Binary epoxy resins, diglycidyl ethers of bisphenol A and polytetramethylene glycol, were cured by binary amine hardeners, isophorone diamine and polyoxybutylene diamine, in the presence/absence of NH₂-functionalized SiO₂ nanoparticles. Four different molar ratios of the monomers were stoichiometrically used in the curing processes. The fabricated films of the epoxy thermosets were quite transparent and flexible, and fully analyzed using FE-SEM, FT-IR, XRD, and DR-UV/vis spectroscopy. The molar absorption coefficients (ɛ) of the epoxy-silica composites decreased with increasing the molar ratio of diglycidyl ether of polytetramethylene glycol and polyoxybutylene diamine in the mixtures. According to the DMA studies, no phase separation was observed in the composition of the networks obtained. When the prepared epoxy thermosets were charged by silica nanoparticles, the peaks related to the α relaxation of the polymer chains appeared at higher temperatures. Moreover, TGA measurements showed that the thermal stabilities of the resulting epoxy networks slightly increased by adding SiO₂ nanoparticles. Also, the thermal stability somewhat decreased with increasing the molar ratio of the polyoxybutylene-containing monomers.