X-ray powder diffraction study of polytetrafluoroethylene

Lebedev, Yu. A.; Korolev, Yu. M.; Поликарпов, В. М.; Игнатьева, Л. Н.; Антипов, Е. М.

doi:10.1134/s1063774510040127

Cited by 46 publications

(35 citation statements)

References 1 publication

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“…To identify the phase of Cu catalysts, X-ray diffraction (XRD) measurements were conducted. The XRD patterns ( Figure S4) show the PTFE 39 and carbon peaks derived from GDE substrates as well as the (111), (200), and (211) Cu peaks with the dominant (111) peak.…”

Section: Fabrication and Characterization Of Cu Catalystsmentioning

confidence: 99%

Insights into the carbon balance for CO₂ electroreduction on Cu using gas diffusion electrode reactor designs

Clark

Therkildsen

et al. 2020

Energy Environ. Sci.

367

429

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Section: Fabrication and Characterization Of Cu Catalystsmentioning

confidence: 99%

Insights into the carbon balance for CO₂ electroreduction on Cu using gas diffusion electrode reactor designs

Clark

Therkildsen

et al. 2020

Energy Environ. Sci.

367

429

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“…It is evident that the two signals of the amorphous PF‐initiator observed at 2θ ~ 18° and weakly at 40° (Supporting Information S12) appear also in the block copolymer. Russel et al 54 also observed a broadened peak at 2θ ~ 18° for perfluorinated segments when an alkyl sequence (CH 2 ) m with m ≥ 16 was attached, which can be interpreted as an 2D‐pseudohexagonal mesomorphic phase 55 . As no melting peak in DSC measurements was found, it can be argued that the PF segments phase separate in block copolymer by forming not well‐ordered, amorphous domains.…”

Section: Resultsmentioning

confidence: 99%

“…Russel et al 54 also observed a broadened peak at 2θ $ 18 for perfluorinated segments when an alkyl sequence (CH 2 ) m with m ≥ 16 was attached, which can be interpreted as an 2D-pseudohexagonal mesomorphic phase. 55 As no melting peak in DSC measurements was found, it can be argued that the PF segments phase separate in block copolymer by forming not well-ordered, amorphous domains. This could be attributed to the fact that the PF segments after connecting to block copolymer chains at both ends lose their chain-end mobility that is required for placement of the chain in the regular crystal lattice.…”

Section: Synthesis and Characterization Of Triphilic Ppo-b-pgma-b-pmentioning

confidence: 99%

Triphilic pentablock copolymers with perfluoroalkyl segment in central position

Heinz

Meister

Hussain

et al. 2020

Journal of Polymer Science

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Adding perfluoroalkyl (PF) segments to amphiphilic copolymers yields triphilic copolymers with new application profiles. Usually, PF segments are attached as terminal blocks via Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC). The purpose of the current study is to design new triphilic architectures with a PF segment in central position. The PF segment bearing bifunctional atom transfer radical polymerization (ATRP) initiator is employed for the fabrication of triphilic poly(propylene oxide)-b-poly(glycerol monomethacrylate)b-PF-b-poly(glycerol monomethacrylate)-b-poly(propylene oxide) PPO-b-PGMA-b-PF-b-PGMA-b-PPO pentablock copolymers by a combined ATRP and CuAAC reaction approach. Differential scanning calorimetry indicates the PF-initiator to undergo a solid-solid phase transition at 63 C before the final crystal melting at 95 C. This is further corroborated by polarized optical microscopy and X-ray diffraction studies. The PF-initiator could successfully polymerize solketal methacrylate (SMA) under typical ATRP conditions producing well-defined Br-PSMA-b-PF-b-PSMA-Br triblock copolymers that are then converted into PPO-b-PSMA-b-PF-b-PSMA-b-PPO pentablock copolymer via CuAAC reaction. Subsequently, acid hydrolysis of the PSMA blocks afforded water soluble well-defined triphilic pentablock copolymers PPO-b-PGMA-b-PF-b-PGMA-b-PPO with fluorophilic central segment, hydrophilic middle blocks, and lipophilic outer blocks. The triphilic block copolymers could self-assemble, depending upon the preparatory protocol, into spherical and filament-like phase-separated nanostructures as revealed by transmission electron microscopy.

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“…The diffraction patterns of the initial and TRM-PTFE were indexed by the method described in [14][15][16], taking into account the reference data (protocol JCPDS No. 47-2217 [17]) and the results previously obtained in [18][19][20]. The procedure for determining the degree of crystallinity X c of polymers was described earlier [11].…”

Section: Characterization Of X-ray Diffraction Patterns Registered For Initial and Thermal-radiation Modified Polytetrafluoroethylenementioning

confidence: 97%

“…It is usually considered that PTFE crystals at room temperature belong to the hexagonal system with the unit cell containing 15 CF 2 groups packed into a spiral with 7 turns around the hexagonal axis [14][15][16][17][18][19][20]. Gamma-irradiation of PTFE up to 173 kGy with simultaneous exposure to temperatures in the range of 327-350°С leads to the shift of almost all diffraction maxima towards smaller diffraction angles (Table 1).…”

Section: Characterization Of X-ray Diffraction Patterns Registered For Initial and Thermal-radiation Modified Polytetrafluoroethylenementioning

confidence: 99%

Structure of polytetrafluoroethylene modified by the combined action of γ-radiation and high temperatures

Smolyanskiĭ¹,

Политова²,

Koshkina³

et al. 2021

Preprint

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By means of X-ray computed microtomography (XCMT) the existence of a developed microporous structure having an average pore diameter of ~3.5 μm and pore content of ~1.1 vol.% has been revealed in unirradiated polytetrafluoroethylene (PTFE). It has been found that the combined action of gamma radiation (absorbed dose per PTFE of ~170 kGy) and high temperatures (327-350 °C) leads to the disappearance of the microporous structure and the formation of several large pores with sizes from 30 to 50 μm in the bulk of thermal-radiation modified PTFE (TRM-PTFE). It has been established by X-ray diffraction (XRD) analysis that the thermal-radiation modification of PTFE leads to an increase in the interplanar spacings, the degree of crystallinity and volume of the unit cell, as well as to a decrease in the size of crystals and the X-ray density of the crystalline phase in comparison with the initial polymer. It is assumed that the previously established effect of improving the deformation-strength and tribological properties of the TRM-PTFE can be due not only to the radiation cross-linking of polymer chains but also to the disappearance of the micropore system and to the ordering of the crystalline phase of PTFE.

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X-ray powder diffraction study of polytetrafluoroethylene

Cited by 46 publications

References 1 publication

Insights into the carbon balance for CO₂ electroreduction on Cu using gas diffusion electrode reactor designs

Insights into the carbon balance for CO₂ electroreduction on Cu using gas diffusion electrode reactor designs

Triphilic pentablock copolymers with perfluoroalkyl segment in central position

Structure of polytetrafluoroethylene modified by the combined action of γ-radiation and high temperatures

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X-ray powder diffraction study of polytetrafluoroethylene

Cited by 46 publications

References 1 publication

Insights into the carbon balance for CO2 electroreduction on Cu using gas diffusion electrode reactor designs

Insights into the carbon balance for CO2 electroreduction on Cu using gas diffusion electrode reactor designs

Triphilic pentablock copolymers with perfluoroalkyl segment in central position

Structure of polytetrafluoroethylene modified by the combined action of γ-radiation and high temperatures

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Insights into the carbon balance for CO₂ electroreduction on Cu using gas diffusion electrode reactor designs

Insights into the carbon balance for CO₂ electroreduction on Cu using gas diffusion electrode reactor designs