Two types of reversible hydrogels formed by poly(t-butyl acrylate)-poly(2-vinyl pyridine)-poly(t-butyl acrylate) (PtBA-P2VP-PtBA) and poly(acrylic acid)-poly(2-vinyl pyridine)-poly(acrylic acid) (PAA-P2VP-PAA), named telechelic polyelectrolyte and block polyampholyte, respectively, of the same degree of polymerization were studied in aqueous solutions at pH 3.7 in terms of their theological properties. The different structural characteristics of the formed 3D networks that arise from hydrophobic interactions of the telechelic polyelectrolyte and electrostatic interactions of the polyampholyte, lead to significant different theological properties. The results tend to show that a thermo-sensitive weak hydrogel is formed by the polyampholyte while a stiff, but fragile, hydrogel is formed by the telechelic polyelectrolyte. (c) 2008 Elsevier Ltd. All rights reserved.