Synthesis of unsaturated polyesters based on renewable monomers: Structure/properties relationship and crosslinking with 2-hydroxyethyl methacrylate

This work presents the preparation of unsaturated polyesters (UPs) with 'high green content' and their crosslinking reaction with 2-hydroxyethyl methacrylate (HEMA), to yield the unsaturated polyester resins (UPRs). The chemical structure analysis revealed the presence of mesaconate moieties in the UPs prepared with itaconic acid (IA) as the unsaturated diacid. These UPs were also characterized by high values of polydispersity (PDI), which is indicative of the presence of branched structures. The UPs have shown good thermal stability. The UPRs presented high gel content, which has shown to be dependent on the amount of HEMA in the formulation. The dynamic mechanical thermal analysis (DMTA) revealed the existence of two transitions, corresponding to the motion of different domains in the UPRs. The swelling tests revealed that the UPRs have a highly hydrophobic nature. The in vitro hydrolytic degradation tests showed that the UPRs are hardly degraded in a phosphate buffered saline solution (PBS), at pH = 7.4 and 37 °C.