This paper highlights our recent efforts to engineer polymer chains in star‐like and dendrimer‐like architectures using atom‐transfer radical polymerization (ATRP) and anionic ring‐opening polymerization (AROP) of ethylene oxide as synthetic tools. The scope and limitations of ATRP are first discussed when this method of controlled radical polymerization is applied to multifunctional initiators for the synthesis of star polymers by the core‐first approach. The switch from ATRP to AROP of ethylene oxide and vice versa allows access to branched amphiphilic block copolymers exhibiting core–shell structures. Stress is also put on the methodologies for the selective branching of polymeric chain‐ends, with a view to introducing ω‐geminal functionalities from which further polymer branches can be grown. When linear polymer precursors are used, such a strategy leads to asymmetric and mikto‐arm stars but the same can be applied to multi‐arm stars so as to generate so‐called ‘dendrimer‐like (co)polymers’ that are dendrimers with true macromolecular generations. Copyright © 2006 Society of Chemical Industry

We have performed small‐angle X‐ray scattering experiments on semi‐dilute solutions of highly charged star polyelectrolytes. Poly(sodium acrylate) (PANa) and poly(cesium acrylate) (PACs) stars with four arms were successfully synthesized by a combination of atom transfer radical polymerization and chemical modifications. Over a wide range of polyelectrolyte concentration Cp, these two systems as well as their equivalent linear polyelectrolytes were investigated at different ionic strengths. Scattering experiments show the existence of a scattering peak denoted as qmax, which disappears with the addition of a simple electrolyte, evidencing the electrostatic character of the interactions. We have also studied the effect of the charge parameter and the nature of the counterion (Na and Cs) on the scattering properties of these star polyelectrolytes. In the case of PACs, qmax scales with the polyelectrolyte concentration as Cp1/2 over the whole range of studied concentrations, whereas it scales as Cp1/2 (for Cp < 45 mg · ml−1) and Cp1/4 (for Cp > 45 mg · ml−1) in the case of PANa. Variation of qmax as a function of polyelectrolyte concentration Cp for PA1Cs (○) and PA2Cs (•) stars (error bars are indicated).magnified imageVariation of qmax as a function of polyelectrolyte concentration Cp for PA1Cs (○) and PA2Cs (•) stars (error bars are indicated).