Biomedical Engineering Reference
In-Depth Information
(a)
(b)
Figure 7.10 AFMTappingmode height images of a 55 nm thick lignin surface. (a) 5.0
×
5.0 µ m 2 ,RMSroughness1.01nm. (b)1.0
1.0 µ m 2 RMSroughness0.59nm.Peak-to-peak
roughness is less than10nmonthe25 µ m 2 image. Thesurfaceroughnessdoesnot change
significantlywiththethicknessoftheligninfilm.AdaptedwithpermissionfromNorgrenetal.
(2006).Copyright(2006),AmericanChemicalSociety.
×
pH 10
1600
4
500
pH 10
H 2 O
2
pH 3.5
pH 7 pH 8.5 pH 9
pH 9.5
pH 10
1400
400
1200
2
1
pH 11
1000
300
0
800
0
200
600
100
1
400
2
pH 10
200
0
2
0
4
0
5
10
15
20
25
30
35
40
0
20
40
60
80
100
Time (minutes)
Time (minutes)
Figure7.11 Theeffectofalkalinityonthestabilityofaspin-coatedligninfilmasmonitored
byQCM-D.Thearrows indicatethegivencharacteristicsof therinsingfluidintroducedinto
the measuring chamber. Adapted with permission fromNorgren etal. (2007). Copyright
(2007),AmericanChemicalSociety.
A subsequent study using lignin films spin-cast on silica coated quartz crystals surfaces
used in the quartz crystal microbalance showed no effect on the uptake of solvent or
degradation of the film at pH less than 9.5 as shown in Figure 7.11. However, with
further increases to the solution pH, the films initially became swollen at pH 10 before
completely dissolving from the underlying substrate at pH 11. This study demonstrates
the limitation of these particular softwood kraft lignin films for use in other fundamental
investigations involving the interactions of solid state lignin. The stability of the kraft
lignin films closely resembles the solubility of the kraft lignin in solution, that is, at pH
greater than 10, the films delaminate from the silica supporting substrate and dissolve
into solution.
Search WWH ::




Custom Search