The Effect of Reactive Ionic Liquid or Plasticizer Incorporation on the Physicochemical and Transport Properties of Cellulose Acetate Propionate-Based Membranes

Abstract

Pervaporation is a membrane-separation technique which uses polymeric and/or ceramic membranes.In the case of pervaporation processes applied to dehydration, the membrane should transport water molecules preferentially. Reactive ionic liquid (RIL) (3-(1,3-diethoxy-1,3-dioxopropan-2-yl)-1-methyl-1H-imidazol-3-ium) was used to prepare novel dense cellulose acetate propionate (CAP) based membranes, applying the phase-inversion method. The designed polymer-ionic liquid system contained ionic liquid partially linked to the polymeric structure via the transesterification reaction. The various physicochemical, mechanical, equilibrium and transport properties of CAP-RIL membranes were determined and compared with the properties of CAP membranes modified with plasticizers, i.e., tributyl citrate (TBC) and acetyl tributyl citrate (ATBC). Thermogravimetric analysis (TGA) testified that CAP-RIL membranes as well as CAP membranes modified with TBC and ATBC are thermally stable up to at least 120 • C. Tensile tests of the membranes revealed improved mechanical properties reflected by reduced brittleness and increased elongation at break achieved for CAP-RIL membranes in contrast to pristine CAP membranes. RIL plasticizes the CAP matrix, and CAP-RIL membranes possess preferable mechanical properties in comparison to membranes with other plasticizers investigated. The incorporation of RIL into CAP membranes tuned the surface properties of the membranes, enhancing their hydrophilic character. Moreover, the addition of RIL into CAP resulted in an excellent improvement of the separation factor, in comparison to pristine CAP membranes, in pervaporation dehydration of propan-2-ol. The separation factor β increased from ca. 10 for pristine CAP membrane to ca. 380 for CAP-16.7-RIL membranes contacting an azeotropic composition of water-propan-2-ol mixture (i.e., 12 wt % water).

The Impact of Reactive Ionic Liquids Addition on the Physicochemical and Sorption Properties of Poly(Vinyl Alcohol)-Based Films

“…The sorption results of PVA-RIL membranes in H 2 O, EtOH and IPA showed that PVA-RIL membranes have significantly higher affinity to water and the results are consistent with the pervaporation findings of Kujawski et al [ 59 ], Chaudhari et al [ 60 ] and Rynkowska et al [ 30 ] research. Kujawski et al [ 59 ] investigated the properties of PVA-based membranes (Pervap TM ) used for tetrafluoropropanol dewatering.…”

“…This is related to the strong interactions occurring between membrane and water molecules because of the interactive groups such as hydroxyl and –COO– ester groups present in PVA-RILs membranes which was confirmed by the FTIR-ATR results. Rynkowska et al [ 30 ] investigated the swelling behavior of RIL1_Br incorporated CAP membranes. It was found that the incorporation of RIL1_Br enhanced the CAP-based membranes swelling in water comparing with pure CAP membrane.…”

“…On the contrary, the CAP-based membranes swelling in organic solvents (EtOH and IPA) is reduced. This behavior results from the RIL1_Br hydrophilic character [ 30 ]. Those results are consistent with the data obtained in this research.…”

“…Moreover, they contain functional groups, which can react with polymers to create covalent bonds between RILs and polymers. For instance, (3-(1,3-diethoxy-1,3-dioxopropan-2-yl)-1-methyl-1H-imidazol-3-ium) RIL was used for the elaboration of dense cellulose acetate propionate (CAP) based membranes [ 30 ]. CAP modification with RIL via the transesterification reaction led to the partial substitution of CAP functional groups with RIL.…”

“…CAP modification with RIL via the transesterification reaction led to the partial substitution of CAP functional groups with RIL. That led to the change of mechanical properties, thermal properties and swelling ability [ 30 ]. Therefore, polymeric membranes with the ionic liquids have found various applications including pervaporation [ 1 , 2 , 3 ], gas separation [ 24 , 31 ], and proton exchange membrane fuel cells [ 32 , 33 , 34 ].…”