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

Figure – 4.15: The monolayer and multilayer assembly of PMMA-b-PODMA micelles over PMMA coated siliconsubstrate. While the anchoring of copolymer chains takes place via the diffusion of PMMA block in the swelledPMMA film matrix, the subsequent zipping process occurs via the interlocking of long pendant chains of PODMAblock.The assembly is further reinforced by inter-micelle zipping along lateral direction, as attested bythe observed compact assembly in AFM images. The complete coverage of the PMMA surface isprobably due to a continuous reorganization at the interface through an optimization of the PODMAchain interactions. When the immersion route was replaced by spin-coating technique, no anchoragecould be promoted with the non-swollen PMMA substrate due to the fast evaporation of the solventmixture. Hence, the physically adsorbed micelle layers got rinsed off easily when washed with the freshcyclohexane leaving the PMMA film intact, as observed by AFM and further confirmed with the contactangle value (76±3°).However, multilayers of micelles were achieved by swelling the PMMA coated silicon wafer intocyclohexane/THF (9/1 vol. %) for 15 min prior to the spin-coating of micellar solution. The contact angleof the coated surface after rinsing was found to be 89±3° and the AFM image obtained showed clearuniform assembly of micelles (Figure – 4.16a). A homogeneous multilayer coating with a thickness of114