Chain flexibility effect, degradation

In solution, an additional factor is involved the interaction between polymer and solvent. This feature is detailed in Volume 2, Chapter VIIB. The related effect of polymer chain flexibility in solution has also been demonstrated in ultrasonic degradation by a lower degradation of natural (c/5-isoprene) rubber when compared with the trans conformer [30],... 

Aliphatic polyesters are perhaps some of the most easily biodegraded polymers found in nature. One reason for this is the effect that chain flexibility has on biodegradability. For degradation of polymers by enzymes, the polymer chain must be flexible enough to fit into the active site of the enzyme. This characteristic most likely accounts for the biodegradability of aliphatic polyesters, which are flexible, whereas wholly aromatic polyesters, which are more rigid, are generally considered bioinert. 

For recently prepared terpolymers of PO/CO2 noticeable improvements in thermal stability were thus achieved. The rate of decomposition decreases with the termonomer content. Part of the effect obviously originates from the lower concentration of propylene carbonate entities and another part from the lower flexibility of the main chain. In addition, another explanation for the increase in thermal stability with termonomers (which is, however, not substantiated) could be found in the solubility of water in the product because every recent study indicates that hydrolysis is a major cause of the initiation of thermal decomposition [23]. Also, additives have been identified as slowing down thermal degradation. 

Basically all factors are important which display an effect on the solubility of the macromolecule and its flexibility, i.e., the capacity for deformation of the polymer backbone. According to Brostow s theory, there are two effects of central importance for practical application degradation and relaxation. Every type of energy transferred to a polymer chain in solution does so via one of these two processes. Thus, all parameters which directly affect these processes are of corresponding significance. 

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