Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part I: Membrane Synthesis and Characterization.

Carolina Hermida-Merino,Manuel M Piñeiro,Fernando Pardo,Ane Urtiaga,Ana B Pereiro,Gabriel Zarca,João M M Araújo

doi:10.3390/nano11030607

Abstract

In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was determined by thermogravimetric analysis (TGA). The morphology of membranes was characterized using scanning electron microscope (SEM) and interferometric optical profilometry (WLOP). SEM results evidence that upon the small addition of xGnP into the IL-dominated environment, the interaction between IL and xGnP facilitates the migration of xGnP to the surface, while suppressing the interaction between IL and Pebax®1657. Fourier transform infrared spectroscopy (FTIR) was also used to determine the polymer–IoNF interactions and the distribution of the IL in the polymer matrix. Finally, the thermodynamic properties and phase transitions (polymer–IoNF) of these functionalized membranes were studied using differential scanning calorimetry (DSC). This analysis showed a gradual decrease in the melting point of the polyamide (PA6) blocks with a decrease in the corresponding melting enthalpy and a complete disappearance of the crystallinity of the polyether (PEO) phase with increasing IL content. This evidences the high compatibility and good mixing of the polymer and the IoNF.

Highlights

Reducing emissions of fluorinated gases (F-gases) is at present one of the most urgent environmental issues
The concentrations of copolymer, ionic liquids (ILs) and graphene nanoparticles are shown in Table 1 for each IoNF and functionalized membranes studied in this work
The results obtained for all IoNFs and membranes are shown in the Supporting Information

Summary

Introduction

Reducing emissions of fluorinated gases (F-gases) is at present one of the most urgent environmental issues. Ozone harmless, user safe, with low levels of flammability and toxicity, fluorinated gases are among the most powerful greenhouse gases, with a global warming effect up to 23,000 times greater than that of dioxide of carbon and lifetimes up to 50,000 year in the atmosphere. The Fgases atmospheric emissions must imperatively be reduced, in accordance with the Kyoto protocol, further developed by the Kigali agreement (international agreement specific for these compounds signed in 2016) and the most recent EU regulation [1]. The development of more benign and efficient materials designed according to the principles of green chemistry [2,3] to recover fluorinated gases used in refrigeration and air conditioning [4].

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