Tailored CO₂-philic Gas Separation Membranes via One-Pot Thiol–ene Chemistry

Abstract

Thiol−ene chemistry draws much attention nowadays in the construction of functional polymer materials due to its versatility and fast reaction kinetics, though only a few studies have been reported on its utilization in the fabrication of elastic polymer materials. Herein, a series of elastic, poly(dimethylsiloxane)−poly(ethylene glycol) methyl ether acrylate (PDMS−PEGMEA)-based co-polymer membranes are synthesized via a one-pot thiol−ene reaction. These membranes are highly stable and exhibit tunable thermal/ mechanical properties by tailoring the cross-linker and sidechain functionality. When used for gas separation application, all grafted elastomer membranes show excellent gas permeability and selectivity, and the membrane with an optimal composition (PDMS−PEGMEA 30 −EOPDMS 10 ) has reached the Robeson upper bound (CO 2 permeability ∼800 barrer and α[CO 2 /N 2 ] ∼39). The high permeability originates from the extremely fast chain mobility of PDMS molecules at the ambient temperature. Tailoring the PEGMEA content allows control of the α[CO 2 / N 2 ] ranging from 21 to 39 by enhancing gas solubility within the membrane matrix. This study provides a promising strategy to be utilized for the gutter layer, selective layer, or their combination in the industrial gas separation modules.

Rational Polymer Design of Stretchable Poly(ionic liquid) Membranes for Dual Applications

“…As an example, sample 1, CL-PDMS-poly­(VIMBr), shows T g ≈ 51.6 °C, consistent with previously reported linear poly­( N -vinyl diethylene glycol ethyl methyl ether imidazolium bromide), with a T g of 75 °C . A slightly lower T g value of the current system can be explained by the presence of low- T g PDMS as the backbone and cross-linker, which can increase the chain mobility. , …”

“…Therefore, the flexibility and stretchability of the developed E-PIL system may be advantageous for this application. To demonstrate their potential application as gas-separation membranes, the gas permeability of E-PIL membranes was measured in a custom-built instrument . The PIL membranes without PEGMA, including CL-PDMS-poly­(VIMBr), CL-PDMS-poly­(DEAEAH), and CL-PDMS-poly­(DEAEAMBr) all failed in the gas-separation tests due to physical rupture caused by the high fragility of membranes when applying pressure difference on two sides of the membrane.…”

“…49 A slightly lower T g value of the current system can be explained by the presence of low-T g PDMS as the backbone and cross-linker, which can increase the chain mobility. 49,50 As an initial attempt to lower the T g of obtained PIL-based membranes, the IL-monomer with larger counter ions, i.e., VIMTFSI and DEAEAH (see Scheme 1 for chemical structure), have been synthesized, following the same protocols. The ionic liquid with larger counter ions was reported to exhibit a lower T g due to the weaker ion associations.…”

Development of CO2-Selective Polyimide-Based Gas Separation Membranes Using Crown Ether and Polydimethylsiloxane

“…Notably, the gas permeability of the copolymer membranes showed a typical behavior, with a dramatic increase of many orders of magnitude when the PDMS loading rose from 10% to 20%, and further rapid growth up to 38% loading (Table 2 and Figure 7. A similar behavior of gas separation in copolymer membranes that combine the rigid polymer with PDMS has been reported in many studies [29,31,32]. This result is attributed to the percolation threshold of gas separation at a certain volume fraction of flexible PDMS loading.…”

“…This result is attributed to the percolation threshold of gas separation at a certain volume fraction of flexible PDMS loading. The permeability of the copolymer membrane containing flexible PDMS units increased slowly below a certain threshold value of PDMS (a volume fraction of 0.1-0.3) and was followed by an exponential increase in permeability above and near the threshold value [31,32]. Above the threshold value of PDMS, the copolymer became an elastomeric phase with high flexibility that allowed gas molecules to diffuse preferentially through the less-resistant PDMS microdomains and rapidly enhanced the gas permeability.…”