Static time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed for acquiring the high-resolution surface spectra of four types of synthesized imidazolium ionene membranes. These novel membranes have aromatic ether–ketone–ether linkages inspired by poly(ether ether ketone) (PEEK). The PEEK-ionenes synthesized for this study have imidazolium cations placed in the polymeric backbone with bistriflimide [Tf2N] counterions. The attention given to synthetically modified PEEK derivatives, such as PEEK-ionenes, is considerable due to their ability to selectively capture CO2 molecules and other light gases. Therefore, it is important to characterize the surface of these synthesized novel PEEK-ionenes. In this work, characteristic and unique peaks were identified in the positive spectra of each sample. The differences in mass spectra among the samples provide insights for optimizing or fine-tuning the PEEK-ionenes synthesis to achieve a high-performance CO2 separation membrane with enhanced permeability, selectivity, and mechanical stability. The SIMS spectra and identified characteristic peaks of these synthesized ionenes will serve as a reference in the positive mode, complementing the corresponding spectra reported in the negative ion mode (Paper II).

  • Accession#: 01886, 01887, 01888, and 01889

  • Technique: SIMS

  • Specimen: PEEK-ionenes

  • Instrument: ION-TOF TOF-SIMS 5

  • Major Species in Spectra: C, N, O, F, and S

  • Minor Species in Spectra: None

  • Published Spectra: 4

  • Spectral Category: Reference

Poly(ether ether ketone) (PEEK) and related materials are well known for their exceptional chemical, thermal, and mechanical stability, as well as biocompatibility.1,2 Inspired by the ultrahigh-performance (UHP) polymer region of PEEK, a novel approach of producing PEEK-ionene has been developed in Bara’s group for achieving outstanding properties toward high-performance gas separation membrane applications.3 

Considerable efforts were made to design and develop the key monomers of PEEK-ionenes, aiming to enhance the selectivity and permeability of light gases, as well as other properties such as mechanical and thermal stabilities. Four types of PEEK-ionenes analyzed in this work are the ionic polymers where the imidazolium cation resides in the PEEK backbone and with the incorporation of bistriflimide [Tf2N]. This anion was selected as the counterion in that it is thermal and mechanical stability and, thus, suitable for making thin film for study as membranes.4 The monomer of each PEEK-ionene differs in the ether–ketone–ether (EEK) linkage backbone with or without xylene linkage, number of the imidazolium cations incorporated in the PEEK backbone, and arrangement of ether–ether–ketone linkages, as shown in Fig. 1. The variation and mediation of backbone linkages and imidazolium cations may change their corresponding functional roles, which influence the affinity for certain light gases (CO2 and CH4) and organization of the polymer matrix.

FIG. 1.

Chemical structures and formulas of four PEEK-ionenes analyzed by static ToF-SIMS in this work, including (a) p([K(EEK)2(2mIm)6(C6)5][Tf2N]6), (b) p([K(EEK)2(2mIm)4(C6XylC6)][Tf2N]4), (c) p([K(EEK)2(2mIm)4(XylC6Xyl)][Tf2N]4), (d) p([K(EEK)2(2mIm)4(C6C6C6)][Tf2N]4, and the anion (e) Tf2N.

FIG. 1.

Chemical structures and formulas of four PEEK-ionenes analyzed by static ToF-SIMS in this work, including (a) p([K(EEK)2(2mIm)6(C6)5][Tf2N]6), (b) p([K(EEK)2(2mIm)4(C6XylC6)][Tf2N]4), (c) p([K(EEK)2(2mIm)4(XylC6Xyl)][Tf2N]4), (d) p([K(EEK)2(2mIm)4(C6C6C6)][Tf2N]4, and the anion (e) Tf2N.

