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Molecular Design of Fluorocarbon Film Architecture by Pulsed Plasma Enhanced and Pyrolytic Chemical Vapor Deposition (1999)

Limb, Scott J. ; Lau, Kenneth K. S. ; Edell, David J. ; [et al.]

Springer

Plasmas and polymers 4 (1999), S. 21-32

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ISSN: 1572-8978

Keywords: Pulsed PECVD ; pyrolytic CVD ; HFPO ; fluorocarbon films ; PTFE

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology

Notes: Abstract Pulsed plasma enhanced chemical vapor deposition (pulsed PECVD) and pyrolytic chemical vapor deposition (pyrolyric CVD) of fluorocarbon films from hexafluoropropylene oxide (HFPO) have demonstrated the ability to molecularly design film architecture. Film structures ranging from highly amorphous crosslinked matrices to linear perfluoroalkyl chain crystallites can be established by reducing the modulation frequency of plasma discharge in plasma activated deposition and by eventually shifting mechanistically from an electrically activated to a thermally activated process. X-ray photoelectron spectroscopy (XPS) showed CF2 content increasing from 39–65 mol%. Fourier transform infrared spectroscopy (FTIR) showed an increasing resolution between the symmetric and asymmetric CF2 stretches, and a reduction in the intensity of the amorphous PTFE and CF3 bands. High-resolution solid-state 19F nuclear magnetic resonance spectroscopy (NMR) revealed an increasing CF2CF2CF2 character, with the pyrolytic CVD film much like bulk poly(tetrafluoroethylene) (PTFE). X-ray diffraction (XRD) patterns evidenced an increase in crystallinity, with the pyrolytic CVD film showing a characteristic peak at 2θ = 18° representing the (100) plane of the hexagonal structure of crystalline PTFE above 19°C.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021899414807

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Application of proton multiple-quantum NMR to the study of dynamics in bulk chloral polycarbonate (1994)

Roy, Ajoy K. ; Gleason, Karen K.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2235-2240

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ISSN: 0887-6266

Keywords: multiple quantum NMR ; polymer dynamics ; polycarbonate ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Proton multiple quantum (MQ) nuclear magnetic resonance (NMR) is applied for the first time to probe chain dynamics in the polycarbonate of 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene (chloral) over a temperature range of 195-280 K. Since chloral polycarbonate contains only one essentially indistinguishable proton, any dynamical information is associated with the phenylene group motion, the dominant sub-Tg motion. First, the fractional multiple quantum (fMQ) signal which can be refocused at a fixed MQ preparation time decreases with increase in temperature from 195 to 200 K, associated with the onset of the phenylene π flips. Since π flips do not modulate dipolar couplings between phenylene protons at positions 2 and 3 on the same ring, this decrease in fMQ can be attributed to modulation of the remaining couplings on the time scale of the MQ experiment. Next, over the range 200-240 K, the fMQ maintains a reduced, nonfluctuating value. This suggests a broad distribution of correlation times exists for the π flips, since at any one temperature in this intermediate range, only a small portion of the phenylene groups undergo motion at the precise kHz frequency required to refocus the MQ signal. The increase in the signal strength as the temperature rises above 240 K is due to the majority of π flips occurring in the fast motional limit. These observations are in agreement with previous single quantum proton NMR studies on phenylene group rotation in choral polycarbonate. Furthermore these fMQ measurements show several similarities to those for PTFE (poly(tetrafluoroethylene)), measured by 19F MQ-NMR. One notable difference is that in as-polymerized PTFE at intermediate temperatures (200-220 K) rapid oscillations of fMQ were noted as the temperature was changed by a few degrees. Such behavior is not observed in the chloral polycarbonate. © 1994 John Wiley & Sons, Inc.

Additional Material: 5 Ill.