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Controlled self-/co-assembly in multi-component polymer systems towards defined micellar morphologies is subject of current research within macromolecular chemistry. The complexation between oppositely charged polyelectrolytes is a facile way to obtain micellar structures. Choosing a copolymer system, which contains a stimuli-sensitive polymer block, might further enable sequential switching of the micellar co-assemblies. We investigated the formation of interpolyelectrolyte complexes (IPEC) between a bis-hydrophilic ionic/non-ionic miktoarm star and an ionic/non-ionic and temperatureresponsive diblock copolymer. Dynamic light scattering and small-angle X-ray scattering experiments reveal the spontaneous formation of colloidally-stable micellar complexes with temperature-dependent size and aggregation number. This results from the lower critical solution temperature (LCST) behavior of the poly(N-isopropyl acrylamide) block, which is part of the diblock copolymer. Further, our studies indicate reversible structural changes of the micellar assemblies upon crossing the LCST. At T < LCST the formation of core-corona structures and at T > LCST the formation of spherical core-shell-corona assemblies is expected. Equilibration at T > LCST further seems to induce the formation of worm-like micelles apart from spherical micelles. (p. 36)