Close modal

The first example of PEEK-ionene was characterized by 1H nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) mass spectrometry (MS). Although NMR and FTIR can provide identification and quantification of functional groups, they are not able to focus on sample surface where the polymers interact with gases in the first place. The results from MALDI-ToF MS were not able to distinguish specific ions.3 Besides, MALDI-TOF MS is limited by the sensitivity, affected by the matrix effect, and low in discriminatory power resulting in being unable to differentiate similar chemical species.5 

Static time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an ideal tool for characterizing PEEK-ionene membrane due to its chemical specificity and surface sensitivity. An earlier attempt was made to characterize the surface spectra of PEEK-ionene using ToF-SIMS.6 However, that work did not detect the molecular ions of imidazolium cation or Tf2N anion. This report includes the full spectra of four types of PEEK-ionene membranes acquired in positive ion mode, using ToF-SIMS 5 (IONTOF, Germany). A low analysis current (0.0002 nA) was applied to avoid peak intensity saturation. Samples No. 1 and 4, membranes were cut into ∼8 × 8 mm2 square piece and mounted on a ToF-SIMS sample holder. Samples No. 2 and 3 were in powder form. They were pressed onto indium foils before mounting separately. 50 keV Bi3++ was applied as the analysis beam. Characteristic peaks of each sample that reflecting their respective chemical structures were identified.

The rapid development and growing interest in the preparation of polymetric membranes for gas separation urge us to have better understanding of the customized membrane and the role of its functional groups. This work can provide complementary information to other analytical techniques (NMR) to understand the role of functional groups in each specifically designed PEEK-ionenes and ultimately guide the production and design of high-performance gas separation membranes.

The spectra presented here are also companion to the Part II negative ion mode dataset.7 

Specimen: Synthesized PEEK-ionene sample No. 1

CAS Registry #: N/A

Specimen Characteristics: Homogeneous; solid; unknown crystallinity; unknown conductivity; polymer

Chemical Name: PEEK-ionene

Source: Synthesized at University of Alabama

Specimen Composition: N/A

Form: Film

Structure: p([K(EEK)2(2mIm)6(C6)5][Tf2N]6)

History and Significance: PEEK-ionene is developed and optimized for gas separation with improved selectivity and permeability. Polymetric membranes for gas separation are rapidly developing with growing interest.

As Received Condition: As-received film

Analyzed Region: 200 × 200 μm2

Ex Situ Preparation/Mounting: ∼8 × 8 mm2 membrane piece was cut from the membrane film and stabilized on a back-mount holder.

In Situ Preparation: N/A

Charge Control Conditions and Procedures: Low-energy electrons

Temp. During Analysis: 298 K

Pressure During Analysis: 2.1 × 10−5 Pa

Pre-analysis Beam Exposure: N/A

Specimen: Synthesized PEEK-ionene sample No. 2

CAS Registry #: N/A

Specimen Characteristics: Homogeneous; solid; unknown crystallinity; unknown conductivity; polymer; powder

Chemical Name: PEEK-ionene

Source: Synthesized at University of Alabama

Specimen Composition: N/A

Form: Dark brown powder

Structure: p([K(EEK)2(2mIm)4(C6XylC6)][Tf2N]4)

History and Significance: PEEK-ionene is developed and optimized for gas separation with improved selectivity and permeability. Polymetric membranes for gas separation are rapidly developing with growing interest.

As Received Condition: As-received powder

Analyzed Region: 200 × 200 μm2

Ex Situ Preparation/Mounting: ∼100 mg of powder was pressed into an indium foil (5 × 5 mm2), and the latter was stabilized on a top-mount holder.

In Situ Preparation: N/A

Charge Control Conditions and Procedures: Low-energy electrons

Temp. During Analysis: 298 K

Pressure During Analysis: 4.3 × 10−6 Pa

Pre-analysis Beam Exposure: N/A

Specimen: Synthesized PEEK-ionene sample No. 3

CAS Registry #: N/A

Specimen Characteristics: Homogeneous; solid; unknown crystallinity; unknown conductivity; polymer; powder

Chemical Name: PEEK-ionene

Source: Synthesized at University of Alabama

Specimen Composition: N/A

Form: Light brown powder

Structure: p([K(EEK)2(2mIm)4(XylC6Xyl)][Tf2N]4)

History and Significance: PEEK-ionene is developed and optimized for gas separation with improved selectivity and permeability. Polymetric membranes for gas separation are rapidly developing with growing interest.

