Morphological control of membranes with plasma graft-filling polymerization was proposed for thick, porous membranes. The morphology depended closely on the plasma within the membrane pore, which was determined by the plasma-discharge power (PDP) and the gas pressure. The membrane morphology was investigated in terms of solvent composition in monomer solution, PDP, Ar pressure, and pore size of a substrate. Morphologies of membranes prepared were evaluated by a microscopic Fourier transform infrared mapping method. This study demonstrates that it is possible to control the membrane morphology by manipulating the plasma power and Ar pressure instead of morphological control by solvent-dependent monomer activity. Additionally, through indirect methods this study reveals that plasma exists even in sub-micropores (ca. 0.4 mum in diameter). (C) 2003 Wiley Periodicals, Inc.