Abstract
A systematic coarse-graining procedure is proposed for the description and simulation ofAB diblock copolymers in selective solvents. Each block is represented by a small number,nA ornB, of effective segments or blobs, containing a large number of microscopic monomers.nA andnB are unequivocally determined by imposing that blobs do not, on average, overlap,even if complete copolymer coils interpenetrate (semi-dilute regime). Ultra-softeffective interactions between blobs are determined by a rigorous inversionprocedure in the low concentration limit. The methodology is applied to anathermal copolymer model where A blocks are ideal (theta solvent), B blocksself-avoiding (good solvent), while A and B blocks are mutually avoiding. Themodel leads to aggregation into polydisperse spherical micelles beyond a criticalmicellar concentration determined by Monte Carlo simulations for several size ratiosf of the two blocks. The simulations also provide accurate estimates of the osmotic pressureand of the free energy of the copolymer solutions over a wide range of concentrations. Themean micellar aggregation numbers are found to be significantly lower than those predictedby an earlier, minimal two-blob representation (Capone et al 2009 J. Phys. Chem. B 113 3629).
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