Poly(acrylic acid)-l-polytetrahydrofuran (PAA-l-PTHF) and poly(methacrylic acid)-l-polytetrahydrofuran (PMAA-l-PTHF) networks were synthesized by the free-radical copolymerization of hydrophobic polytetrahydrofuran diacrylates with hydrophilic acrylic acid and methacrylic acid. Their swelling behavior was studied. Both PAA-l-PTHF and PMAA-l-PTHF networks had four solubility parameters, which indicated that they exhibited not only the properties of both hydrophobic and hydrophilic segments but also the combined properties of these two segments. The swell of these two series of networks was composition-dependent in organic solvents and water. The relationship between the equilibrium swelling ratio (SR,) in nonpolar solvents and the composition of the networks [the weight fraction of the PTHF segment (PTHF%)] may be expressed with a linear equation: SRe = A x PTHF% + B. A and B are parameters that relate to the interaction of hydrophilic and hydrophobic segments with nonpolar solvents and to the properties of the networks, respectively. Because of the presence of a -COOH group, these two network series were pH-sensitive when the content of hydrophilic segments was higher. The pH sensitivity of networks could be controlled not only by the composition of the networks but also by the hydrophobic degree of the hydrophilic segments.