Effect of phosphonium‐based ionic liquids on the structuration and physical properties of LIonomers

Abstract

In this study, LIonomers families based on phosphonium ILs have been successfully developed. These LIonomers are designed from the combination of various phosphonium‐based ionic liquids (PhILs) with different counter anions including tetradecyl (trihexyl) phosphonium bis (2,4,4‐trimethylpentyl) phosphinate (P+TMP), tributyl (ethyl) phosphonium diethyl phosphate (P+DEP), trihexyl (tetradecyl) phosphonium chloride (P+Cl) and trihexyl (tetradecyl) phosphonium acetate (P+Ac). Here, the interactions between maleic anhydride groups (MA) of the maleic anhydride‐grafted polypropylene (PPgMA) and PhILs within LIonomers have been investigated by NMR, whose intensity depends on the chemical nature of cation/anion pairs. Then, viscosity in the molten state was considered as a probe of the interaction intensity between polar groups of grafted polypropylenes and the phosphonium cation. The proper one can be tuned from the nature (P+TMP vs. P+Ac vs. P+Cl), from the steric hindrance, that is, relevant to the conformation of PhILs (P+DEP vs. P+TMP / P+Ac / P+Cl), and by MA content, as well as the extent of generated ionic chains from polar groups of matrices as “head” and associated anion/cation pairs. The effect of these generated ionic interactions on crystallization process and mechanical properties had been also investigated by DSC in non‐isothermal conditions, and tensile tests. Depending of the steric hindrance of the phosphonium ILs playing a key role on the interactions with PPgMA chains, an increase of the ductility versus a plasticizing effect can be obtained as function of the targeted applications.