Telechelic urethane acrylate anionomer (UAA) chain showed less viscosity and polyelectrolyte behavior in water than dimethyl acetamide (DMAc) because of hydrophobic aggregation. UAA networks prepared in different solvents (water and DMAc) exhibited very different swelling behaviors in the same swelling medium, which can be interpreted as due to the very different microstructures formed in the solvents. UAA networks prepared with water (UAHG networks) had microphase-separated hydrophilic and hydrophobic domains, whereas UAA networks synthesized with DMAc (UADG networks) had relatively homogeneous network structures. The mechanical property of the UAHG and UADG networks, measured with a dynamic mechanical analyzer, was also very sensitive to the solvent type used during the crosslinking reaction. UAHG networks with a microphase-separated structure had a higher modulus than UADG networks. The results of the mechanical property measurements showed that water was a much better solvent for the hydrophilic hard segments of UAA chain than DMAc, even though DMAc dissolved both hydrophilic and hydrophobic segments of UAA chain.