The possibility to prepare composite membranes by modification of the surface of flat ultrafiltration polyacrylonitrile membranes with temperature sensitive poly(vinylalcohol-co-vinylacetal) was shown. The effects of the basic membrane type, concentration of LCST polymer and operation temperature on the transport characteristics of the modified membranes were studied. (c) 2005 Elsevier B.V. All rights reserved.