Successive desorption experiments of water vapor in poly(methyl methacrylate) (PMMA) were performed at temperatures from 31.0 to 45.0 degrees C. The solubility of water in PMMA was found to be independent of temperature in agreement with literature findings. But the results for diffusion showed stronger dependence on water concentration than those in literature. The diffusion coefficients of water in PMMA became almost independent of temperature at high water concentrations. However, at lower water concentrations, the temperature effect on diffusion was more pronounced. The observed weak temperature dependence of diffusivity at high concentrations is likely due to a high degree of clustering of water molecules found in the PMMA we prepared. Two modified polystyrenes containing 5 and 15 mol %, respectively, 4-hydroxystyrene as comonomer units were blended with PMMA to form hydrogen-bonded polymer blends. Successive desorption experiments of water vapor in the hydrogen-bonded polymer blends were carried out at 31.0 degrees C. The solubility of water in both blends was found to increase with increasing composition of PMMA. The diffusion coefficients for PMMA and its blends increased with increasing concentration of water first, reached a maximum, then decreased with water concentration. When the desorption results were plotted with the previous study of absorption, hysteresis phenomenon of sorption existed in all blend compositions for our experimental time span.