Synthesis of thermo- and pH-sensitive star-shaped poly(2-alkyl-2-oxazoline) and its properties in aqueous its properties in aqueous solutions with varying medium acidity

Abstract

pH-sensitive eight-arm star-shaped polymer with calix[8]arene core and block copolymer of poly(2-methoxycarbonylethyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline) arms was synthesized for the first time. The block composition was 1:1 and molar mass was 24000 g⋅mol−1. The behavior of synthesized star in aqueous solutions was analyzed by turbidity and light scattering at the pH values from 2 to 12.2. It is shown that in an organic solvent, the polymer molecule has a low shaped asymmetry. In aqueous solutions, the synthesized star exhibits thermosensitivity with a lower critical solution temperature. It was found that at low temperature in solutions, there were macromolecules and aggregates which were formed due to interaction of hydrophobic cores. The phase separation temperatures did not depend on pH in basic media and decreased strongly at pH <5.