Thermo-responsive behavior of propynyl-containing hydroxyethyl starch

Thermo-responsive polymers present great advantages in the targeted delivery and release of drugs. In this study, a novel type of thermo-responsive polymer called 2-hydroxy-3-(2-propynyloxy) propyl hydroxyethyl starch (PyHES) was synthesized via hydrophobic modification of hydroxyl groups in hydroxyethyl starch (HES) with 2- propynylglycidyl ether (PGE). Aqueous PyHES solutions with an appropriate degree of substitution (DS) of hydrophobic propynyl groups exhibited strong thermo-responsive properties as well as a cloud point temperature (Tcp) that could be tuned within a range of 31 to 48 °C by changing the DS or PyHES concentrations. Moreover, the Tcp decreased with increases in the DS or the concentration of PyHES. The Tcp of PyHES had a linear relationship with DS, and DLS characterizations indicated that PyHES can form thermo-responsive micellar nanoparticles in aqueous solutions. In addition, PyHES can be further functionalized via click reaction of the propynyl group.