New thermoresponsive star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) and poly(2-ethyl-2-oxazoline) (PEtOx) with arm grafting to upper rim of calix[8]arene core were synthesized and studied in aqueous solutions by light scattering and turbidimetry methods. The solution behavior was compared with that for polyoxazoline stars with varying positions of arm grafting, i.e., to lower rim of calix[8]arene. The observed growth of the phase separation temperature for PiPrOx as compared to PEtOx is explained by different dehydration temperatures of ethyl- and isopropyloxazoline units. The phase separation temperatures decrease after the changeover from lower rim grafting to upper rim one due to varying configurations of calix[8]arene.

The example of methanesulfonyl halides has shown the possibility of initiating cationic polymerization of 2-oxazolines by alkylsulfonic acid halides. Chain propagation rate constants and activation...

Star-shaped polymers with arms of block and gradient copolymers of 2-ethyl- and 2-isopropyl-2-oxazolines grafted to the upper rim of calix[8]arene were synthesized by the “grafting from” method. The ratio of 2-ethyl- and 2-isopropyl-2-oxazoline units was 1:1. Molar masses and hydrodynamic characteristics were measured using molecular hydrodynamics and optics methods in 2-nitropropane. The arms of the synthesized stars were short and the star-shaped macromolecules were characterized by compact dimensions and heightened intramolecular density. The influence of the arm structure on the conformation of star molecules was not observed. At low temperatures, the aqueous solutions of the studied stars were not molecular dispersed but individual molecules prevailed. One phase transition was detected for all solutions. The phase separation temperatures decreased with a growth of the content of more hydrophobic 2-isopropyl-2-oxazoline units. It was shown that the way of arms grafting to the calix[8]arene core affects the behavior of aqueous solutions of star-shaped poly-2-alkyl-2-oxazoline copolymers. In the case of upper rim functionalization, the shape of calix[8]arene resembles a plate. Accordingly, the core is less shielded from the solvent and the phase separation temperatures are lower than those for star-shaped poly-2-alkyl-2-oxazolines with lower rim functionalization of the calix[8]arene.

Starlike thermosensitive polymers were synthesized by cationic polymerization of 2-alkyl-2-oxazolines using a new type of sulfonyl chloride macroinitiator. It was confirmed that the polymerization on...