Towards homogeneous dynamics in incompatibile blends by selective transesterification

The evolution from two component dynamics towards homogeneous dynamics in originally incompatible blends of biodegradable aliphatic polyesters has been followed by dielectric spectroscopy. Transesterification reactions are responsible for the compatibilization process. However, our results indicate that the segmental dynamics are strongly modified even before any transesterification process is detected by 13C-NMR. This modification in the dynamics can be explained by incipient reactions at the interphase between the homopolymer rich regions, which further evolves to the interior of those phases by the formation of block copolymer of gradually decreasing block length. This process finally produces a random copolymer that forms a single phase with a single segmental relaxation.