Biomedical Engineering Reference
In-Depth Information
8
7
6
5
4
3
2
Layer 9 (PAH)
Layer 8 (PAA)
1
0
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
Fibre distance (mm)
Figure5.11
Forcetracesfromthewashingstepofafibretreatedwith8and9layersof low
molecularmassPAH/PAAadsorbedatpH5,withabackgroundelectrolyteconcentrationof
0.01MNaCl,andwashedunderthesameconditions.Thelowercurvesshowtheforcetrace
when thefibrewas immersed (advancing), and theupper curves showthe force tracewhen
thefibrewaswithdrawn(receding).ThefibrewastreatedwithPEMtoadepthof0.9mmand
washedtoadepthof1.7mm.Datafrom(41).
110
100
90
80
70
60
pH 7.5/3.5 HMw
pH 7.5/3.5 LMw
pH 5/5 LMw
pH 7.5/7.5 LMw
50
40
30
20
0
2
4
6
8
10
12
Number of layers
Figure 5.12
The advancing contact angle as a function of the number of layers on an
individual fibre treated with PAH/PAA (15000/8000) (LM
w
) at pH 5, 7.5/3.5, and 7.5/7.5
andwithPAH/PAA(70000/240000 (HM
w
) atpH7.5/3.5. Theadsorptionwascarriedout at
0.01MNaCl.Datafrom(35,41).
that there was a significantly larger difference in advancing contact angle depending on
the polyelectrolyte in the most external layer for the pH 7.5/3.5 adsorption strategy than
for the pH 7.5/7.5 strategy.
Since it is well known that the contact angle is influenced by the first nm of a polymer
film, the advancing contact angle can be used to estimate the difference in structure of
the PEMs formed. Small differences in contact angle may indicate very thin individual
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