Preparation of Polymeric Membranes and Microcapsules Using an Ionic Liquid as Morphology Control Additive

Summary Hydrophilic porous polyethersulfone (PES) membranes and microcapsules were prepared via Non‐Solvent Induced Phase Separation (NIPS) with the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) as structure control agent, added to the conventionally employed PVPK17 pore former. The introduction of [BMIM][PF 6 ] affects the phase inversion mechanism, resulting in different morphologies of the materials. Optimal conditions for the preparation of membranes (ILMs) were: 10–15 wt.% PES, 0–4 wt.% PVPK17, 5–25 wt.% [BMIM][PF 6 ], while slightly different conditions were applied for the preparation of microcapsules (ILMCs): 10% wt.% PES, 0–4% wt.% PVPK17, and 5–15 wt.% [BMIM][PF 6 ]. Thus, the produced porous spongy microcapsules (average diameter ∼800 μm) and flat sheet ionic liquid membranes (ILMs) were characterized by electronic microscopy (SEM), FTIR and Raman spectroscopy and thermal analysis. [BMIM][PF 6 ] concentration is a key factor for controlling the internal membrane morphology. Indeed, higher concentrations of [BMIM][PF 6 ] additive increases the viscosity of casting solution and reduces solvent exchange speed, thereby altering the membrane morphology from a channelled structures (finger‐like) to a spongy type.