Studies on the thermal degradation of elastomers and their prevention have become increasingly important in view of the stringent conditions imposed in many industrial applications. One of the ways to improve thermal stability is to fabricate polymer nanocomposites. Organically modified clay (Cloisite 30B), and modified graphene (graphene oxide) were introduced into poly(ethylene-co-ethylacrylate-co-n-butylacrylate) (Polyacrylicester/PAE) matrix by solution blending process to study the effect of these layered nanofillers on thermal and mechanical properties of PAE. On incorporation of only small amount of nanofiller to the pristine PAE, temperature at which rate of degradation is maximum (Tmax) improved by 4 to 16 °C, while the modulus at 300% elongation was enhanced by almost 20–60%, depending on nature of the nanofiller. The results were interpreted with the help of transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that proper dispersion of the nanofillers increased the thermal stability of the nanocomposite to a great extent due to the interaction of the reactive groups on the surface of these fillers with the polymer and high thermal stability of these inorganic fillers. A series of Reactive Force Field (ReaxFF) molecular dynamics simulation was performed on polyacrylicester system in the presence of modified graphene (GO) molecule for the first time to understand its effect on the thermal stability of PAE. On incorporation of modified graphene inside the polymer matrix, initial and final degradation temperature along with the rate of degradation was improved to a considerable extent. Alkyl radicals, alkenes and carbon dioxide were detected as the dominant products during the reactive simulation. Other small molecular products including carbon monoxide and alkoxy radicals were discovered in the eventual products as well. The current study would help in understanding and improvement of thermal stability of various polymers.