A temperature-responsive mixed matrix membrane based on poly(ionic liquid)@poly(N-isopropylacrylaminde) microgels and polyvinylidene fluoride for the selective separation of citrus flavonoids

Herein, four novel poly(ionic liquid)@poly(N-isopropylacrylaminde) microgels were prepared and doped into polyvinylidene fluoride (PVDF) to fabricate eight temperature-responsive mixed matrix membranes (TRMs) for the efficient separation of natural citrus flavonoids, viz. naringin, neohesperidin, naringenin, and hesperetin. Dynamic light scattering of microgels in water at 20 and 50 ℃ confirmed their temperature-responsive properties. Water flux of TRMs at different temperatures proved their switchable response characteristic between 30 and 35 ℃. The mechanical property, pore size distribution, porosity, and specific surface area of these TRMs were measured. Moreover, the chemical structure, microstructure, hydrophobicity, thermostability, anti-fouling performance, and charge property were also confirmed for them. The M4 membrane exhibited a maximum separation selectivity of 81.66% at 20 ℃. Binding energy of G4 microgel to flavanone glycosides through H-bonding was greater than that of G4/flavanones. These TRMs, as a kind of novel separation materials, have the potential in the separation of various natural products.