The rheol. properties of carboxyvinyl polymer (CVP) hydrogels were evaluated using various methodologies.As CVPs, the series of Hiviswako (HVW) 103, 104, and 105 (denoted as H103, H104, H105, resp.), and Carbopol (CP) 934, 940, and 941 (denoted as C934, C940, C941, resp.) were used.In the HVW series, the order of magnitude of intrinsic viscosities obtained by the capillary tube method was H105 > H104 > H103 at all pH values examinedThis order agreed with that of the viscoelastic parameters obtained by the oscillation method and that of the viscosity obtained by the continuous shear method when the gels were in a non-neutralized state.However, the orders were reversed when they were partially neutralized by adding alkali.From these results, the gel structure of each polymer was presumed to be as follows.In the case of H103, the polymer is rich in side chains or crosslinks and takes a compact form in the nonneutralized state.When alkali is added to H103, side chains are extruded into the water phase by the elec. repulsive forces between carboxyl groups, and the polymer mols. become entangled with each other, so that the gel shows larger viscoelastic values.On the other hand, in the case of H105, the polymer is poor in side chains and the addition of alkali has less effect on the viscoelastic properties than in the case of H103 or H104, due to the lack of entanglement of side chains.The viscoelastic properties measured in glycol solutions and the swelling rate for the HVWs supported the above hypothesis.As regards CVP, C941 showed almost the same properties as H105.C934 and C940 showed similar properties to H103 and H104 resp., although some differences were observed among them.
