The effects of post-modification treatment and chlorotrimethylsilane concentration on defiltration behaviors of pressurized liquid confined in a hydrophobic MCM-41 are investigated experimentally. If the chlorotrimethylsilane concentration is relatively low, liquid defiltration can be promoted by extensive drying at elevated temperature or extensive washing at room temperature. If the chlorotrimethylsilane concentration is relatively high, liquid defiltration becomes difficult, while the infiltration volume is larger. These phenomena can be related to the dependence of motion of liquid molecules on structures of nanopore surfaces. (c) 2008 Elsevier B.V. All rights reserved.