摘要:

A sample of 1,1-dihydroperfluorooctyl acrylate (PFOA), a low surface energy polymeric material prepared by homogeneous free radical solution polymerization in supercritical CO2, has been investigated by x-ray photoelectron spectroscopy (XPS) using a Perkin-Elmer Physical Electronics Model 5400 spectrometer with monochromatic AlKαx rays. Knowledge of the surface composition of PFOA is significant since potential applications of this homopolymer include use in polymer blends where this material would be expected to be the surface active species. Controlled surface studies were conducted on a thick polymer film (∼0.5μm) spun cast from solution onto silicon. Although the F 1sand O 1sregions were structurally straightforward to interpret, the C 1swindow showed the expected pattern of functional group components.

ISSN:1055-5269    

DOI:10.1116/1.1247742

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A sample of 1,1-dihydroperfluorooctyl methacrylate (PFOMA), a low surface energy polymeric material prepared by homogeneous free radical solution polymerization in supercritical CO2, has been investigated by x-ray photoelectron spectroscopy (XPS) using a Perkin-Elmer Physical Electronics Model 5400 spectrometer with monochromatic AlKαx rays. Knowledge of the surface composition of PFOMA is significant since potential applications of this homopolymer include use in polymer blends where this material would be expected to be the surface active species. Controlled surface studies were conducted on a thick polymer film (∼0.5μm) spun cast from solution onto silicon. Although the F 1sand O 1sregions were structurally straightforward to interpret, the C 1swindow showed the expected pattern of functional group components.

ISSN:1055-5269    

DOI:10.1116/1.1247743

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A sample of 1,1,2,2-tetrahydroperfluorooctyl acrylate (PTAN), a low surface energy polymeric material prepared by homogeneous free radical solution polymerization in supercritical CO2, has been investigated by x-ray photoelectron spectroscopy (XPS) using a Perkin-Elmer Physical Electronics Model 5400 spectrometer with monochromatic AlKαx rays. Knowledge of the surface composition of PTAN is significant since potential applications of this homopolymer include use in polymer blends where this material would be expected to be the surface active species. Controlled surface studies were conducted on a thick polymer film (∼0.5μm) spun cast from solution onto silicon. Although the F 1sand O 1sregions were structurally straightforward to interpret, the C 1swindow showed the expected pattern of functional group components.

ISSN:1055-5269    

DOI:10.1116/1.1247786

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The C 1sphotoelectron spectra are compared for the aliphatic hydrocarbons, hexatriacontane and polyethylene. An asymmetric C 1senvelope is observed regardless of sample form.

ISSN:1055-5269    

DOI:10.1116/1.1247761

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Poly(ethylene terephthalate) is used in numerous industrial applications. Successful medical applications are in the area of cardiovascular surgery. Its chemical functionality makes it propitious to grafting biochemical compounds; surface modification by plasma treatment may also be used to improve biocompatibility and modify wetting properties. The analyzed specimen was a commercial film (Mylar A). The main C 1sregion was decomposed into three main components which were clearly identified on the recorded spectrum: 284.8, 286.4, and 288.8 eV attributed, respectively, to carbon only bound to carbon and hydrogen [C_—(C,H)], carbon making a single bond with oxygen[C_—O] and carbon of ester [C_OO]. Satellite peaks were found at 291.3, 293.5, and 295.8 eV. The molar ratiosC_—(C,H):C_—O:C_OO were 3:0.92:0.91 excluding the satellite peaks, to be compared with the expected values of 3:1:1. The O 1speak showed two partially resolved components at 531.6[O_=C—O] and 533.3 eV [O=C—O_] with a satellite at 538.2 eV. The O:C ratio was 27.8:72.2, to be compared with the expected values of 28.6:71.4. The FWHM of the main C 1scomponents was in the range of 0.90 to 1.23 eV depending on the component and the mode of decomposition; the FWHM of O 1scomponents was about 1.40 eV.

ISSN:1055-5269    

DOI:10.1116/1.1247762

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Poly(L-serine) was analyzed as a model compound representative of poly(amino acids) with uncharged polar pendant groups. The sample powder was pressed on an indium foil to obtain a relatively smooth surface. The C 1speak was recorded first, and recorded again at the end; no difference was found between the two records, indicating that poly(L-serine) did not suffer beam damage. The C 1speak was split in four components. The [O=C_—N] component, characteristic of amide, was fixed at 288.0 eV; a component found at 286.2 eV was attributed to [C_—N] and [C_—OH]. The ratio ([C_—N]+[C_—OH])/[O=C_—N] was 1.85, while the stoichiometric value is 2.00. Two additional peaks were found: one set at 284.8 eV attributed to [C_—(C;H)] of contaminants and one at 289.1 eV attributed to [O=C_—OH] of chain ends and possible contaminants. The O 1speak was split into two components at 531.4 and 532.6 eV attributed to [O_=C—N] and [C—O_H], respectively, which were not resolved. The ratio between the two peaks ([O_—C]/[C=O_—N=0.95) was close to the stoichiometric value of 1. The N 1speak at 399.8 eV attributed to the amide nitrogen appeared with a small tail reflecting the presence of traces of protonated nitrogen. The overall N:O:C atomic ratios were 0.30:0.61:1.00 to be compared with the expected value of 0.33:0.66:1.00. These spectra could be used as references for the characterization of polypeptides and proteins.

