Vapor sorption isotherms of vinyl acetate (VAc) and methyl methacrylate (MMA) plasma polymer thin films are measured and compared with those for cast films of the conventionally polymerized analogs. Sorption isotherms are collected for methanol, acetone, hexane, and water at 30 degreesC using a Quartz Crystal Microbalance (QCM). The isotherms are analyzed using both Dual-Mode and Flory-Huggins sorption models. In general, plasma polymer sorption isotherms approximate those of the conventional polymer analogs, but exhibit an enhanced Langmuir-type sorption component at low activity. Accordingly, Dual-Mode model parameters show roughly equivalent Henry's Law solubility coefficient with the Langmuir-type capacity parameters (C-H') being 5-20-fold higher than those for the conventional polymer materials. (C) 2001 Elsevier Science Ltd. All rights reserved.