Reversible networks of degradable polyesters containing weak covalent bonds

Abstract

In the past few years, we have observed the continuous emergence of new polymeric materials capable of reversibly adapting to their environment. Polymer networks containing reversibly formed covalent bonds may be considered as such materials. Among the various types of networks based on chemically different polymers, there are also polyesters. The increasing interest in polyesters is due to their biodegradability and biocompatibility and the fact that their production may be based on renewable resources. Stimuli-responsive reversibly crosslinked polyesters are designed as shape-memory or self-healing materials e.g. for biomedical applications; however, their capability for thermoplastic behavior after appropriate actuation is also important in processing because of the polyesters’ established position as technological commodity plastics. This review covers cases of reversible polyester network preparation presented in the literature, classifying them according to the used method or the type of chemical reactions enabling reversible network rearrangement. Only a selected few chemistries have been used to create reversible polyester networks to date. Thus, in this paper, the prepared polyester networks which were reversible by the application of the Diels–Alder chemistry, dimerization of the cinnamoyl/coumarin group or by catalyzed transesterification reactions are described, in particular with respect to the methods for their synthesis and studies of their reversibility. The effects of the network reversibility such as shape-memory and/or self-healing properties or the capability for reprocessing/recycling are presented. The features specific to polyesters, e.g. the capability for crystallization influencing the formation and behavior of discussed networks, are particularly highlighted. Finally, the strengths and weaknesses of the attempted approaches are discussed and suggestions for new methods are made.