Starlike polymer brushes in Θ-solvent

The properties of starlike polymer brushes in Θ-solvent are investigated using molecular dynamics simulations, scaling- and mean-field theory. Deviations of layer thickness and monomer density from predictions of scaling theory are analyzed and explained. Contrary to common believes, we conclude that the Alexander-deGennes scaling theory is not valid for starlike polymer brushes in Θ-solvent, unless the grafting density is extremely low. A comparison with structural and dynamical properties of starlike polymer brushes in good solvent is carried out. Previous studies in good solvent reported about the dual-population structure of these branched polymer brushes, with coexisting phases of stretched and retracted molecules; the same separation emerges in Θ-solvent, though at higher grafting densities. Molecular tension and population fractions are shown to be solvent-dependent, and a reduced dynamical flip-rate between the two populations is observed for the case of the Θ-brush.