Tuning the LCST Behavior of Poly(2-isopropyl-2-oxazoline) through Molecular Weight Control

Poly(2-isopropyl-2-oxazoline) (PiPOx) is a thermoresponsive polymer exhibiting lower critical solution temperature (LCST)-type phase transition behavior in aqueous media. Especially, its LCST (42 ℃) is close to body temperature, making it a promising candidate for biomaterials. Since LCST is generally correlated with molecular weight, identifying the exact relationship between molecular weight and LCST of PiPOx is important for designing advanced biomaterials. In this study, PiPOx homopolymers with different molecular weights were synthesized by varying synthesis parameters (e.g., reaction time) for cationic ring-opening polymerization. The molecular weight and its distribution were characterized using GPC and MALDI-TOF.

The thermoresponsive behavior of each sample was investigated in aqueous media at different concentrations. The measured cloud points were used to evaluate the effect of molecular weight on LCST-type phase behavior.

By correlating synthesis parameters, molecular weight, and LCST behavior, this study provides a strategy for tuning thermoresponsive PiPOx homopolymers.