Swelling behaviour of a non-ionic poly(N-vinyl-2-pyrrolidone) gel in a linear poly(acrylic acid) solution

The swelling behaviour of a non-ionic poly(N-vinyl-2-pyrrolidone) hydrogel in a linear poly(acrylic acid) solution upon the influence of chain length, pH, ionic strength, and water/dimethyl sulfoxide composition was studied. The sharp shrinkage of the gel volume within a narrow range of polyacid con centration takes place as a result of the formation of an intermacromolecul ar gel-polymer complex on the base of hydrogen bonding. According to X-ray diffraction this complex is amorphous. The formation of the gel-poly mer co mplex is a long term process and the system reaches equilibrium within 48 h . The swelling behaviour strongly depends on the chain length of the polyac id whereas it does not depend on the ionic strength. With increasing pH val ue and changing water/dimethyl sulfoxide composition the gel reswelling is induced. The complex formation with poly(acrylic acid) occurs in the same w ay for linear and crosslinked poly(N-vinyl-2-pyrrolidone).