Thus, a reinforced mechanism of the La-GDTC system is proposed, which can account for the experimental observation well. (C) 2011 Elsevier Ltd. All rights reserved.