Multicenter Polyester Initiators for the Preparation of Graft Copolymers with Oligo(2‐Oxazoline) Side Chains

Abstract

Multicenter polyester initiators intended for the cationic polymerization of oxazolines were synthesized via high‐temperature polycondensation of 2‐(4‐(2‐bromoethyl)phenyl sulfonyl hydroquinone with a number of aromatic and alkylene‐aromatic dichloroanhydrides. The Kuhn segment values, liquid‐crystalline properties, and molecular‐mass characteristics of the macroinitiators are determined. The synthesized macroinitiators were used in cationic ring‐opening polymerization to obtain hybrid comb polymers containing poly(2‐oxazoline) side chains. It was suggested the method for estimating the length of poly(oxazoline) side fragments and graft density. It was demonstrated that at a certain ratio between backbone length and side chain length (which depends on chemical structure of the initiator), comb copolymers The graft copolymers form aqueous micellar solutions with a narrow particle‐size distribution. They possess a lower critical solution temperature.

Thermoresponsive Molecular Brushes with a Rigid-Chain Aromatic Polyester Backbone and Poly-2-alkyl-2-oxazoline Side Chains

“…Synthesis of the Polyester Multifunctional Macroinitiator 2-(4-(2-bromoethyl)phenylsulfonylhydroquinone was chosen as a polycondensation monomer containing functional groups suitable for initiating cationic polymerization of 2alkyl-2-oxazolines. The choice of this compound was determined by the fact that previously described [72] soluble alkylene-aromatic polyesters based on phenylsulfonylhydroquinone can be synthesized using the method of non-acceptor polycondensation. It is necessary to keep in mind that the presence of a 2-bromoethyl group sensitive to tertiary amines and alkali in the target monomer makes it impossible to apply traditional acceptor methods for polyester synthesis.…”

Loose Semirigid Aromatic Polyester Bottle Brushes at Poly(2-isopropyl-2-oxazoline) Side Chains of Various Lengths: Behavior in Solutions and Thermoresponsiveness

“…The fact that degree of polymerization of grafted chains is not proportional to initial initiator/monomer ratio is caused by chain transfer to monomer. This issue was analyzed by us earlier [59]. The observed decrease in initiation efficiency in the case of multicenter macroinitiators may be due to higher growth rate of side chains than the initiation rate; therefore, steric hindrances of side chains impede the process.…”

“…In the synthesis of the macroinitiator, high-temperature solution polycondensation without acceptor was used [72]; this method allows synthesize polyesters over a wide range of molecular masses with polydispersity index of 2.1-2.3. Synthesis of the APE O macroinitiator was conducted in accordance with that described in [59]. The conditions for the polycondensation were the following: 1-chloronaphthalene as the solvent; temperature of 200 • C, monomer concentration 25 wt.%, reaction time 2 h.…”

“…Methods and approaches to the preparation of APE O -g-PiPrOx block copolymers are described in [59]. Graft copolymers were synthesized via CROP of 2-isopropyl-2-oxazoline according to the following scheme (Figure 2):…”

“…Most solvents for such macromolecules are selective. The authors of [59] proposed the synthesis of a polycondensation APE macroinitiator containing functional groups suitable for initiating the cationic polymerization of 2-alkyl-2-oxazolines to obtain graft copolymers. Using the polymerization-polycondensation approach, stimulus-sensitive graft copolymers (APE 6 ) with an aromatic polyester backbone flexible main chain containing a -(CH 2 ) 6 -as a spacer and PEtOx side chains (APE 6 -g-PEtOx) were synthesized [60,61].…”