Microphase separation in the bulk in ABA triblock copolymer-based model conetworks: Effects of core crowding and loop formation
SourceMacromolecular Theory and Simulations
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The microphase separation in the bulk, in the strong segregation limit, of model conetworks based on end-linked ABA triblock copolymers was investigated by calculating and minimizing the total Gibbs free energy for the various possible morphologies. The results of this study comprise a phase diagram with the prevailing morphologies mapped against junction functionality and conetwork composition, and the various geometrical parameters of the system at equilibrium, including the domain sizes and the aspect ratios. In the free-energy calculations for the assembly of the anisotropic morphologies, cylinders and lamellae, two important characteristics of the system were taken into consideration: core crowding at high core functionality, and topological loop formation upon self-assembly. The former leads to an increase in the elastic energy of the core-forming chains, whereas the latter results in a reduction in the stretching energy of the chains. The results of this study suggest that spheres are favored by a high core functionality (100-200) and a low volume fraction (≤0.15) of the A end-block, whereas lamellae are promoted by an intermediate core functionality (20-100) and a relatively high A-block volume fraction (≥0.30). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.