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RESEARCH PRODUCT

Critical Micelle Concentration of Micelles with Different Geometries in Diblock Copolymer/Homopolymer Blends

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Summary In this paper, we have investigated the shape transition ofanisolatedmicelleformedintheAB-diblockcopolymerandA-homopolymer blends. SCFT has been employed tocompute the CMC for three different morphologies:lamellar, cylindrical and spherical. By comparing theCMC for different shapes, we can determine the preferredmicelle geometry. Several factors can influence the micellemorphology,andwehaveexploredtheeffectsofthediblockasymmetry, the homopolymer/copolymer length ratio andthe monomer–monomer interaction, on the micelle shapetransitions. It is found the micelle undergoes a sequenceof shape transitions, lamellar ! cylindrical ! spherical,when the A-block of the copolymer becomes longer.Previousstudieshaveshowedthesametransitionsequencebut for different ranges of homopolymer molecular weight.Mayes and de la Cruz [12] used the scaling argument andconsidered the case of k<1, while Termonia [22] carried outMonte-Carlo simulation for the system of AB diblockcopolymer in a B-selective solvent. Both studies werefocusedonthecylindricalandsphericalmicelles.Combinedwith results showed in Figure 4 (k¼1) and Figure 5 (k¼2),we can conclude that the transition from cylindrical tospherical micelle is a generic feature upon increasing the A-block length. In experiments, micelles with non-sphericalstructure were observed using transmission electronmicroscopy by Kinning et al.