The structure of amphiphilic hydrogels of copolymers of acrylic acid and n-alkylacrylate swollen by D2O was studied by small-angle neutron scattering (SANS). For most of the uncharged gels, a scattering peak is observed. It is attributed to the correlation between hydrophobic domains formed by self-assembled n-alkyl side chains. From the SANS data, the aggregation number of the hydrophobic domains was derived. It increases with increasing length of hydrophobic groups and also as a result of absorption of hydrophobic additives that are solubilized inside hydrophobic domains. The most important observation of this work consists of the fact that the introduction of charged groups into the gel leads to microphase separation with the formation of hydrophobic regions including several densely packed hydrophobic domains that alternate with hydrophilic regions swollen by water where most of the charged repeat units and counterions are located. The size of the hydrophobic regions decreases with increasing charge content. The microphase separation seems to be due to the effective interplay of two counteracting tendencies:  hydrophobic association and electrostatic repulsion. When salt screening is added, the microphase separation disappears.

The effect of the migration of charged units on the structure of hydrophobically modified polyelectrolyte gels swollen by D(2)O was studied by small-angle neutron scattering on an example of gels of terpolymers of acrylic acid, n-dodecylacrylate, and 2-acrylamido-2-methyl-1-propanesulfonic acid (quenched charged units) and gels of copolymers of partially neutralized acrylic acid and n-dodecylacrylate (annealed charged units). The content of charged units did not exceed 20 mol %, so that the electrostatic repulsion was too weak to disrupt the hydrophobic domains formed by self-assembled n-dodecyl chains, which was evidenced by NMR data. It was shown that upon increasing the charge content both types of gels undergo microphase separation with the formation of hydrophobic clusters consisting of several densely packed hydrophobic domains and hydrophilic regions swollen by water, where most of the charged repeat units and counterions are located. The dimensions of the nanostructure of the gels with quenched and annealed charged groups were compared. It was shown that the size of clusters in the gels with annealed charged units is much bigger than that in the gels with the same fraction of quenched charged units. This effect was attributed to a much weaker electrostatic repulsion in the corona of the hydrophobic clusters in the gels with annealed charged groups, because the charged units repelling each other are able to move farther apart.