ATR-FTIR analysis on the pristine PP membranes showed only the expected signals of alkyl groups (Figure ) . After dopamine polymerization (PP_PDA) the IR spectra showed an additional broad signal at 3200-3500 cm -1 , which can be attributed to the presence of hydroxyl (catechol) groups of PDA . The mechanism of polydopamine adhesion on hydrophobic surfaces such as PP is not clearly understood, but it is believed to involve strong non-covalent (e.g. hydrogen bondings, hydrophobic) interactions . The peak at around 1600 cm -1 may indicate the appearance of N-H (indole) groups generated by the PDA deposition , even though superposed with the O-H bending vibration mode of adsorbed water .