As Received Condition: As-received powder

Analyzed Region: 200 × 200 μm2

Ex Situ Preparation/Mounting: ∼100 mg of powder was pressed into an indium foil (5 × 5 mm2), and the latter was stabilized on a top-mount holder.

In Situ Preparation: N/A

Charge Control Conditions and Procedures: Low-energy electrons

Temp. During Analysis: 298 K

Pressure During Analysis: 6.3 × 10−6 Pa

Pre-analysis Beam Exposure: N/A

Specimen: Synthesized PEEK-ionene sample No. 4

CAS Registry #: N/A

Specimen Characteristics: Homogeneous; solid; unknown crystallinity; unknown conductivity; polymer

Chemical Name: PEEK-ionene

Source: Synthesized at University of Alabama

Specimen Composition: N/A

Form: Dark brown powder

Structure: p([K(EEK)2(2mIm)4(C6C6C6)[Tf2N]4)

History and Significance: PEEK-ionene is developed and optimized for gas separation with improved selectivity and permeability. Polymetric membranes for gas separation are rapidly developing with growing interest.

As Received Condition: As-received film

Analyzed Region: 200 × 200 μm2

Ex Situ Preparation/Mounting: ∼8 × 8 mm2 membrane piece was cut from the membrane film and stabilized on a back-mount holder.

In Situ Preparation: N/A

Charge Control Conditions and Procedures: Low-energy electrons

Temp. During Analysis: 298 K

Pressure During Analysis: 1.1 × 10−6 Pa

Pre-analysis Beam Exposure: N/A

Manufacturer and Model: IONTOF TOF-SIMS 5

Analyzer Type: Time-of-flight

Sample Rotation: No

Rotation Rate: N/A

Oxygen Flood Source: N/A

Oxygen Flood Pressure: N/A

Other Flood Source: N/A

Other Flood Pressure: N/A

Unique Instrument Features Used: N/A

Energy Acceptance Window: 20 eV

Post-acceleration Voltage: 10 000 eV

Sample Bias: 0 eV

Specimen Normal-to-analyzer (Θe): 90°

Ion source 1 of Bi3++

Purpose of this Ion Source: Analysis beam

Ion Source Manufacturer: IONTOF (Münster, Germany)

Ion Source Model: Bin+ cluster ion source

Beam Mass Filter: Yes

Beam Species and Charge State: Bi3++

Beam Gating Used: No

Additional Beam Comments: N/A

Beam Voltage: 50 000 eV

Net Beam Voltage (impact voltage): 50 000 eV

Ion Pulse Width: 0.8–1.0 ns

Ion Pulse Rate: 10.0 kHz

DC Beam Current: 14 nA

Pulsed Beam Current: 0.0002 nA

Current Measurement Method: Faraday cup

Beam Diameter: 5 μm

Beam Raster Size: 200 × 200 μm2

Raster Pixel Dimensions: 128 × 128

Beam Incident Angle: 45°

Source-to-Analyzer Angle: 45°

Ion source 2 of Ar cluster

Purpose of this Ion Source: Sputtering beam

Ion Source Manufacturer: IONTOF (Münster, Germany)

