Electrospun nanofibrous membranes (ENMs) are an emerging material in the filtration space. However, widespread adoption of these materials has been hindered by poor mechanical strength thus necessitating the use of an additional support layer which can add to membrane thickness and resistance. The poor mechanical strength of ENMs are mostly due to their high porosity compounded with weak bonding at fiber junctions. In this study, we demonstrate a post-treatment approach to improve the mechanical properties of two commonly used membrane polymers: polyacylonitrile (PAN) and polysulfone (PSu). This post-treatment involves exposing ENMs to the solvent vapor where the mechanical strength is improved by the solvent-induced fusion of inter-fiber junction points. The treated membranes showed significant enhancement on tensile strength and Young's Modulus while high porosity and water permeability were retained. (c) 2013 Elsevier B.V. All rights reserved.