Emulsifier-free polymerization of acrylonitrile and acrylic acid in the aqueous medium was performed, and the various copolymer later membranes were prepared. The transport behavior of various volutes through water swollen membranes has been studied for hemodialysis. The results showed that the permeabilities of copolymer membranes are higher than that of Cuprophane and the solute permeability is greatly dependent on the water content of membrane. The membrane properties were considerably influenced by water content. Namely, hydrophilic portion, acrylic acid content in the membrane affects the solute permeation, mechanical properties, microstructures of membrane, and water binding properties, etc. Water structures in the copolymer membranes were investigated by differential scanning calorimetry, and the relative water increased with the increase of acrylic acid content. From the result, it is evident that the free water facilitates the solute permutation through the membrane. The microstructures of latex membranes were studied by scanning electron microscopy, and the clustered particles were observed.