Consistently, the small shoulder observed at 1090 cm -1 may correspond to the C-C-O symmetric stretch of secondary alcohols present in the diols. However, upon functionalisation the membrane was turned hydrophilic (see water contact angle (WCA) analyses, Figure ) which creates large bands in the 3400 and 1630 cm -1 regions, hampering the observation of signature bands for amines, epoxides, or diols. a : These elements were detected in significant amounts (in some samples), but their presence is exclusively due to contaminations (either present on the original commercial membranes, or generated during the experiments). b : below detection limit. c : The value of the obtained ratio was < 0.01.