2.3.5. Swelling Index

After 24 h of membrane creation, the samples were dried for 24 h in a container which contained granular calcium chloride. By this time, it had already been checked that the membrane weight was constant, so it was assured that the samples were completely dried.

In Figure 5, the dry aspect of the tri-layered activated crosslinked membranes can be observed.

Dehydrated tri-layered activated crosslinked membranes, from left to right: M3A-C76A-TX; M3A-C85H-TX; and M3A-C85A-TX.

The dried membranes were weighed and immersed in phosphate buffered solution (PBS, pH 7.4) at different times until reaching the maximum weight. Phosphate-buffered solution was prepared as previously reported. The membranes were immersed in phosphate buffered solution under constant agitation during the entire experiment.

The maximum swollen aspect of the different kinds of tri-layered activated crosslinked membranes can be observed in Figure 6.

Swollen tri-layered activated crosslinked membranes, from left to right: M3A-C76-TX; M3A-C85H-TX; and M3A-C85A-TX.

The weight of the swollen sample was measured with an electronic balance after the surface water was removed with filter paper. Then, the swelling index (SI) of the membranes was calculated by Equation (1):

where Wd and Ws are the weights of dried and swollen samples, respectively.