The influences of structure parameters of polyetheramines as clay-swelling inhibitors in water-based drilling fluids on the application performances were studied. Interactions of polyetheramines with clays were investigated through elemental analysis (EA), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that lower molecular weight, hydrophobic oxypropylene segment, and plentiful amino group of polyetheramines favored improvement of inhibitive properties, enhancement of adsorption abilities, and expelling interlayer bound waters of clays (as confirmed by cutting rolling test, bentonite inhibition test, EA, XRD, and TGA studies). Simultaneously, the polyetheramines did not produce adverse effect to filtration control of the drilling fluids. In addition, XRD patterns revealed that these polyetheramines could intercalate into interlayer spaces of clays and display a monolayer arrangement. The corresponding basal spacing of clays was correlated only with molecular weight of polyetheramines. The dense loading of polyetheramines in the interlayer of clays was beneficial in improving inhibitive properties. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013