Ion Source Model: Ar cluster ion source

Beam Mass Filter: Yes

Beam Species and Charge State: Ar+

Beam Gating Used: No

Additional Beam Comments: For removing potential surface contamination

Beam Voltage: 10 000 eV

Net Beam Voltage (impact voltage): 10 000 eV

Ion Pulse Width: 30 000 ns

Ion Pulse Rate: 10 kHz

DC Beam Current: 12 nA

Pulsed Beam Current: 5.1 nA

Current Measurement Method: Faraday cup

Beam Diameter: 20 μm

Beam Raster Size: 1000 × 1000 μm2

Raster Pixel Dimensions: 128 × 128

Beam Incident Angle: 45°

Source-to-Analyzer Angle: 45°

SPECTRAL FEATURES TABLE

Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01886-01 55.056 (28.3) C4H7+ PEEK-ionene backbone fragment 
 82.055 (33.2) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.064 (42.3) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 95.061 (2.9) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 96.070 (19.5) C5H8N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 109.077 (4.1) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 123.097 (45.0) C7H11N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 137.111 (24.1) C8H13N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 151.123 (−3.0) C9H15N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 165.138 (−6.3) C10H17N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 205.166 (−20.1) C13H21N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 219.180 (−26.8) C14H23N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 233.195 (−27.0) C15H25N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 247.206 (−42.3) C16H27N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 329.261 (−28.0) C20H33N4+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 692.237 (−51.9) C28H44F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazoliumand Tf2N fragments {[C10H17N2] [CF3SO2NSO2CF3] [C16H27N2]}+ 
Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01886-01 55.056 (28.3) C4H7+ PEEK-ionene backbone fragment 
 82.055 (33.2) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.064 (42.3) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 95.061 (2.9) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 96.070 (19.5) C5H8N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 109.077 (4.1) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 123.097 (45.0) C7H11N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 137.111 (24.1) C8H13N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 151.123 (−3.0) C9H15N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 165.138 (−6.3) C10H17N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 205.166 (−20.1) C13H21N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 219.180 (−26.8) C14H23N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 233.195 (−27.0) C15H25N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 247.206 (−42.3) C16H27N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 329.261 (−28.0) C20H33N4+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 692.237 (−51.9) C28H44F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazoliumand Tf2N fragments {[C10H17N2] [CF3SO2NSO2CF3] [C16H27N2]}+ 

Accession #: 01886-01 
■ Specimen: Synthesized PEEK-ionene sample No. 1 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 7254 m/Δm 
Mass Resolution Determined at: 29.040 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #: 01886-01 
■ Specimen: Synthesized PEEK-ionene sample No. 1 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 7254 m/Δm 
Mass Resolution Determined at: 29.040 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Accession #: 01886-01 
■ Specimen: Synthesized PEEK-ionene sample No. 1 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 7254 m/Δm 
Mass Resolution Determined at: 29.040 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #: 01886-01 
■ Specimen: Synthesized PEEK-ionene sample No. 1 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 7254 m/Δm 
Mass Resolution Determined at: 29.040 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Close modal

SPECTRAL FEATURES TABLE

Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01887-01 55.057 (56.3) C4H7+ PEEK-ionene backbone fragment 
 82.056 (43.1) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.065 (52.8) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 91.059 (46.4) C7H7+ Xylene fragment from PEEK-ionene backbone 
 95.066 (49.1) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 96.070 (15.4) C5H8N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 104.069 (61.4) C8H8+ Xylene fragment from PEEK-ionene backbone 
 105.075 (44.7) C8H9+ Xylene fragment from PEEK-ionene backbone 
 109.079 (29.5) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 213.056 (−58.0) C7H11N5OS+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragments{[C4H6N2] [NSO] [C3H5N2]}+ 
 247.207 (−39.2) C16H27N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 535.266 (56.4) C27H34F3N4O2S+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragment {[C26H34N4] [CF3SO2]}+ 
 631.209 (58.3) C24H31F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion{[C22H31N4] [CF3SO2NSO2CF3]}+ 
 713.264 (19.1) C30H41F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion {[C28H41N4] [CF3SO2NSO2CF3]}+ 
Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01887-01 55.057 (56.3) C4H7+ PEEK-ionene backbone fragment 
 82.056 (43.1) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.065 (52.8) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 91.059 (46.4) C7H7+ Xylene fragment from PEEK-ionene backbone 
 95.066 (49.1) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 96.070 (15.4) C5H8N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 104.069 (61.4) C8H8+ Xylene fragment from PEEK-ionene backbone 
 105.075 (44.7) C8H9+ Xylene fragment from PEEK-ionene backbone 
 109.079 (29.5) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 213.056 (−58.0) C7H11N5OS+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragments{[C4H6N2] [NSO] [C3H5N2]}+ 
 247.207 (−39.2) C16H27N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 535.266 (56.4) C27H34F3N4O2S+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragment {[C26H34N4] [CF3SO2]}+ 
 631.209 (58.3) C24H31F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion{[C22H31N4] [CF3SO2NSO2CF3]}+ 
 713.264 (19.1) C30H41F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion {[C28H41N4] [CF3SO2NSO2CF3]}+ 

