Grafting of Functional Monomers on Biomaterials - Biointerfaces: Where Material Meets Biology - page 336

of the conclusions are completely wrong, nor are they completely right in the
sense that none of the techniques provides the full picture. It is thus desir-
able to use multiple techniques for the analysis in order to get a full picture of
the position of the grafted chains. 8 Alternatively, the penetration of the
grafted chains can be probed directly by cross-section analysis.
Cross-sections of grafted polymer substrates may be analysed using a
variety of techniques as evident from the data in Table 11.4 for porous
substrates. Such an approach is also used for solid substrates, and for this
purpose the use of Raman spectroscopy is common. 14,105 An example of
Raman mapping across the cross-sections for a series of PCL films is shown
in Figure 11.4. The carbonyl band of the ester from the PCL substrate and
the carbonyl band from the introduced grafted PAA chains were used in the
analysis and it is clearly evident that the penetration depth of the graft co-
polymer is highly dependent on the solvent used during the grafting pro-
cess. 14 The disadvantage of using any technique that requires destructive
sample preparation, such as resin embedding or cross-sectioning, is that it
can cause the introduction of artefacts. Cross-sectioning of highly porous
substrates, particularly when soft in nature, can also be a challenge because
this can cause deformation of the sample.

d n 3 r 4 n g | 2

.

Figure 11.4 Effect of grafting conditions of AA on PCL using simultaneous
grafting in different solvents. (A) Untreated PCL; (B) sample grafted
in water; (C) sample grafted in a mixed solvent (water-methanol)
solvent system. Data represent graft penetration depth as evaluated
from the area ratios of the CQO stretch of the acid and the CQO stretch
of the ester from Raman spectroscopy.
Data obtained from ref. 14.