Dynamic mechanical characterization of molecular motion in a wide temperature range of various polymers containing propylene units

The temperature transitions for a series of flexible polymers containing pr opylene units were studied by dynamic mechanical spectroscopy. It was found that the gradual activation of the local motion of different structural un its involved in polymers occurs with increasing temperature. Initially, the rotation of the side groups, such as side methyl groups, is activated and on further heating the main chain structural units show their local motions . It is important that the temperature interval of the appearance of the lo cal motion of each structural unit is almost independent of the presence of other structural units. Accordingly, the polymers investigated can be divi ded into two groups. The activation of the local motion of the most rigid s tructural unit determines the glass transition in the first group of polyme rs. The glass transition of the polymers of the second group takes place at a higher temperature which depends on the content of side methyl groups an d the intermolecular interaction. The increased influence of both these fac tors on the cooperative amorphous motion of polymers of the second group le ads to their increased T-g values.