pH degradable dendron-functionalized poly(2-ethyl-2-oxazoline) prepared by a cascade “double-click” reaction

Abstract

In this study, we report on the synthesis of a dendron-functionalized poly(2-ethyl-2-oxazoline) in a one-pot cascade reaction approach. By means of a bifunctional small organic compound linker, namely (9-azidomethyl)anthracene, alkyne-functionalized PEtOx and maleimide-substituted dendron were coupled in a one-pot cascade approach exploiting the copper-catalyzed azide-alkyne cycloaddition (CuAAC) and the Diels–Alder cycloaddition. The resulting amphiphilic block copolymer was characterized by size-exclusion chromatography (SEC), proton nuclear magnetic resonance (1H NMR) spectroscopy and matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry (MS). Since the dendron contains acid-labile acetal protecting groups, it is pH responsive and the hydrophilicity significantly increases upon hydrolysis. The aqueous solution behavior and pH-responsivity of the PEtOx–dendron are discussed at neutral pH as well as acidic pH based on dynamic light scattering and fluorescence spectroscopy.