This gives the tiny cross linked sponges a great affinity for water. Polyacrylamide can absorb many times its mass in water. This property is useful in a variety of applica tions, such as in diapers and in potting soil. The polyacrylamide will release the absorbed water if a substance that interferes with hydrogen bonding is added. Ionic substances, such as salt, cause polyacrylamide to release its absorbed water.
Some polymers have the ability to interact with polarized light.
This interaction shows itself when the polymer is placed between polarizing filters whose axes are at a 90-degree angle to each other. In this arrange ment, very little light passes though both filters. When a substance that interacts with polarized light is placed between the filters, light will pass through the filters. Materials that interact with polarized light have either unsymmetrical molecules or an orderly but unsymmetrical arrangement of molecules. Certain polymers allow light to pass through crossed polarizing filters.