Changes in the birefringence (Delta n(NC)) of nanocomposite (NC) gels upon stretching and recovery were investigated for gels comprising a poly( N-isopropylacrylamide)-clay network structure. Irrespective of the composition of the NC gels, a change in the birefringence appeared upon stretching; DnNC varied greatly depending on the clay and water contents ( C-clay and C-w, respectively) of the gels and the stretching ratio. The NC gels with low Cclay gave rise to unique DnNC vs. strain curves with a maximum DnNC. For samples with higher Cclay, the variation of Delta n(NC)s observed in the edge-and through-directions, which is attributed to plane-orientation of the clay platelets, increased with increasing Cclay. This was confirmed by scanning electron microscopy observation, and the percentage plane-orientation was evaluated from the DnNC data. On recovery of the strain, the plane-oriented clay platelets underwent minimal reversion to the original state, although most of the PNIPA chains reverted to the random conformation. The effects of Cw on the Lambda n(NC)-strain curves were also clarified. (C) 2016 Elsevier Ltd. All rights reserved.