Accession #:01887-01
■ Specimen: Synthesized PEEK-ionene sample No. 2 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4235 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #:01887-01
■ Specimen: Synthesized PEEK-ionene sample No. 2 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4235 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Accession #:01887-01
■ Specimen: Synthesized PEEK-ionene sample No. 2 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4235 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #:01887-01
■ Specimen: Synthesized PEEK-ionene sample No. 2 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4235 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Close modal

SPECTRAL FEATURES TABLE

Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01888-01 55.055 (4.9) C4H7+ PEEK-ionene backbone fragment 
 82.057 (54.4) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.065 (57.2) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 91.059 (47.9) C7H7+ Xylene fragment from PEEK-ionene backbone 
 95.065 (43.7) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 104.069 (63.5) C8H8+ Xylene fragment from PEEK-ionene backbone 
 105.076 (51.3) C8H9+ Xylene fragment from PEEK-ionene backbone 
 109.080 (38.4) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 213.050 (−32.3) C7H11N5OS+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragments{[C4H6N2] [NSO] [C3H5N2]}+ 
 631.160 (−19.0) C24H31F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion {[C22H31N4] [CF3SO2NSO2CF3]}+ 
Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01888-01 55.055 (4.9) C4H7+ PEEK-ionene backbone fragment 
 82.057 (54.4) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.065 (57.2) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 91.059 (47.9) C7H7+ Xylene fragment from PEEK-ionene backbone 
 95.065 (43.7) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 104.069 (63.5) C8H8+ Xylene fragment from PEEK-ionene backbone 
 105.076 (51.3) C8H9+ Xylene fragment from PEEK-ionene backbone 
 109.080 (38.4) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 213.050 (−32.3) C7H11N5OS+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragments{[C4H6N2] [NSO] [C3H5N2]}+ 
 631.160 (−19.0) C24H31F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion {[C22H31N4] [CF3SO2NSO2CF3]}+ 

Accession #: 01888-01 
■ Specimen: Synthesized PEEK-ionene sample No. 3 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4416 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 25 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #: 01888-01 
■ Specimen: Synthesized PEEK-ionene sample No. 3 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4416 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 25 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Accession #: 01888-01 
■ Specimen: Synthesized PEEK-ionene sample No. 3 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4416 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 25 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #: 01888-01 
■ Specimen: Synthesized PEEK-ionene sample No. 3 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4416 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 25 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Close modal

