MECHANICAL LOSS PROCESSES IN POLYSACCHARIDES

In the reported study, dynamic mechanical properties of cellophane, amylose, and dextran have been obtained over the temperature range 100-520 degree K and frequency range 10** minus **2 to 10** plus **2 Hz on specimens containing various amounts of water. Four mechanical transitions have been characterized. At about 180 degree K, there is a gamma transition that has been assigned to rotation of methylol groups; no comparable transition was found to exist in dextran. At about 240 degree K, there is a beta transition that has been assigned to rotation of methylol - water complexes, but the beta transition in dextran appears to be due to some other kind of motion. In cellophane at about 450 degree K there is an alpha //2 transition which appears to have contributions from motion of chain segments in disordered regions. The changes in these mechanical loss mechanisms due to moisture uptake suggest that sorbed water associates with glucose repeat units in ways ranging from those which stiffen molecular structure to those which allow greater freedom for other types of motion to occur.