The influence of in situ modification of silica with bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT) on filler network in silica filled solution SBR compound was investigated. In situ modification greatly increased the bound rubber content. TEM observation of silica gel showed that bridging and interlocking of absorbed chains on the surface of silica particles formed the filler network. Rubber processing analyzer (RPA) was used to characterize the filler network and interaction between silica and rubber by strain and temperature sweeps. In situ modification improved the dispersion of silica, and in the meantime, the chemical bonds were formed between silica and rubber, which conferred the stability of silica dispersion during the processing. Compared to the compound without in situ modification, the compound with in situ modification of silica exhibited higher tan 8 at low strains and lower tan 8 at high strains, which can be explained in terms of filler network in the compounds. After in situ modification, DMTA results showed silica-filled SSBR vulcanizate exhibited higher tan 8 in the temperature range of -30 to 10 degrees C, and RPA results showed that it had lower tan 6 at 60 degrees C when the strain was more than 3%. (C) 2007 Wiley Periodicals, Inc.