From the Design of LIonomers to the Development of Maleic Anhydride‐Grafted‐Polypropylene ( PPgMA ) Microcellular Foams

ABSTRACT In this paper, a new route is reported to design ionic liquid branched polypropylene (PP) from the reaction of 1‐aminoethyl‐3‐methylimidazolium bromide ([AEMIM] Br) and maleic anhydride grafted‐PP (PPgMA). Therefore, LIonomers, the 2.0 generation of ionomers, have been obtained. Series of LIonomers with different structures and morphologies are prepared via (i) tuning maleic anhydride (MA) and [AEMIM] Br contents, (ii) dispersion of ionic liquid, and (iii) the ionic liquids branches assembling. The microstructure especially the location and assembling of grafted [AEMIM] Br is determined by exploring the relaxation behavior of the materials. Thus, a significant increase of the melt viscosity resulting from the ionic interactions between ionic liquid branches is evidenced by shear rheology. As a consequence, foaming behavior of the neat PP and LIonomers are investigated by using supercritical carbon dioxide (scCO 2 ) as foaming agent. All LIonomers show significantly improved foamability (expansion ratio, cell diameter, cell density and porosity) and compressive properties. These ones are mainly controlled by the assembling of ionic branches for LIonomers leading to a size of the ionic rich domains of about 60 μm. This phenomenon is attributed to the good compromise between rheological behavior and interactions established with CO 2 .