The relative amount of water absorbed by the coatings was studied by FTIR spectroscopy in the ATR mode.
For all systems, a growth of two bands within the 3800–3000 cm−1 region and
around 1640 cm−1 was observed upon immersion in 3.5% NaCl solution.
These bands are respectively related to the stretching, (OH)
and in plane bending, ı(OH) of water molecules.
Up to a 15% difference in maximum absorbance was observed for two different pieces of the same wet material.
Consequently, no quantitative analysis of the water diffusion was performed. Nevertheless, the results in Fig. 7 demonstrate a clear effect of PANI content and nature of dopant on sorption. It can be seen that PANI–LS1 and
PANI–BS have a negative effect on the sorption properties.
The amount of water absorbed increases with the amount of these additives.
On the contrary, PANI–LS2 additives seems to have a positive
effect on the sorption properties as indicated by the lower
amount of absorbed water than all other systems.
It is tempting to draw a parallel between the conductivity of PANI–LSs and
their effect on sorption process, namely a low conductivity of the
PANI–LS is beneficial to the water absorption properties of the coating.