The pristine clay (Cloisite Na+) is modified with a half neutralized salt of three polyetheramines having different molecular weight of polyether chain. The clay is dispersed into a rubbery epoxy network. The half neutralized salt of a polyetheramine is selected in such way that it consists of a free -NH2 group which can react with the epoxy resin within the clay gallery. The intragallery reaction rate is manipulated by changing the molecular weight of polyether chain of the half neutralized salt of polyetheramine. Curing behaviors of the epoxy/clay nanocomposites were studied by using a temperature modulated differential scanning colorimetry (MDSC) under a non-isothermal condition. The intragallery reaction rate plays an important role in deciding the morphology and thermomechanical properties of the epoxy nanocomposites. A quantitative measurement of constrained region (macromolecular chains immobilized by the clay platelets) was also carried out for the epoxy nanocomposites. (C) 2015 Elsevier Ltd. All rights reserved.