The effect of addition of layered silicate on the order-disorder transition of poly [styrene-b-(ethylene-propylene)-b-styrene] (SEPS) block copolymer in the block copolymer/paraffin oil/layered silicate nanocomposite gels was investigated by means of differential scanning calorimetry (DSC) and modulated DSC (MDSC). The addition of layered silicate has significant influences on the order-disorder transition and the phase structure of the block copolymer. With increasing layered silicate, the order-disorder transition temperature of the block copolymer decreased. The addition of layered silicate reduced the ordering level of the block copolymer. MDSC results revealed that the order-disorder transition is a glass transition-like process. A thermal event related to the ordering process, which took place in the preparation of the sample and hid in the specimen, has been revealed by MDSC first time. (C) 2005 Elsevier B.V. All rights reserved.