Starlike PEP-PEO block copolymer micelles offer the possibility to investigate the phase behavior and interactions of regular star polymers (ultrasoft colloids). Micellar functionality $f$ can be smoothly varied by changing solvent composition (interfacial tension). Structure factors obtained by small-angle neutron-scattering can be quantitatively described in terms of an effective potential for star polymers. The experimental phase diagram reproduces to a high level of accuracy the predicted liquid-solid transition. Whereas for intermediate $f$ a bcc phase is observed, for high $f$ the formation of a fcc phase is preempted by glass formation.

• Received 30 July 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.195504