2.1.8.2. Absorbency Under Load (AUL) - BADA

The extent of reaction can be evaluated by measuring of lysyl residues in free amino groups before
and after reaction. This modified albumin will use in polymerization onto acryl amide, vinyl
pyrolidone, acrylic acid and glycidyl acrylate as a crosslinker. If vinyl or epoxy groups will be less
than 10% of total amino groups of protein, such kind modified proteins will not be efficient
crosslinker and hydrogel can not be formed as well [45] .
1.9.2.2. Albumin as a Backbone
Albumin can modify by acylation reaction in order to obtain maximum hydrophilization of protein.
The acylated and lyophilized albumin will be immobilized by bifunctional crosslinker such as
glutaraldehyde. The rest of ε-amino groups after acylation by EDTAD react with glutaraldehyde to
form crosslinked hydrogel.
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1.10. Effect of Superabsorbent structure on Swelling
Swelling is a diffusion phenomenon motivated by the affinity of the absorbent molecules for the
molecules of the contacting liquid. Figure 14 shows five models of swollen superabsorbent gel
structures. The first Figure (a), a typical crosslinked network, has swelling limit controlled by
equilibrium between thermodynamic forces due to polymer solvent interactions and entropic force
of coiled polymer chains. The second model (b) is similar as a Pseudo-crosslink, which generally
is an insoluble crystalline phase. In some terms model (b) may reversively transform to model (C)
as a polymer diluted matrix. The (d) model is a similar to house of cards structure and also
Paracrystaline state (e), which both of them are colloidal in characterization. In fact current
absorbent materials are more commonly represented as model (a) or (b) [46] .
Figure 14. Five models of swollen superabsorbent hydrogel structures
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