Dynamic arm exchange facilitates crystallization and jamming of starlike polymers by spontaneous fine-tuning of the number of arms.

The effect of dynamic arm exchange on the crystallization and the jamming of multiarm starlike polymers was studied using small angle x-ray scattering and rheology. Poly(ethylene oxide) end capped with a small hydrophobic chain formed spherical micelles in water. Dynamic arm exchange allowed rapid crystallization and caused a discontinuous liquid-solid transition in dense suspensions after cooling. It is shown here that this is caused by spontaneous fine-tuning of the number of arms per micelle (f). Elimination of arm exchange by in situ photo-cross-linking of the core did not influence the behavior when f was at the optimum value. However, suboptimal values of f inhibited crystallization and the liquid-solid transition.