114
6 Fabrication of Robust Biomolecular Patterns …
Fig. 6.2 XPS element scans of neat PNHSMA film on oxidized silicon and PNHSMA film after
grafting with PEG 500 -NH 2 by reactive μCP
Table 6.1 XPS data of
PNHSMA films before and
after grafting of PEG 500 -NH 2
Sample
Theoretical C/N
ratio
Experimental C/N
ratio
(μCP)
PNHSMA film
8
8.0 ± 0.4
PNHSMA fully
PEG-covered
22
9.8 ± 1.0
~11% of all NHS ester groups have been reacted with PEG 500 -NH 2 . A formal grafting
density of PEG of ~2.8 PEG molecules per nm
2 was thus estimated. This value is
in excellent agreement with the ellipsometry data discussed above and confirms that
PNHSMA films are loaded very efficiently with PEG by reactive μCP. Similar to
the coupling reaction in solution, the coupling reactions during reactive μCP are
very likely not limited to the very surface of the polymer films, but proceed into the
surface-near regions of the films.
6 Fabrication of Robust Biomolecular Patterns …
Fig. 6.2 XPS element scans of neat PNHSMA film on oxidized silicon and PNHSMA film after
grafting with PEG 500 -NH 2 by reactive μCP
Table 6.1 XPS data of
PNHSMA films before and
after grafting of PEG 500 -NH 2
Sample
Theoretical C/N
ratio
Experimental C/N
ratio
(μCP)
PNHSMA film
8
8.0 ± 0.4
PNHSMA fully
PEG-covered
22
9.8 ± 1.0
~11% of all NHS ester groups have been reacted with PEG 500 -NH 2 . A formal grafting
density of PEG of ~2.8 PEG molecules per nm
2 was thus estimated. This value is
in excellent agreement with the ellipsometry data discussed above and confirms that
PNHSMA films are loaded very efficiently with PEG by reactive μCP. Similar to
the coupling reaction in solution, the coupling reactions during reactive μCP are
very likely not limited to the very surface of the polymer films, but proceed into the
surface-near regions of the films.