  We investigate the aggregation number and size distributions for
inter-molecular clusters of amphiphilic diblock and triblock copolymers in poor
solvent at very low concentrations. Diblocks and triblocks with hydrophilic
ends are shown to possess narrow distributions corresponding to formation of
monodispersed mesoglobules. Diblocks with hydrophobic ends are found to produce
inter-cluster multimers due to bridging by the hydrophilic middle blocks,
resulting in polydisperse distributions. Implications of these observations for
preparation of monodispersed nanoparticles and, potentially, understanding of
the quaternary structure of proteins are discussed.
