Effects of surface area and porosity on behavior of IL molecules in meso and macroporous polymeric networks. (21st December 2020)

• Record Type: Journal Article
• Authors: Raut, Prasad; Yuan, Shichen; Miyoshi, Toshikazu; Jana, Sadhan C.
• Is Part Of: Polymer. Volume 211(2020)
• Publication Date: 2020-12-21
• Subjects: Ionogel -- Ionic liquids -- Confinement in pores -- Syndiotactic polystyrene gels -- Non-bonded interactions; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2020.123081
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: In this work, ionogels fabricated by incorporating room temperature ionic liquids (ILs) in meso- and macroporous syndiotactic polystyrene (sPS) gels, are studied by using differential scanning calorimetry (DSC), polarized optical microscopy (POM), rheology, and nuclear magnetic resonance (NMR) spectroscopy. sPS gel network is prepared via thermo-reversible gelation in tetrahydrofuran and the pores are subsequently filled with the ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR14TFSI). Using DSC and POM it is found that PYR14TFSI molecules in sPS gels show higher melting temperatures than that for the neat PYR14TFSI. 1 H static NMR signals provide overall mobility of ILs in the sPS gels. Surprisingly, the ionogel prepared with 0.04 g/mL sPS solution apparently shows the broadest 1 H NMR signals among the gels prepared with 0.04, 0.08, and 0.12 g/mL sPS concentration. This is attributed to a quasi-bulk state of ILs. Moreover, two-dimensional 1 H NOESY spectra indicate that PYR14TFSI molecules in sPS show strong non-bonded through-space correlation peaks and their intensities increase proportionally with polymer concentration in the gel, while such correlation peaks are not observed for the neat PYR14TFSI molecules. The observed concentration dependence of constrained PYR14TFSI dynamics is interpreted in terms of the confined PYR14TFSI at the surface or closer to the surface of sPS scaffold. From these experimental results, it is suggested that PYR14TFSI melting-temperature are more related to quasi-bulk component than the constrained PYR14TFSI in the sPS gels. Graphical abstract: Image 1 Highlights: Ionic liquid (IL) molecules show constrained mobility in the pores of sPS gels. The fraction of IL experiencing constrained mobility increases with polymer fraction. Constrained mobility influences IL melting.