Recebido em 25/2/12; aceito em 27/7/12; publicado na web em 27/11/12 SYNTHESIS AND CHARACTERIZATION OF POLY (ACRYLAMIDE-CO-ACRYLATE) AND KAOLIN HYDROGEL COMPOSITES: EFFECT OF THE CONSTITUTION OF DIFFERENT KAOLINS FROM NORTHEASTERN BRAZIL. Superabsorbent hydrogels based on poly (acrylamide-co-acrylate) and different kaolins, were prepared by free-radical aqueous copolymerization. FTIR and WAXS techniques were employed for characterization of a series of hydrogels, obtained by varying the percentage of clay, crosslinking and constitution of kaolin. The water absorbency at equilibrium (W eq ) decreased with increasing clay content and the amount of crosslinking agent. Superabsorbent hydrogel (W eq > 1084 g H 2 O/g gel) was obtained as 10 wt% of white kaolin and 0.05 mol% of crosslinking agent were used. The hydrogel proved sensitive to pH variation and the presence of salts.