ISSN:1055-5269    

DOI:10.1116/1.1247763

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Poly(L-leucine) was analyzed as a model compound representative of poly(amino acids) with alkyl pendant groups. Two specimens of different origins and molecular masses were examined. One (A) was pressed on an indium foil to allow recording time of flight secondary ion mass spectrometry (TOF SIMS) spectra in parallel and, therefore, insure good electrical charge dissipation. The other one (B) was placed in a stainless steel trough and then pressed. The C 1speak was recorded first and recorded again at the end; no difference was found between the two records, indicating that poly(L-leucine) did not suffer beam damage. The C 1speak of specimen A was split into three components: one fixed at 284.8 eV and due toC_—(C,H), the other two found at 286.1 and 287.8 eV and due toC_—N andO=C_—N, respectively. The O 1speak centered at 531.2 eV and due toO_=C—N showed a tail which indicated the presence of a small component at 533.0 eV, possibly due to water orC—O_H of contaminating compounds. The N 1speak was symmetric and centered at 399.7 eV. The position of the peak components of specimen B were coincident with specimen A within 0.1 eV. The ratio of the molar concentration, with respect to N, of[O_=C—N], [O=C_—N], and[C_—N], on the one hand, and of[C_—(C,H)], on the other hand, fitted the expected values of 1 and 4 within 5%, except for one component of one specimen which showed a deviation of 15%. The choice of the background shape (S shape or linear) has no significant influence on the results. These spectra may be used as references for the characterization of polypeptides and proteins.

ISSN:1055-5269    

DOI:10.1116/1.1247787

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

High resolution x-ray photoelectron spectra (XPS) are reported for poly(ethylene terephthalate) (PET) in the form of biaxially oriented crystalline film and amorphous polymer melt (i.e., molten inside the spectrometer during analysis). A small(∼0.14 eV) but unambiguous shift of the C 1sglycol component, relative to the aromatic and carboxyl components, is observed on going from crystalline film to amorphous polymer melt. It is known from x-ray diffraction data and infrared spectroscopy that the crystalline to amorphous transition is accompanied by a change fromtranstogaucheconformation of the glycol unit of the polymer repeat unit, and we ascribe the observed C 1sglycol shift to the same effect. Small differences between crystalline and amorphous PET are also observed in the valence band. Under the conditions of the XPS analysis the polymer melt appears to be electrically conducting.

ISSN:1055-5269    

DOI:10.1116/1.1247788

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Under the conditions of x-ray photoelectron spectra (XPS) analysis organic liquids appear to behave as electrical conductors. Here we report x-ray photoelectron spectra for pentaphenylether and pentaphenyltrimethyltrisiloxane oils at room temperature. These materials are commercially available as diffusion pump fluids (Santovac 5 and DC705, respectively). Their room temperature vapor pressures are ∼2 × 10−8Pa and they can be studied by XPS without hazard to the spectrometer vacuum system. Both materials were investigated as relatively thick liquid films (∼10μm, as determined by weighing) on a piece of silicon wafer. A solid organic film of this thickness would be expected to be an XPS insulator. The oil films on silicon required no external charge compensation and gave high resolution C 1sspectra with the first component of the envelope very close to 285 eV binding energy. Measured binding energies closely followed a bias voltage applied to the silicon wafer. Oil films thicker than 10μm behaved as XPS insulators. Insulating behavior was also observed on cooling the samples by passing liquid nitrogen through the spectrometer manipulator during analysis. The explanation of these phenomena is not yet clear but the apparent electrical conductivity allows XPS study of low vapor pressure organic liquids in a straightforward way, without charging effects.

ISSN:1055-5269    

DOI:10.1116/1.1247789

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

An x-ray photoelectron spectroscopy (XPS) analysis was performed of polypyrroles (PPy) electrosynthesized on Pt in aqueous solution. Spectra were recorded both for the as-synthesized (pristine) polymer (specimen 1) and for the so-called “overoxidized” PPy (specimen 2). Electrosynthesis was accomplished potentiostatically at +0.7 V vs SCE in KCl 10 mM containing pyrrole 0.4 M. Overoxidized PPy was obtained by keeping the pristine polymer at the electrosynthesis potential for 5 h, in phosphate buffer solution (pH 7). C, N, O (1s), and Cl 2p(pristine) spectra are included. Some minor elements, P (in the overoxidized polymer), Na (in some overoxidized samples), and Si (in other samples of both types of PPy, but not in those here reported), were also detected.

ISSN:1055-5269    

DOI:10.1116/1.1247790

出版商:American Vacuum Society    

年代:1994

数据来源: AIP