Synthesis of cyclic poly(2-ethyl-2-oxazoline) with a degradable disulfide bond

Abstract

Cyclic poly(2-ethyl-2-oxazoline) with a degradable disulfide bond was first synthesized by combining cationic ring opening polymerization and reversible thiol/disulfide exchange chemistry at a high concentration of the polymer solution.

Solvent Dependency in the Synthesis of Multiblock and Cyclic Poly(2-oxazoline)s

“…Moreover, several synthetic routes have been published for the synthesis of 2-oxazoline monomers with varying functionalities on the side chain, expanding this polymer class further . One important route to biomedically applicable polymers is via post-polymerization modification utilizing functional initiators and/or endcapping − which has been used extensively in order to create novel macromolecular architectures . These include hydrogels, − star polymers, , and graft (co)­polymers, among others.…”

“…These include hydrogels, − star polymers, , and graft (co)­polymers, among others. These architectures can often be formed using thiol–ene/yne ,,,, and copper­(I) catalysed azide alkyne cycloaddition (CuAAC) click reactions. , One architecture of particular interest is that of cyclic polymers which can be formed via the intramolecular CuAAC of heterotelechelic polymers. ,− Cyclic polymers generally have different properties compared to their linear analogues. ,− These include different cloud points, , self-assembly behavior, lower intrinsic viscosity, , and smaller hydrodynamic volumes. Specifically, cyclic poly­(2-oxazoline)­s have found use as potential biolubricants, outperforming their linear counterparts by providing a thicker film and hydration layer. ,− , One of the major limitations to the use of cyclic polymers is that very dilute or pseudo-dilute conditions have to be used in order to prevent intermolecular coupling side reactions.…”

Hybrid Multiblock Copolymers of 2-Oxazoline and Acrylates via Cu-Catalyzed Azide–Alkyne Cycloaddition Step-Growth Mechanism

“…As can be seen in Figure B, this polymerization ( SG1 ) (see Table for full details) has a low-molecular-weight peak that is slightly shifted to a lower molecular weight compared to the starting macromonomer. Such shifts to lower molecular weights are typical of cyclization side reactions on account of the smaller hydrodynamic volume of the cyclic polymer. ,− Therefore, to improve the step-growth polymerization, the polymer concentration was increased from 5.6 to 22.3 mM ( SG2 ) and then again to 33.5 mM ( SG3 ) to suppress cyclization by increasing the concentration of reactive end-groups. It should be noted that to enable a fair comparison, the concentration of CuBr and PMDETA was scaled proportionally with the concentration (Table ).…”

Poly(2‐ethyl‐2‐oxazoline) Featuring a Central Amino Moiety

“…For comparison, 1,3‐bis(bromomethyl)benzene, representing another bifunctional CROP initiator featuring the same initiation sites as 2 , was recently reported to successfully polymerize EtOx under the same reaction conditions. [ 28 ] The k p was determined as 0.02 L mol −1 min −1 (0.01 L mol −1 min −1 per initiation site), demonstrating that the bromine to iodine exchange resulted in an enhancement of the k p by one order of magnitude.…”