Biomedical Engineering Reference
In-Depth Information
Box 4:
Information gained from FTIR and XPS for examples of grafted
substrates
Carboxylate Carboxylate groups on a polyester can be detected by FTIR
(example of an AA grafted PLGA film is shown in Figure
11.1A and 1B). In the 4000-2000 cm
1
region, the very broad
band from the OH vibrational mode appears clearly after
grafting while in the 2000 to 600 cm
1
region the most
distinct change is from a single carbonyl stretch from the
ester group at 1750 cm
1
in the unmodified polymer
substrate to an additional carbonyl stretch at lower
wavenumber (1700 cm
1
) for the carboxylic acid group in
the grafted substrate.
11,14,32
Relative amounts of acid and ester moieties can be obtained by
FTIR or Raman spectroscopy.
14
d
n
3
r
4
n
g
|
2
Amine
Amine groups can be detected by FTIR by the presence of a
amine vibrational modes at 1610 and 750 cm
1
.
18,33
Amine groups on a polyester substrate are detected and
quantified by XPS as a new element is introduced during the
grafting process.
18,33,50
XPS can be used to evaluate the relative amounts of
various nitrogen-containing functional groups such as
amine, amide and protonated amines
18
and thus is a
useful tool to assess the level of e.g., surface oxidation of
amine groups.
87,88
Sulfate
Sufate groups on a polyester substrate can be detected by
XPS as a new element is introduced during the grafting
process.
52
Sulfate groups display a strong band due to the S
ΒΌ
O symmetric
stretching in the 1230-1250 cm
1
region.
89
.
chemical information regarding the surface layer and structural information
based on the molecular fragments observed. Like XPS, this technique re-
quires the sample to be in a vacuum and no volatiles can be present. The
data sets obtained from ToF-SIMS are very complex and are routinely cou-
pled with detailed principal component analysis to evaluate chemical dif-
ferences between samples.
72
Energy dispersive X-ray (EDX) spectroscopy
coupled to scanning electron microscopy (SEM) analysis has also been ap-
plied in a few studies. However, it is restricted to information regarding
elemental composition and it is dicult to obtain quantitative data for
samples that are not smooth.
It should, of course, be noted that while these different techniques used
for the characterisation of the surface chemistry are indeed complementary,
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