Polysaccharides are long chains of simple sugars that contain several hydroxyl groups on each sugar. These hydroxyl groups interact very strongly with water because of the polarity of the oxygen-hydrogen bond. A single molecule of cellulose can contain hundreds of hydroxl groups. The affinity that nylons have for water also comes from polar bonds. This bond is typically formed between a carboxylic acid and an amine, and contains carbon, oxygen, nitrogen, and hydrogen atoms.
Nylons are also long chains of smaller molecules, each linked by one of the amide bonds.
Each of these linkages provides a site where water can bind. Cotton can absorb up to 27 times its weight in water, whereas Nylon 66 will absorb only around 10 percent of its weight water. This month's Whizard is Dr. Mark Van Dyke, a senior research scientist in the Materials Development section of the Mechanical and Materials Engineering Division.