SPECTRAL FEATURES TABLE

Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01889-01 55.056 (27.6) C4H7+ PEEK-ionene backbone fragment 
 82.056 (46.0) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.065 (58.1) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 95.061 (0.0) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 96.063 (28.8) C5H8N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 109.079 (24.7) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 123.099 (61.8) C7H11N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 137.114 (50.1) C8H13N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 151.130 (43.5) C9H15N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 165.144 (34.0) C10H17N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 276.092 (58.2) C10H17FN4O2S+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragments { [C4H7N2] [SO2F] [C6H10N2]}+ 
 369.144 (55.6) C23H17N2O3+ PEEK-ionene backbone fragment (EEK)(2mIm) Fig. 1(d)  
 581.184 (48.0) C20H29F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion{[C18H29N4][CF3SO2NSO2CF3]}+ 
Spectrum ID #Mass (Δm), DaSpeciesPeak Assignment
01889-01 55.056 (27.6) C4H7+ PEEK-ionene backbone fragment 
 82.056 (46.0) C4H6N2+ Deprotonated 2-methylimidazolium from PEEK-ionene backbone 
 83.065 (58.1) C4H7N2+ 2-methylimidazolium from PEEK-ionene backbone 
 95.061 (0.0) C5H7N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 96.063 (28.8) C5H8N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 109.079 (24.7) C6H9N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 123.099 (61.8) C7H11N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 137.114 (50.1) C8H13N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 151.130 (43.5) C9H15N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 165.144 (34.0) C10H17N2+ Alkyl-2-methylimidazolium from PEEK-ionene backbone 
 276.092 (58.2) C10H17FN4O2S+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N fragments { [C4H7N2] [SO2F] [C6H10N2]}+ 
 369.144 (55.6) C23H17N2O3+ PEEK-ionene backbone fragment (EEK)(2mIm) Fig. 1(d)  
 581.184 (48.0) C20H29F6N5O4S2+ Cluster ion containing alkyl-2-methylimidazolium and Tf2N anion{[C18H29N4][CF3SO2NSO2CF3]}+ 

Accession #: 01889-01 
■ Specimen: Synthesized PEEK-ionene sample No. 4 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4070 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #: 01889-01 
■ Specimen: Synthesized PEEK-ionene sample No. 4 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4070 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Accession #: 01889-01 
■ Specimen: Synthesized PEEK-ionene sample No. 4 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4070 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 
Accession #: 01889-01 
■ Specimen: Synthesized PEEK-ionene sample No. 4 
■ Technique: SIMS 
Instrument: IONTOF TOF-SIMS 5 
Analyzer Type: Time-of-flight 
Analyzer Mass Resolution: 4070 m/Δm 
Mass Resolution Determined at: 29.041 (C2H5+) Da 
Species Used for Mass Calibration: CH3+, C2H5N+, SO+, C4H5+, and C6H8N2+ 
Specimen Normal-to-Analyzer: 0° 
Source-to-Analyzer Angle: 45° 
Primary Beam Ion Gun: Bi liquid metal ion gun 
Primary Ion Species: Bi3++ 
Primary Ion Dose: 2.5 × 1011 ion/cm2 
Primary Ion Pulse Width: 0.8–1.0 ns 
Primary Ion Pulse Rate: 10.0 kHz 
Net Beam Voltage: 50 000 eV 
Pulsed Beam Current: 0.0002 nA 
DC Beam Current: 14 nA 
Beam Diameter: 5 μ
Beam Raster Size: 200 × 200 μm2 
Beam Incident Angle: 45° 
Secondary Source Polarity: Positive 
Mass Range Minimum: 0 Da 
Mass Range Maximum: 850 Da 
Spectrum Dead Time Corrected: Yes 
Total Spectral Acquisition Time: 200 s 
Comment: Data were not binned prior to plotting 

Close modal

This work, associated with direct air capture (DAC) of CO2 project, was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Materials Science and Separation Science program, No. FWP 76830.

The authors have no conflicts to disclose.

Lyndi E. Strange: Writing – original draft (equal). David J. Heldebrant: Funding acquisition (equal); Project administration (equal); Supervision (equal); Writing – review & editing (equal). Sudhir Ravula: Investigation (equal); Resources (equal); Writing – review & editing (equal). Ping Chen: Writing – review & editing (equal). Zihua Zhu: Writing – review & editing (equal). Jason E. Bara: Methodology (equal); Resources (equal); Writing – review & editing (equal). Jennifer Yao: Supervision (equal); Writing – original draft (equal); Writing – review & editing (equal).

The data that support the findings of this study are available within the article and its supplementary material.

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Supplementary Material