Synthesis of new ionic liquid-grafted metal-oxo nanoclusters – Design of nanostructured hybrid organic-inorganic polymer networks

Abstract

Designing innovative multi-functional thermoset polymers represents a major challenge in materials science. In this work, two novel polyhedral imidazolium ionic liquid supported on oligomeric silsesquioxane nanocages having chloride (Cl−) and bistrifluoromethanesulfonimidate (NTf2-) counter anions have been synthesized. These ionic nano-objects were used to nanostructure a model epoxy network. Hence, networks displaying a homogeneous nanoscale morphology were obtained by introducing 5 wt % of such organic-inorganic (O/I) silicon-oxo clusters functionalized with ionic liquids. The obtained ionic hybrid O/I epoxy-amine networks display an excellent thermal stability (>400 °C) compared to their neat counterparts, as well as a pronounced hydrophobic character (23 mJ m−2) and good mechanical performances. Moreover, these O/I nanostructured networks demonstrate an improved fire resistance according to pyrolysis-combustion flow calorimetry (PCFC) and cone calorimetry analyses. In fact, the use of low amounts of imidazolium ionic liquid-modified polyhedral oligomeric silsesquioxanes induce a significant decrease of heat release rate (about 55%), as well as a retardation of the ignition time (close to 29%) compared to the neat epoxy-amine network.