Emulsion-Templated Monoliths Based on PIM‑1 Monomers: Hierarchical Porosity and Dye Adsorption

Polymers of intrinsic microporosity (PIMs) are linear macromolecules from rigid, twisted monomers. PolyHIPEs, macroporous polymer monoliths templated within high internal phase emulsions (HIPEs), are of interest for adsorption applications. Here, PIM-like linear polymers synthesized within oil-in-oil HIPEs generated powders. However, the addition of a cross-linking comonomer enabled, and was essential for, the generation of monoliths with densities of ∼0.08 g/cm3 and uniform, highly interconnected, open-cell structures. Interestingly, the void diameters strongly depended upon the internal phase, ∼3 μm for silicone oil and ∼52 μm for hexadecane. The unexpectedly flexible polyHIPEs exhibited poor thermal stabilities compared to PIM-1, indicating significant macromolecular differences that originate in the emulsion-templated synthesis and in the cross-linking. While the polyHIPEs synthesized at 80 °C exhibited relatively high specific surface areas (∼154 m2/g), they were far smaller than that of PIM-1. The polyHIPEs adsorbed up to ∼28 mg/g of a cationic dye but only negligible amounts (∼1 mg/g) of an anionic dye. These results demonstrate that hierarchically porous monoliths that may be of interest for adsorption applications can be generated through PIM-like syntheses within HIPEs.