Influence of a hydrophobic core on thermoresponsive behavior of dendrimer-based star-shaped poly(2-isopropyl-2-oxazoline) in aqueous solutions

The behavior of eight-arm, star-shaped poly(2-isopropyl- 2-oxazoline) (PiPrOx(8)) with a hydrophobic dendrimer core was studied in aqueous solutions by light scattering and turbidimetry methods. In order to reveal the influence of the star-shaped structure, model linear PiPrOxs were investigated for comparison. The experiments were carried out within a 100-fold concentration interval at temperatures from 15 to 63 degrees C. Dendrimer core interaction lead to the formation of different types of aggregates at low temperatures as compared to star-shaped PiPrOx with different cores. The temperatures of the phase separation interval were determined and analyzed depending on concentration. It was shown that macromolecule shrinkage and aggregation occur below the phase separation onset which results from the specific chemical nature of macromolecules and their hydrophilic-hydrophobic balance.