A closer look
Cross-linked polymers are chemically desperate for water. Superabsorbent hydrogels are composed of sprawling molecular chains lined with sodium molecules. When exposed to liquid, osmosis forcefully drives water molecules directly into the polymer network to balance the massive sodium concentration. The rigid chemical cross-links prevent the structure from dissolving, forcing the plastic granules to aggressively swell into massive, squishy gel blobs holding hundreds of times their initial mass in liquid.
