Polytetrahydrofuran amphiphilic networks. IV. Swelling behavior of poly(acrylic acid)-l-polytetrahydrofuran and poly(methacrylic acid)-l-polytetrahydrofuran networks

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 diacrylate s with hydrophilic acrylic acid and methacrylic acid. Their swelling behavi or was studied. Both PAA-l-PTHF and PMAA-l-PTHF networks had four solubilit y parameters, which indicated that they exhibited not only the properties o f both hydrophobic and hydrophilic segments but also the combined propertie s of these two segments. The swell of these two series of networks was comp osition-dependent in organic solvents and water. The relationship between t he equilibrium swelling ratio (SR,) in nonpolar solvents and the compositio n 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 paramete rs that relate to the interaction of hydrophilic and hydrophobic segments w ith 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 sensi tivity of networks could be controlled not only by the composition of the n etworks but also by the hydrophobic degree of the hydrophilic segments. (C) 2001 John Wiley & Sons, Inc.