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

the micelle assembly showed the presence of multiple cracks, possibly due to weaker inter-micelleinteractions. The AFM image of a crack is shows individual 50 nm micelles aligned in short rods along thecracks. It should be noted that decreasing dramatically the block A does not alter the possibility ofgenerating flower-like micelles; however it seems to reduce bridge proportion. An explanation could bethat a shorter block A is unable to reach the hydrophobic core of another micelle while crossing itshydrophilic shell.Figure – 2.6: Scanning Electron Microscopy image (a) and Atomic Force Microscopy image (b) for copolymer filmprepared from PSAN(7.5k)-b-PEO(35k)-b-PSAN(7.5k). Despite successful assembly, the film suffers from large voidsformation due to insufficient length of PSAN block which effects the formation of bridges in between the micellesTo detect the micelle assembly, Quartz Crystal Microbalance** (QCM) was used by injectingmicellar solutions at different block copolymer concentrations onto gold-coated QCM electrodes. Whilethe PSAN(47k)-b-PEO(35k)-b-PSAN(47k) showed a clear micelle adsorption after injection (Figure – 2.7a),the PSAN(7.5k)-b-PEO(35k)-b-PSAN(7.5k) micelle adsorption was found to be very low and unstable(Figure – 2.7b). Given the fact that the gold-coated electrode is highly hydrophobic therefore only thepresence of dangling hydrophobic blocks can explain the adsorption through hydrophobic interactions.52