Supramolecular structures of uracil-functionalized PEG with multi-diamidopyridine POSS through complementary hydrogen bonding interactions

Abstract

In this study, we synthesized (i) a multi-diamidopyridine-functionalized polyhedral oligomeric silsesquioxane (MD-POSS) through nucleophilic substitution and click 1,3-cycloaddition reactions and (ii) both mono- and bis-uracil (U)-functionalized poly(ethylene glycol) derivatives (U–PEG and U–PEG–U, respectively) through Michael additions of U to acryloyl-functionalized PEG oligomers. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed that supramolecular structures self-assembled from mixtures of MD-POSS and U–PEG and from MD-POSS and U–PEG–U. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirmed the presence of multiple hydrogen bonding interactions between the diaminopyridine groups of MD-POSS and the U groups of U–PEG and U–PEG–U. Because of these strong reversible intermolecular multiple hydrogen bonds, the POSS-based polymer-like supramolecular materials exhibited improved thermal properties upon increasing the MD-POSS content.