I can't tell if all the sodium polyacrylate dissociates. It depends on the amount of water.
A hydrogen bond happens between neutral species, for instance between two water molecules. Here the carboxylate and the sodium ions are charged, this makes a stronger bond with the polar water molecules. It resembles closely the dissolution of NaCl in water, where Na+ attracts the negatively polarized side of H2O and Cl- the positively polarized side. If water is in small amount, it resembles the dessication by CaCl2. The difference by sodium polyacrylate is that the negative ion remains a long polymer chain.
Both ions attract water. But since all + ions can't separate from all - ions due to the huge attraction, only the sum of both effects is observed.