Novel polysulfone (PSF) ultrafiltration membranes with pH and thermo sensitivity were prepared using the copolymer poly (N-vinylcaprolactam-co-acrylic acid) (poly (VCL-co-AA)) as an additive. The copolymer was synthesized by free radical solution polymerization, and directly blended in membrane casting solution to prepare the asymmetric membranes by phase inversion method. The presence of copolymer in blended membranes was confirmed by comparing IR spectra of plain PSF membrane and blended PSF membrane. The morphology and structure of the resulting membranes were observed by scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). The membranes were characterized in terms of pure water flux (PWF), hydraulic permeability and hydrophilicity. PWF increased from 1 to 18.8 L/m(2)h, when wt.% of copolymer increases from 0 to 2.5. Similarly, water contact angle decreased from 76 degrees to 58 degrees. The blended membranes showed evident of pH and thermo sensitivity. The stimuli responsive behaviour of membranes was also investigated in terms of pH and temperature. In addition, solution of bovine serum albumin (BSA) was used to study the permeation and antifouling performance of prepared membranes. A significant increase in BSA flux (from 0.061 L/m(2)h for plain membrane to 3.37 L/m(2)h for membrane with 6 wt.% of copolymer) and decrease in membrane fouling was observed. (C) 2014 Elsevier B.V. All rights reserved.