ABA and BAB Triblock Copolymers Based on 2‐Methyl‐2‐oxazoline and 2‐n‐Propyl‐2‐oxazoline: Synthesis and Thermoresponsive Behavior in Water

Abstract

Inspired by the well‐known amphiphilic block copolymer platform known as Pluronics or poloxamers, a small library of ABA and BAB triblock copolymers comprising hydrophilic 2‐methyl‐2‐oxazoline (A) and thermoresponsive 2‐n‐propyl‐2‐oxazoline (B) is synthesized. These novel copolymers exhibit temperature‐induced self‐assembly in aqueous solution. The formation and size of aggregates depend on the polymer structure, temperature, and concentration. The BAB copolymers tend to agglomerate in water, with the cloud point temperature depending on the length of poly(2‐n‐propyl‐2‐oxazoline) chain. On the other hand, ABA copolymers form smaller aggregates with hydrodynamic radius from 25 to 150 nm. The dependence of viscosity and viscoelastic properties on the temperature is also studied. While several Pluronic block copolymers are known to form thermoreversible hydrogels in the concentration range 20–30 wt%, thermogelation is not observed for any of the investigated poly(2‐oxazoline)s at the investigated temperature range from 10 to 50 °C.

Investigation of drug release modulation from poly(2-oxazoline) micelles through ultrasound

“…Except for the copolymer P1, which showed the highest hydrophilic fraction, all other copolymers exhibited an increase of the experimental hydrophilic molar fraction, F exp , in comparison to theoretical values F theor . This observation is in agreement with our recent experience 50 , in which a discrepancy between theoretical and experimental composition of triblock copolymers made of MetOx and nPropOx was found, also in favor of a hydrophilic fraction. Such discrepancy can be explained by an inefficient precipitation of copolymers in diethyl ether during a purification step, which led to the fractionation of the sample.…”

“…Some of the copolymers comprise the thermoresponsive nPropOx blocks (P1, P2, P5). In view of our previously published data on similar systems 50 , we conclude that these copolymers of a given composition should not exhibit a relevant thermosensitive behavior in this temperature interval. In other words, the observed release data are not influenced by this minor temperature fluctuation during the US-mediated release experiment but they are a result of mechanical effects of US on micellar structure, i.e.…”

Synthesis and Thermoresponsive Properties of Biocompatible and Biodegradable Triblock Copolymers Bearing Linear or Y‐Shaped OEG Pendants

“…Nevertheless, the FESEM indicated that both 6a and 6b self‐assembled into spherical micelle in DI water at temperatures below the T cp . Spherical micelle self‐assembled from thermoresponsive block copolymers have also been revealed in previous reports . The diameters of different polymer systems are distinct which is highly related to the structure parameters as well as solution conditions.…”

Poly(2-ethyl-2-oxazoline-co-N-propylethylene imine)s by controlled partial reduction of poly(2-ethyl-2-oxazoline)

“…We found that at 10% reduced side chains, the T g shifted to 313 K. Increasing the degree of reduction further to 25%, the T g decreased to 293 K. Samples with an even higher degree of reduction (≥ 40%) did not show a T g in our experimental setup, which agrees well with the observation by Hoogenboom and co-workers. As many water-soluble polymers 13 do, the water solubility of several POx [14][15][16] and PEtOx in particular shows a dependence on the temperature. Depending on the molar mass and the polymer architecture, the lower critical solution temperature of PEtOx ranges from 343 to about 370 K.…”