Simulation of the Formation of Micelles by Diblock Copolymers under Weak Segregation


Simulation of the self-assembly of diblock copolymers, ANABNB, into micelles has been performed on a cubic lattice. In all calculations, the pairwise energy of interaction of A with B is identical with the pairwise interaction (EAS) of A with a void (solvent). With this assignment of the energies, the critical micelle concentration (cmc) depends strongly on NA and the interaction parameter, which is denoted as ϰ. The cmc is weakly dependent NB if it is expressed in terms of the volume fraction of A, and NB is not too different from NA. The cmc is determined for the conditions 3 < (ϰ/z)NA < 6, where z is the lattice constant. In this range, the cmc shows an exponential dependence on ϰNA, ∂ ln VAcmc/∂[(ϰ/z)NA] ≈ −1.2. At constant ϰNA, the value of VAcmc increases slightly when NA decreases. In the micelles the insoluble block is slightly collapsed, and the soluble block becomes stretched as NB increases, with NA and the number of chains in the micelle held constant. The size of the micelle is close to that estimated by a simple hard-core shell model. © 1993, American Chemical Society. All rights reserved.

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