Abstract
Poly(ionic liquid)s are an innovative class of materials with promising properties in gas separation processes that can be used to boost the neat polymer performances. Nevertheless, some of their properties such as stability and mechanical strength have to be improved to render them suitable as materials for industrial applications. This work explored, on the one hand, the possibility to improve gas transport and separation properties of the block copolymer Pebax® 1657 by blending it with poly[3-ethyl-1-vinyl-imidazolium] diethyl phosphate (PEVI-DEP). On the other hand, Pebax® 1657 served as a support for the PIL and provided mechanical resistance to the samples. Pebax® 1657/PEVI-DEP composite membranes containing 20, 40, and 60 wt.% of PEVI-DEP were cast from solutions of the right proportion of the two polymers in a water/ethanol mixture. The PEVI-DEP content affected both the morphology of the dense membranes and gas transport through the membranes. These changes were revealed by scanning electron microscopy (SEM), time-lag, and gravimetric sorption measurements. Pebax® 1657 and PEVI-DEP showed similar affinity towards CO2, and its uptake or solubility was not influenced by the amount of PIL in the membrane. Therefore, the addition of the PIL did not lead to improvements in the separation of CO2 from other gases. Importantly, PEVI-DEP (40 wt.%) incorporation affected and improved permeability and selectivity by more than 50% especially for the separation of light gases, e.g., H2/CH4 and H2/CO2, but higher PEVI-DEP concentrations lead to a decline in the transport properties.
Highlights
The purpose of CO2 capture encourages innovative research in the design of new gas separation technologies, their industrial implementation remains a major challenge that needs to be urgently addressed [1]
Pebax® 1657 composite membranes with PEVI-DEP as polymerized ionic liquids (PILs) additive were tested for gas sorption and separation properties
The gas separation measurements by time-lag method revealed a modest improvement of permeability compared to neat Pebax® 1657 for H2, He, O2, and N2 and of selectivity in O2 /N2, H2 /CH4, and H2 /CO2
Summary
The purpose of CO2 capture encourages innovative research in the design of new gas separation technologies, their industrial implementation remains a major challenge that needs to be urgently addressed [1]. ILs possess advantageous characteristics, such as negligible vapor pressures, broad thermal stability and chemical flexibility Their ionic nature allows the modification of their physico-chemical properties through various cations and/or anions combinations [7]. The membranes produced are often prone to IL leaching from the pores [9] This issue can be solved by the exploitation of a polymerizable group on the IL cation, to create self-standing materials through a polymeric backbone. Such IL-based polymers are commonly addressed as polymeric or polymerized ionic liquids (PILs) and represent a class of polyelectrolytes [10,11,12].
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