An efficient pathway to the elaboration of glassy amphiphilic ester based hydroxyethyl cellulose and ionic liquids

Abstract

Hydroxyethyl cellulose (HEC) is considered one of the most important hydro-soluble cellulose derivatives, thanks to its biocompatibility and biodegradability profile. In this work, a facile synthesis methodology was developed to graft ionic liquids onto the HEC ester. Firstly, a low Tg (glass transition temperature) glassy brominated hydrophobic ester based on HEC was prepared. By regioselective nucleophilic substitution of bromine with imidazole and pyridine derivatives, HEC-ILs (ionic liquids) with a high degree of substitution were elaborated in a second step. The synthesized HEC-ILs were characterized by nuclear magnetic resonance (1H, 13C NMR), elemental analysis (CHNO), Fourier transform infrared spectroscopy-Attenuated total reflection (FTIR-ATR), X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. Zeta potential was used to verify the presence of permanent positive charge. Contact angle measurements were exploited to follow the reorganization of the surface of HEC-ILs in contact with water. A theoretical study was carried out to investigate the intra- and intermolecular interactions of polymer chains. The prepared cationic HEC derivatives have attractive properties such as their amphiphilic and glassy character, solubility in water, and a permanent positive charge. Such properties open a wide range of applications in the field of drug delivery and the complexation of anionic molecules.