Applications of ESCA to polymer chemistry. III. Structures and bonding in homopolymers of ethylene and the fluoroethylenes and determination of the compositions of fluoro copolymers

Abstract

Molecular core binding energies have been measured by ESCA for the homopolymers of ethylene and the fluoroethylenes. The data are interpreted in terms of semiempirical all‐valence electron SCF MO calculations in the CNDO/2 formalism, in conjunction with the charge potential model. The results are used as a basis for interpreting the measured core binding energies of some Viton and Kel F type polymers. The routine application of ESCA to the determination of copolymer compositions is described.

Aluminum doping of poly(vinylidene fluoride with trifluoroethylene) copolymer

“…16 These reported binding energies ͑for polymers with no evidence of crystallinity and an indeterminate local bonding geometry͒ are all far larger than those observed here for crystalline PVDF-TrFE. The differences in core level binding energies can be understood to be a consequence of final state screening effects.…”

“…The relative intensity of the higher binding energy C 1s core level (CF 2 ) decreases significantly ͓Fig 1͑a͔͒. Since it has already been established that -CH 2 -sits high on the surface ͑toward the vacuum͒, 16 we can attribute the core level shift of the C 1s binding energy for CH 2 ͑the lower binding energy C 1s core level͒ to surface screening. The higher binding energy C 1s core level may be due to the CF 2 , as previously assigned, 15 though more likely ͑on the basis of the data presented here͒ this higher lying C 1s core is due to an unscreened final state ͑in the just described scheme͒ and not sensitive to the higher surface density of states ͑and concomitant screening͒ because the surface carbon in CF 2 , as well as the carbon atoms in the ''bulk'' polymer sits below the plane of the surface.…”

Purification of Peptides in High-Complexity Arrays

“…All spectra measured on silicon wafers or glass substrates were normalized to the alkylic C1s signal at 284.6 eV. Spectra of PVDF membranes were normalized to the CH2 signal at 286.3 eV, [164] whereas spectra measured on gold-coated membranes were normalized to the Au4f 7/2 signal at 84.21 eV. [179] Integration for the quantitative analysis of the signals was also performed with the Origin peak fitting module.…”

“…[164] The hydrophilic modification of the Durapore membrane became visible in an additional O1s signal, a less intense F1s signal, and a different signal structure in the C1s area (red lines). Upon TFA treatment of the hydrophilic membrane the C1s signal structure changed, the F1s signal intensity further decreased, and the O1s signal became more pronounced.…”

“…Untreated PVDF typically shows only two C1s peaks at 290.8 eV (C-F) and 286.3 eV (C-H). [164] Although no detailed information was provided by the manufacturer, it was communicated that the surface coating was covalently bound. [165] In the peptide array purification, a hydrophilic surface was favored to avoid nonspecific adsorption of peptide fragments in the purification step or proteins in subsequent immunostainings.…”