Synthesis and Evaluation of Cellulose-Based, 1,2,3-Triazolium-Functionalized Polymerized Ionic Liquids: Thermal Transitions, Ionic Conductivities, and Morphological Properties

A series of 1,2,3-triazolium-functionalized cellulose derivatives were prepared using an azide–alkyne “click” cyclization strategy, followed by quaternization. As cellulose represents an inexpensive and sustainable biomacromolecule, the ability to functionalize the backbone with an ionic liquid and generate conductive materials is of great interest. Here, three different counteranions ([Br], [OTf], and [NTf2]) were employed to explore the interplay between thermal, conductive, and morphological properties using a diverse set of techniques including nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray scattering, and dielectric relaxation spectroscopy (DRS). Functionalization of native cellulose resulted in the observation of a Tg, the values of which were inversely related to the size of the counteranion. Morphological analysis of the derivatives indicated that the materials were amorphous in nature, showing a clear nanophase separation dependent on the type of anion. By simply quaternizing the 1,2,3-triazole ring to produce the corresponding ionic moiety, the ionic conductivity of the material was increased by ∼6 orders of magnitude at higher temperatures as compared to the native samples. Ionic conductivity was observed to have an Arrhenius (linear) behavior and was enhanced up to 4 orders of magnitude upon exposure to humidity. The results provided evidence to suggest that the thermal and ionic conductivity properties are dependent on anion basicity and hydration.