(196u) Improving Gas Transport Properties of Mixed Matrix Membranes Via Interfacial Improvement

Industrialization and population growth has sped up the greenhouse gases emission and their influences on the nature [1], which have motivated the development of new materials and processes for separating and capturing the gases. Among the materials and processes, polymer membranes have several advantages, such as simplicity of operation, inexpensiveness, high efficiency and processability, over conventional methods [2]. However, the tradeoff between their permeability and selectivity is a major problem [3]. Embedding nanoparticles into polymers to prepare mixed matrix membranes (MMMs) and using gas-philic groups to facilitate gas transport are two efficient approaches to improve membrane flux and sieving ability simultaneously. MMMs are obtained by dispersion of inorganic materials into the polymer matrix. Sieving ability, extraordinary thermal stability, and high mechanical resistance of the inorganic dispersed phase and the good processability of the polymer allow for overcoming the Robeson upper bound [4]. However, there are still two challenges: the compatibility of the filler and polymer, and good dispersion. Poor compatibility results in interfacial voids, rigidification of polymer chains, and filler blockage [5]. Fixed facilitated transport allows for increasing CO₂ solubility and solubility selectivity [6]. Post modification of polymers and nanoparticles are two strategies for controlling the gas solubility. Amines, hydroxyls, tetrazole, triazine, and imidazole possess affinity towards CO₂ [7]. Dispersion of nanoparticles with amine groups improves Lewis acid–Lewis base interactions with CO₂. In addition to the interaction, better dispersion can be achieved for functionalized nanofillers [8].

As the dispersion of organic particles with amine groups allows for improving gas transport properties of MMMs via improvement of polymer-filler interface, in this paper, we present new MMMs that we prepared by embedding melamine and 2,4,6-Trihydazino-1,3,5-triazine (THDT) into PSF, which possesses excellent physical properties, thermal resistance, high glass-transition temperature (Tg), and mechanical strength. A facile and fast one-step reaction between cyanuric chloride and hydrazine was used for synthesizing THDT particles. To investigate the influence of amine groups on polymer-filler interactions, MMMs containing cyanuric chloride were also synthesized for comparison. FTIR, SEM and XRD results are presented to show scattering of the fillers in polymer, polymer-particle interactions, and morphological changes. They show satisfactory dispersion of THDT and melamine due to H-bonding interactions of the amine groups of the particles and the acceptor groups in the PSF backbone. Also, results from gas permeation tests showing the compatibility of polymer and particles arisen from interfacial interactions are presented. SEM and permeation tests indicate that the lack of polymer-particle interactions leads to interfacial voids between cyanuric chloride and polymer chains. As the THDT content increases, CO₂ permeability, CO₂/CH₄ selectivity, and CO₂/N₂ selectivity increase, propelling the gas performance towards the present upper bound. The results indicate that the synthesized THDT has the potential to improve gas transport via interfacial promotion.

References

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