Pressure-Dependent Clustering in Ionic-Liquid-Poly (Vinylidene Fluoride) Mixtures: An Infrared Spectroscopic Study

The nanostructures of ionic liquids (ILs) have been the focus of considerable research attention in recent years. Nevertheless, the nanoscale structures of ILs in the presence of polymers have not been described in detail at present. In this study, nanostructures of ILs disturbed by poly(vinylidene fluoride) (PVdF) were investigated via high-pressure infrared spectra. For 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([HEMIm][TFSI])-PVdF mixtures, non-monotonic frequency shifts of the C4,5-H vibrations upon dilution were observed under ambient pressure. The experimental results suggest the presence of microheterogeneity in the [HEMIm][TFSI] systems. Upon compression, PVdF further influenced the local structure of C4,5–H via pressure-enhanced IL–PVdF interactions; however, the local structures of C2–H and hydrogen-bonded O–H were not affected by PVdF under high pressures. For choline [TFSI]–PVdF mixtures, PVdF may disturb the local structures of hydrogen-bonded O–H. In the absence of the C4,5–H⋯anion and C2–H⋯anion in choline [TFSI]–PVdF mixtures, the O–H group becomes a favorable moiety for pressure-enhanced IL–PVdF interactions. Our results indicate the potential of high-pressure application for designing pressure-dependent electronic switches based on the possible changes in the microheterogeneity and electrical conductivity in IL-PVdF systems under various pressures.

Download Full-text

Characterization of Local Structures of Confined Imidazolium Ionic Liquids in PVdF-co-HFP Matrices by High Pressure Infrared Spectroscopy

Nanomaterials ◽

10.3390/nano10101973 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1973 ◽

Cited By ~ 1

Author(s):

Teng-Hui Wang ◽

Ming-Siou Wu ◽

Hai-Chou Chang

Keyword(s):

High Pressure ◽

Ionic Liquids ◽

Infrared Spectroscopy ◽

High Pressures ◽

Vinylidene Fluoride ◽

Ambient Pressure ◽

Liquid Polymer ◽

Local Structures ◽

Poly Vinylidene Fluoride

The nanoscale ion ordering of ionic liquids at confined interfaces under high pressures was investigated in this study. 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2])/poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2])/PVdF-co-HFP were prepared and characterized by using high-pressure infrared spectroscopy. Under ambient pressure, imidazolium C2–H and C4,5–H absorptions were blue-shifted in frequency due to the presence of PVdF-co-HFP. However, the absorption of anionic νa SO2 did not reveal any significant shifts in frequency upon dilution by PVdF-co-HFP. The experimental results suggest that PVdF-co-HFP disturbs the local structures of the imidazolium C–H groups instead of the anionic SO2 groups. The frequency shifts of C4,5–H became dramatic for the mixtures at high pressures. These results suggest that pressure-enhanced ionic liquid–polymer interactions may play an appreciable role in IL-PVdF-co-HFP systems under high pressures. The pressure-induced blue-shifts due to the PVdF-co-HFP additions were more obvious for the [HMIM][NTf2] mixtures than for [EMIM][NTf2] mixtures.

Download Full-text

Structural Reorganization of Imidazolium Ionic Liquids Induced by Pressure-Enhanced Ionic Liquid—Polyethylene Oxide Interactions

International Journal of Molecular Sciences ◽

10.3390/ijms22020981 ◽

2021 ◽

Vol 22 (2) ◽

pp. 981

Author(s):

Teng-Hui Wang ◽

Li-Wen Hsu ◽

Hai-Chou Chang

Keyword(s):

High Pressure ◽

Ionic Liquids ◽

Polyethylene Oxide ◽

High Pressures ◽

Ambient Pressure ◽

Structural Reorganization ◽

Imidazolium Ionic Liquids ◽

Local Structures ◽

Electronic Switches ◽

Pressure Phase

Mixtures of polyethylene oxide (PEO, M.W.~900,000) and imidazolium ionic liquids (ILs) are studied using high-pressure Fourier-transform infrared spectroscopy. At ambient pressure, the spectral features in the C–H stretching region reveal that PEO can disturb the local structures of the imidazolium rings of [BMIM]+ and [HMIM]+. The pressure-induced phase transition of pure 1-butyl-3-methylimidazolium bromide ([BMIM]Br) is observed at a pressure of 0.4 GPa. Pressure-enhanced [BMIM]Br-PEO interactions may assist PEO in dividing [BMIM]Br clusters to hinder the aggregation of [BMIM]Br under high pressures. The C–H absorptions of pure 1-hexyl-3-methylimidazolium bromide [HMIM]Br do not show band narrowing under high pressures, as observed for pure [BMIM]Br. The band narrowing of C–H peaks is observed at 1.5 GPa for the [HMIM]Br-PEO mixture containing 80 wt% of [HMIM]Br. The presence of PEO may reorganize [HMIM]Br clusters into a semi-crystalline network under high pressures. The differences in aggregation states for ambient-pressure phase and high-pressure phase may suggest the potential of [HMIM]Br-PEO (M.W.~900,000) for serving as optical or electronic switches.

