4(%3)3 - Ecole nationale supérieure de chimie de Montpellier

While the resistance measurements give the values of appropriate pressure necessary for selfhealingin particular time period, the SEM images provided an important aspect of the healing process:that is the movement of membrane fragments towards the membrane surface in the opposite directionof the water pressure. Based on this aspect, a mechanism for the observed self-healing may be explainedon the basis of structure of the network of the micelles which are compressible under pressure in wetconditions. In case of perforation in the material, the micelles are drawn apart from each other with theABA chains pulled out and consequently dangling in the perforation space. When pressure is exerted onthe perforated film, the dynamic links between the micelles enable the network to rearrange (Figure –2.25).Figure – 2.25: Probable self-healing mechanism for the membraneThe deformation is neither instantaneous nor uniform as the bottom layer of micelles in contactwith a rigid support get deformed first followed by subsequent upper layers 32 . Hence, the compressionforces the deformed micelles to move towards the only available space, i.e. the perforation. Once themicelles of the two opposite fragments are in contact, the dangling ABA chains have enough mobility andtime to penetrate into each other’s micelle core thereby creating a bridge and ensuring the healingstability. At low pressure, the compression is too low to initiate this global movement of micelles while at70