Thermo-Responsive Poly(2-isopropyl-2-oxazoline)-Based Bottlebrush Polymers via Cascade Enyne Metathesis Polymerization

Abstract

Poly(2-isopropyl-2-oxazoline) (PiPrOx) is a biocompatible polymer with a temperature-sensitive behavior that exhibits hydrophilic-hydrophobic phase transition in response to temperature changes via lower critical solution temperature (LCST). Typically, the LCST of PiPrOxs changes significantly depending on their molecular weight or concentration. In this study, bottlebrush polymers (PiPrOx-BPs) are created using cascade enyne metathesis polymerization of PiPrOx-based macromonomer. The unique bottlebrush shape of PiPrOx-BPs, with densely packed side chains, makes them more stable and less sensitive to changes in their size or concentration. Unlike traditional linear PiPrOx, the PiPrOx-BPs showed minimal changes in thermal transition temperatures, even with large changes in their molecular weight or concentration. The measurements showed that PiPrOx-BPs undergo sharp and consistent changes in behavior, making them more reliable for applications like sensors, drug delivery, and other systems that need precise temperature control. This research offers valuable insights into how the design of polymers can improve their performance in various practical uses.