Acid Fluoride Groups Research Articles

The investigation of the structural change and the wetting behavior of electron beam irradiated PTFE film

AbstractThe effect of electron beam (EB) irradiation on polytetrafluoroethylene (PTFE) film was studied in air at room temperature. The structural changes of the PTFE film irradiated by EB were determined by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). The morphological changes on the film surface were described using scanning electron microscopy (SEM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. The results show that scission of the chain on the surface of PTFE film was induced by EB irradiation. The atomic ratio of F/C decreased and the atomic ratio of O/C increased. The surface roughness of the irradiated sample increased. In the case of irradiation in the presence of residual air, carboxylic acid fluoride groups appear and can hydrolyze to carboxylic groups in the surface-near regions. These polar groups significantly reduced the hydrophobicity and oleophobicity of the PTFE film and consequently cause the decline of the water contact angle of the film surface. XRD analysis reveals an increase of the crystallite size of PTFE along with the increasing time of the irradiate.

The effect of electron irradiation on the tribological property of perfluoropolyether grease in vacuum

Abstract A perfluoropolyether (PFPE) grease was exposed to 110 keV electron beam for fluence of 1 × 1015, 5 × 1015 and 1 × 1016 e/cm2 in vacuum. The friction and wear behaviour of the electron irradiated grease-lubricated 2Cr13 steel in vacuum was investigated by using a pin-on-disk type tribometer. The morphologies of the worn surfaces for the irradiated grease-lubricated 2Cr13 steel were observed by a scanning electron microscope (SEM). Gaseous products from the PFPE grease during the electron irradiation were monitored with a quadrupole mass spectrometer (QMS). The compositions and chemical states of grease samples before and after electron irradiation were analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results show that the irradiated grease-lubricated 2Cr13 steel sliding against the same material in vacuum presents a high friction and a high wear. The QMS, XPS and FTIR analyses reveal that COF2 gas, low molecular weight perfluoroethers and acid fluoride groups are formed due to decomposition when the PFPE grease is exposed to 110 keV electron beam in vacuum. Moreover, the base oil content of the PFPE grease decreases with increasing the electron irradiation fluence, leading to the loss of lubricating ability of the PFPE grease.

Micro‐ and Nanopatterning of Functional Organic Monolayers on Oxide‐Free Silicon by Laser‐Induced Photothermal Desorption

The photothermal laser patterning of functional organic monolayers, prepared on oxide-free hydrogen-terminated silicon, and subsequent backfilling of the laser-written lines with a second organic monolayer that differs in its terminal functionality, is described. Since the thermal monolayer decomposition process is highly nonlinear in the applied laser power density, subwavelength patterning of the organic monolayers is feasible. After photothermal laser patterning of hexadecenyl monolayers, the lines freed up by the laser are backfilled with functional acid fluoride monolayers. Coupling of cysteamine to the acid fluoride groups and subsequent attachment of Au nanoparticles allows easy characterization of the functional lines by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Depending on the laser power and writing speed, functional lines with widths between 1.1 μm and 250 nm can be created. In addition, trifluoroethyl-terminated (TFE) monolayers are also patterned. Subsequently, the decomposed lines are backfilled with a nonfunctional hexadecenyl monolayer, the TFE stripes are converted into thiol stripes, and then finally covered with Au nanoparticles. By reducing the lateral distance between the laser lines, Au-nanoparticle stripes with widths close to 100 nm are obtained. Finally, in view of the great potential of this type of monolayer in the field of biosensing, the ease of fabricating biofunctional patterns is demonstrated by covalent binding of fluorescently labeled oligo-DNA to acid-fluoride-backfilled laser lines, which--as shown by fluorescence microscopy--is accessible for hybridization.

Microcontact Printing onto Oxide‐Free Silicon via Highly Reactive Acid Fluoride‐Functionalized Monolayers

This work describes a new route for patterning organic monolayers on oxide-free silicon by microcontact printing (microCP) on a preformed, reactive, acid-fluoride-terminated monolayer. This indirect printing approach is fast and easily preserves the oxide-free and well-defined monolayer-silicon interface, which is the most important property for potential applications in biosensing and molecular electronics. Water-contact-angle measurements, ellipsometry, attenuated total reflection infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) demonstrate the formation of the initial acid-fluoride-terminated monolayers without upside-down attachment. Subsequent printing for twenty seconds with an N-hexadecylamine-inked poly(dimethylsiloxane) stamp results in well-defined 5-microm N-hexadecylamide dots, as evidenced by atomic force microscopy and scanning electron microscopy. Printing with a flat stamp allows investigation of the efficiency of amide formation by microCP and water-contact-angle measurements, ellipsometry, and XPS reveal the quantitative conversion of the acid fluoride groups to the corresponding amide within twenty seconds. The absence of silicon oxide, even after immersion in water for 16 h, demonstrates that the oxide-free monolayer-silicon interface is easily preserved by this patterning route. Finally, it is shown by fluorescence microscopy that complex biomolecules, like functionalized oligo-DNA, can also be immobilized on the oxide-free silicon surface via microCP.

