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Figure 2 shows the successful coating of plasma polymerized hexafluoro-m-xylene
on ZrO2. Polymerization through plasma agitation always leads to an amorphous
coating that can be clearly distinguished from the dark and crystalline oxide core. In
all cases, oxide particles can be produced with diameters smaller than 10 nm and
varying coating thickness of 2 - 10 nm.
Fig. 2: Transmission electron micrograph of
an amorphous polymer coating on the zirconia
core (Image by R. Schierholz, Structural
research division).
Transmittance T [a.u.]
3180
ν (N-H)
ν (C-H)
ppECA/
SiO (p)
2
CO
2
ppMMA/
SiO 2
SiO 2
1600
ν
1710
(C=C)
ν (-C=O)
δ (C-H)
880
δ (Si(CH 3 ) 2 )
3000 2000 1000
Wavenumber [cm -1 ]
*
*
*
* SiO 2
*
*
*
664
δ (N-H 2 )
Fig. 3: FT-IR spectra of uncoated silica, silica
coated with plasma polymerized MMA
(ppMMA/SiO2) and silica coated with plasma
polymerized ECA (ppECA/SiO2).
The influence of the coating material on the dispersability was studied in the case of
the acrylate-based coatings ppMMA and ppECA on silica [3] . Powders derived from
methylmethacrylate are characterised by a hydrophobic surface, making it impossible
to disperse them in water. The powders are not wettable. The exchange of a methyl
group to a cyano group (-CN) in the monomer leads to enhanced dispersability in
water. In the plasma, the C≡N bond is split and reassembled with hydrogen in the
coating to form –NH2 groups, as determined by FT-IR spectroscopy (Fig. 3). The
hydrocarbon bands of the coating can be found in the range of 2875 – 2960 cm -1 .
Vibrations of the methacrylate can be identified around 1710 cm -1 for the C=O bond
and around 1600 cm -1 for the double bonded carbon. The vibrations responsible for
δ(N-H2) around 664 cm -1 and for ν(N-H) around 3180 cm -1 appear only in the
spectrum measured on particles coated with ECA-derived coatings.
Literatur:
[1] J. Suffner, Diploma thesis, Faculty of Materials- and Geo-Sciences (TU
Darmstadt), 2006
[2] M. Schallehn, M. Winterer, T.E. Weidrich, U. Keiderling, H. Hahn, Chem. Vap.
Deposition 2001, 9, 40.
[3] J. Suffner, G. Schechner, H. Sieger, H. Hahn, Chem. Vap. Deposition
(accepted for publication)
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