Star poly(2‐ethyl‐2‐oxazoline)s—synthesis and thermosensitivity

Abstract

A series of star-shaped poly(2-ethyl-2-oxazoline)s was prepared by cationic polymerization. The polymerization was initiated by dipentaerythrityl hexakis(4-nitrobenzene sulfonate) and a tosylated hyperbranched polymer of glycidol. The polymerization proceeded in a controlled manner. The star structure of the products was determined by nuclear magnetic resonance. The molar mass distributions that were measured by gel permeation chromatography with multiangle laser light scattering were narrow, and the experimental values of the molar masses were close to those predicted. The very compact structure of the polymers obtained (compared with the linear counterparts) confirmed the star formation. The star poly(2-ethyl-2-oxazoline)s show a phase transition temperature in the range 62-75 • C. Comparison of this phase transition temperature with that of the linear poly(2-ethyl-2-oxazoline)s with the same molar masses indicates the influence of molar mass and topological structure of the macromolecule on temperature behavior. The prepared copolymers are spherical, which might be useful for the controlled transport and release of active compounds.

Poly(2‐oxazoline)s as Polymer Therapeutics

“…[15], [87] while higher plurifunctional initiators give tri-, tetra- etc. arm star polymers, [88] , bow-tie multi-arm stars [35] and ultimately, macroinitiators result in comb copolymers or at high grafting densities in molecular brushes (Figure 5). [89], [90] …”

Systematic investigation of alkyl sulfonate initiators for the cationic ring-opening polymerization of 2-oxazolines revealing optimal combinations of monomers and initiators

“…Nonetheless, based on three independent reports on using sulfonate esters of pentaerythritol for the preparation of star-shaped poly(2-oxazolines) [16][17][18] it may be suggested that nosylates and triflates are better initiators than tosylates.…”

Design Strategies for Functionalized Poly(2-oxazoline)s and Derived Materials

“…In the group of tetra-or hexavalent initiators, the best results were achieved using the porphyrin-cored tetra-tosylate initiator, whereas tetra-and hexa-tosylates lead to slow initiation and ill-defined polymers. Dworak and co-workers used dipentaerythrityl hexakis (4-nitrobenzenesulfonate) and tosylated hyperbranched polymers of glycidol (the latter with 13 initiating groups) as initiators for the CROP of EtOx [119]. The monomer consumption in the range 0-70% followed first-order kinetics [initiator: dipentaerythrityl hexakis (4-nitrobenzenesulfonate)].…”