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

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 degrees C.