Modification of fluoropolymers by means of electron beam irradiation

Abstract High molecular weight polytetrafluoroethylene (PTFE) is transformed to free-flowing micropowder by treatment with electron beams. In case of irradiation in presence of air carboxylic acid fluoride groups are incorporated which rapidly hydrolyze to carboxylic groups in the surface-near regions due to atmospheric humidity. These polar groups reduce the hydrophobic and oleophobic properties so much that homogeneous compounding with other materials becomes possible. In addition to PTFE, copolymers of tetrafluoroethylene with hexafluoropropylene (FEP) and perfluoropropylvinylether (PFA) were modified. In case of identical irradiation conditions, the concentration of carboxylic groups is much higher in FEP and PFA than in PTFE, which is due to the lower crystallinity of the copolymers. Electron beam irradiation of PTFE was performed in vacuum at elevated temperature above the melting point. The changes in the chemical structure were studied. The concentration of CF3 branches was found to be much higher as compared to room temperature irradiation. In a practical test PTFE micropowders functionalized by electron irradiation were compounded with epoxy resins, with polyoximethylene and with polyamides. Such compounds are characterized by very good frictional and wearing behaviour in dry-running tests.

The synthesis of functionalised perfluorocyclohexanes by the liquid phase fluorination of fluoroaromatics with elemental fluorine

The fluorosulphonyl perfluorocyclohexane carbonyl fluorides 1,4 FOC·C 6F 10·SO 2F(I) and 1,2 FOC·C 6F 10·SO 2F(II) have been synthesised [1] by direct fluorination of respectively 1,4 FOC·C 6F 4·SO 2F(III) and 1,2 FOC·C 6F 4·S0 2F(IV). The use of elemental fluorine for the fluorination of aromatic compounds is usually unsuccessful, even under very carefully controlled conditions, producing mainly oligomers and polymeric tars [2]. However, fluorination of 1,4 FOC·C 6F 4·SO 2F(III) [1,3] in CCl 2F·CClF 2 with F 2/N 2 at ambient temperatures gave 1,4 FCO·C 6F 10·SO 2F(I), together with C 6F 11·COF(V) and oligomers. ▪ This novel difunctional perfluorocyclohexane has been characterised by reaction with alcohols and amines, where the different reactivities of the acid fluoride groups allows derivatives to be prepared on the carbonyl fluoride, leaving the sulphonyl fluoride intact.

ChemInform Abstract: Irradiation of Poly(perfluoropropylene Oxide) by a 175 kV Electron Beam: The Formation and Hydrolysis of Acid Fluoride Groups.

Chemischer InformationsdienstVolume 17, Issue 52 Preparative Organic Chemistry ChemInform Abstract: Irradiation of Poly(perfluoropropylene Oxide) by a 175 kV Electron Beam: The Formation and Hydrolysis of Acid Fluoride Groups. J. PACANSKY, J. PACANSKYSearch for more papers by this authorR. J. WALTMANN, R. J. WALTMANNSearch for more papers by this authorC. WANG, C. WANGSearch for more papers by this author J. PACANSKY, J. PACANSKYSearch for more papers by this authorR. J. WALTMANN, R. J. WALTMANNSearch for more papers by this authorC. WANG, C. WANGSearch for more papers by this author First published: December 30, 1986 https://doi.org/10.1002/chin.198652122AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue52December 30, 1986 RelatedInformation

Irradiation of poly(perfluoropropylene oxide) by a 175 KV electron beam: The formation and hydrolysis of acid fluoride groups

Poly(perfluoropropylene oxide), −(CF(CF3)CF2O)n−, was exposed to a 175kV electron beam while under a blanket of N2 at atmospheric pressure. The electron beam induced chemistry was spectroscopically analyzed using infrared techniques. The IR analysis revealed that acid fluoride groups were formed by the electron beam exposure which rapidly hydrolyzed to form a car☐ylic acid and HF. Viscosity studies on the irradiated material show that the net effect of the electron beam exposure is to initially reduce the viscosity; when the irradiated material is exposed to air the viscosity increases as a function of the time in contact with the atmosphere. These latter viscosity changes are attributed to the hydrolysis reaction.

The addition of tetrafluoroethylene oxide to [formula omitted]-glutaryl fluoride [1]. Relative reactivities of acid fluorides [2

Data obtained from the addition of tetrafluoroethylene oxide to F -glutaryl fluoride show significant differences to exist between the relative reactivities of the acid fluoride groups involved. The order of reactivity is F -glutaryl fluoride > -OCF 2COF > -CF 2CF 2COF.

Reactions and wetting properties of 1:1 perfluoroalkyl allyl and methallyl ether–maleic anhydride copolymers

AbstractPolymers with fluoroalkyl side‐groups on three of every four carbon atoms along the polymer main chain were made by treating 1 : 1 copolymers of perfluoroallyl (or methallyl)ethers and maleic anhydride with SF4, and then esterifying the resulting acid fluoride groups with 1H, 1H‐pentadecafluorooctanol. Surface wettability of these polymers by polar and non‐polar liquids was studied. The critical surface tension (γc) was found by Zisman's method. The dispersion force component of polymer surface energy (γsD) and the polar component of surface energy (γsp) were calculated by the respective methods of Fowkes and Owens. The γc values for several of the highly fluorinated polymers were lower than previously reported for any fluoropolymer but not so low as has been observed for the surface of an oriented perfluoroacid monolayer. In the range 11.4–18.5 dyne/cm, γc approximates γsD for the fluorinated surfaces; however at lower γc values, considerable difference between γc and γsD was noted.