Behavior of Aqueous Solutions of Thermosensitive Starlike Polyalkyloxazolines with Different Arm Structures

Abstract

The behavior of aqueous solutions of starlike polyalkyloxazolines with a calix[8]arene core is investigated by light scattering and turbidimetry. Polyethyloxazoline, the gradient copolymer of ethyloxazoline and isopropyloxazoline, and the block copolymers of polyethyloxazoline and polyisopropyloxazoline are used as arms. Using the methods of molecular hydrodynamics and optics, it is shown that the arms of the studied stars are strongly folded in organic solvents. It is found that the structure of arms affects the processes of self-organization and aggregation of their macromolecules in aqueous solutions. At room temperature, the dimensions of aggregates and their fraction in solutions depend on the position of ethyloxazoline and isopropyloxazoline units with respect to the calixarene core. Introducing ethyloxazoline units into macromolecules is accompanied by an increase in both the phase-separation temperature and the width of this interval relative to the corresponding characteristics of the star with polyisopropyloxazoline arms. For stars with copolymer arms, the temperatures of the end of phase transition differ insignificantly. Differences in the behavior of the studied arms are due to the fact that the dehydration temperature for polyethyloxazoline is noticeably higher than that for polyisopropyloxazoline.