In this report, we synthesized poly(N-vinyl imidazole) (PNVI) grafted silica nanoparticles (SiNP) by using RAFT polymerization through grafting-from approach to demonstrate that the self-assembled structure of SiNP is the key diving force in improving physical properties of SiNP based nanocomposites. In a multistep synthetic process, well-defined PNVI chains with tunable molecular weights and surface chain densities were grown from the RAFT agent anchored SiNP surface using N-vinyl imidazole (NVI) as a monomer. Spectroscopic and thermal analysis confirmed surface grafting of PNVI on SiNP surface and the amount of grafted PNVI chins were also quantified. The mean diameter of the PNVI grafted SiNP (PNVI-g-SiNP) particles altered between 50 and 100 nm with the variation of PNVI chain lengths. The present approach is metal-catalyst free, straight forward, and provides PNVI functionalized SiNP in a simple manner in comparison to the reported methods. Further, these PNVI-g-SiNP particles were used as a nanofiller to prepare nanocomposites with Poly(4,4-diphenylether-5,5-bibenzimidazole) (OPBI). These nanocomposites displayed significantly higher mechanical, proton conductivity and less acid leaching properties than the pristine OPBI. The anisotropic self-assembled ordered structure formation of nanofillers in the nanocomposites believed to be the driving force for the enhanced physical properties. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 365-375