Monte Carlo studies of isolated AB block copolymer molecules

Recent theoretical progress in understanding conformations of AB block copolymer molecules in dilute solution is reviewed. The results of the authors' own biellipsoidal smooth density model (BEM) are compared to the findings recently reported by two independent groups, for the more rigorous self-avoiding walk models with nearest neighbor interactions (SAW). The SAW results confirm the BEM conclusions for the size and shape behavior of individual blocks under changing solvent-temperature conditions. The relative orientation and separation of the blocks depend strongly, on the magnitude of AB interactions, while the individual, block parameters are much less sensitive in this respect. Parfial segregation (or partial block mixing) is the general rule rather than the exception, and is aided by the low polymer concentrations which are, found in the overlap region in dilute solutions. A unified view of homopolymers and block copolymers emerges from these models, with homopolymers being a special case of the latter group. Inherent to BEM is the arrowhead-like overall shape of the molecules, which appears to survive under most conditions.

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