A membrane is selective barrier that some materials can penetrate through the pores and other materials can be blocked. Recently, for the efficient separation, many researches for assigning various functionality have been received great attention. In the whole study of this thesis, the novel vapor deposition method called iCVD process (initiated chemical vapor deposition) is introduced for simply and efficiently modifying wettability of porous substrates like membranes. Owing to the advantages of vapor phase deposition, delicate substrate easily damaged by solvents can be modified. Also, the polymer film can be conformally deposited on the pattern or porous substrate. Using this iCVD process, firstly, robust superhydrophobic polymer was deposited on porous substrate. This polymer film shows superhydrophobicity as well as good chemical and mechanical stability. Second, surface energy-controlled membrane was fabricated for separating microalgal lipids from wet biomass. Third, the Janus property was assigned which has both hydrophobicity and hydrophilicity. Simple etching process was applied to superhydrophobic polymer coated porous substrate. At last, the hydrophilic and underwater oleophobic polymer was deposited on porous membrane for efficient oil/water separation including oil/water emulsion.