Download Full-text

The crystallization behaviour and phase diagram of extended-chain crystals of poly(vinylidene fluoride) under high pressure

Polymer ◽

10.1016/0032-3861(96)81602-8 ◽

1996 ◽

Vol 37 (1) ◽

pp. 85-91 ◽

Cited By ~ 80

Author(s):

Takeshi Hattori ◽

Masamichi Hikosaka ◽

Hiroji Ohigashi

Keyword(s):

Phase Diagram ◽

High Pressure ◽

Vinylidene Fluoride ◽

Crystallization Behaviour ◽

Extended Chain ◽

Poly Vinylidene Fluoride

Download Full-text

High pressure fluid phase equilibrium data of poly(vinylidene fluoride-co-hexafluoropropylene) in carbon dioxide

Polymer Solutions - Landolt-Börnstein - Group VIII Advanced Materials and Technologies ◽

10.1007/978-3-540-88057-8_778 ◽

2009 ◽

pp. 3886-3890

Author(s):

Ch. Wohlfarth

Keyword(s):

Carbon Dioxide ◽

High Pressure ◽

Phase Equilibrium ◽

Vinylidene Fluoride ◽

Fluid Phase ◽

Phase Equilibrium Data ◽

Fluid Phase Equilibrium ◽

Poly Vinylidene Fluoride ◽

Equilibrium Data

Download Full-text

PRESSURE-INDUCED ELECTRONIC PHASE TRANSITIONS AND SUPERCONDUCTIVITY IN TITANIUM

International Journal of Modern Physics B ◽

10.1142/s0217979209051978 ◽

2009 ◽

Vol 23 (05) ◽

pp. 723-741 ◽

Cited By ~ 4

Author(s):

K. IYAKUTTI ◽

C. NIRMALA LOUIS ◽

S. ANURATHA ◽

S. MAHALAKSHMI

Keyword(s):

High Pressure ◽

Band Structure ◽

Fermi Surface ◽

High Pressures ◽

Ambient Pressure ◽

Structural Phase ◽

Normal Pressure ◽

Orbital Method ◽

Superconducting Transition ◽

Electronic Band

The electronic band structure, density of states, structural phase transition, superconducting transition and Fermi surface cross section of titanium ( Ti ) under normal and high pressures are reported. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s → d transition. On the basis of band structure and total energy results obtained using tight-binding linear muffin-tin orbital method (TB LMTO), we predict a phase transformation sequence of α( hcp ) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis, we predict a δ (distorted bcc) phase which is not stable at any high pressures. At ambient pressure, the superconducting transition occurs at 0.354 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp–Ti . On further increase of pressure, Tc begins to decrease at a rate of 1.464 K/Mbar. The highest value of Tc(P) estimated is 5.043 K for hcp–Ti , 4.538 K for ω– Ti and 4.85 K for bcc – Ti . From this, it is inferred that the maximum value of Tc(P) is rather insensitive to the crystal structure of Ti . The nonlinearities in Tc(P) is explained by considering the destruction and creation of new parts of Fermi surface at high pressure. At normal pressure, the hardness of Ti is in the following order: ω- Ti > hcp - Ti > bcc- Ti > γ- Ti .

Download Full-text

Polymorphic Extended-Chain and Folded-Chain Crystals in Poly(vinylidene fluoride) Achieved by Combination of High Pressure and Ion–Dipole Interaction

Macromolecules ◽

10.1021/acs.macromol.5b01895 ◽

2015 ◽

Vol 48 (23) ◽

pp. 8565-8573 ◽

Cited By ~ 22

Author(s):

Yue Li ◽

Saide Tang ◽

Ming-Wang Pan ◽

Lei Zhu ◽

Gan-Ji Zhong ◽

...

Keyword(s):

High Pressure ◽

Vinylidene Fluoride ◽

Dipole Interaction ◽

Extended Chain ◽

Poly Vinylidene Fluoride

Download Full-text

LEAD-CHALCOGENIDES UNDER PRESSURE: AB-INITIO STUDY

International Journal of Modern Physics Conference Series ◽

10.1142/s201019451301074x ◽

2013 ◽

Vol 22 ◽

pp. 612-618 ◽

Cited By ~ 1

Author(s):

DINESH C. GUPTA ◽

IDRIS HAMID

Keyword(s):

Phase Transition ◽

High Pressure ◽

Ab Initio ◽

Band Gap ◽

Rock Salt ◽

High Pressures ◽

Ambient Pressure ◽

High Pressure Phase ◽

Lead Chalcogenides ◽

Pressure Phase

ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.

Download Full-text