Thermosensitive star-shaped poly-2-ethyl-2-oxazine. Synthesis, structure characterization, conformation, and self-organization in aqueous solutions

[Display omitted] •New thermosensitive star-shaped four-arm poly-2-ethyl-2-oxazine was synthesized.•In organic solvent the arms of star-shaped polymers have a folded conformation.•At room temperature, aqueous solutions of the star were not molecularly dispersed.•At low temperatures, isolated macromolecules prevailed in star aqueous solutions.•LCST for a star-shaped poly-2-ethyl-2-oxazine is close to 53 °C. Star-shaped four-arm poly-2-ethyl-2-oxazine with calix[4]arene core was synthesized. Molar masses of the polymer star and its arms were 7100 and 1300 g·mol−1, respectively. The self-organization of molecules in aqueous solutions was investigated using light scattering and turbidity within a wide concentration interval. At room temperature, in solutions of synthesized polymer, in addition to macromolecules, a small fraction of aggregates is observed, which result from the interactions of hydrophobic branching centers. Phase separation temperatures decrease with increase in concentration. Low critical solution temperature for the investigated star-shaped poly-2-ethyl-2-oxazine is lower than LCST for aqueous solutions of linear and star-shaped poly-2-ethyl-oxazoline and higher than that for star-shaped poly-2-isopropyl-2-oxazine with calix[4]arene core and similar molar mass.