Segmented polyether-polyurethane (PU)/montmorillonite nanocomposites have been synthesized with poly(tetramethylene glycol), 4,4-diphenylmethane diisocyanate, propylenediamine, and montmorillonite. The nanoscale silicate layers are intercalated or exfoliated in the PU matrix, which are characterized by X-ray diffraction pattern and transmission electron microscopy. The PU/montmorillonite composites have been investigated by FT-IR dichroism during the stretching process in order to study the hard and soft chain orientation, hydrogen bonding, and strain induced by crystallization of the soft segment chains in PU. DSC experiment indicates that the soft phase T-g increases with the montmorillonite content. The mechanical analysis showed that tensile strength,Young's modulus, and elongation at break increase markedly, 1700% elongation at break for the composite containing 2.0 wt % montmorillonite.