Four types of copolymer-silica nanocomposites have been prepared via ring-opening grafting of gamma-aminopropyltrimethoxysilane (APTS) as reactive coupling agent onto preformed copolymers of maleic anhydride (MA) with 1-hexene, 1-octene, 1-dodecene and 1-octadecene and in situ hydrolysis (polycondensation) of side-chain ethoxysilane groups and tetraethoxysilane as a precursor in the presence of HCl catalyst. The copolymers of MA with 1-hexene, 1-octene and 1-dodecene were synthesized by free radical polymerization and another MA copolymer with 1-octadecene was supplied commercially as matrix copolymer. Chemical/physical structures, thermal behavior and morphology investigations of the generated hybrids were performed by FTIR, C-13, Si-29-NMR, TGA, SEM and TEM analysis methods. Nano-level hybridization through covalent bonding (amidization) between the anhydride unit of copolymers and amine group of APTS was observed, and nano-silica networks (hydrolysis) were obtained through acid catalyzed co-polycondensation of TEOS and ethoxysilane fragments from both coupling agent and precursor. Agreeing with Si-29-NMR and TGA quantitative analysis results, the degree of hydrolysis of ethoxysilane groups varied from 51.0 to 60.9%, and the content of in situ generated silica particles was found to be around 70.7-75.7%. Thermal properties and thermal stability of the obtained hybrids were found to be enhanced with silica content. SEM analysis confirmed the formation of nanostructural hybrids with relatively fine distributed nanoparticles. TEM analyses of all the nanohybrids indicate the formation of spherical morphologies. These novel copolymer hybrids are expected to be a promising and efficient organonanofiller for the preparation of polymer nanocomposites with both dual functionality and compatibilizer effects.