Novel green route towards polyesters-based resin by photopolymerization of star polymers

Bio-based star-shaped poly(epsilon-caprolactone)s (S-PCL) derived from sugar-based D-sorbitol as an initiator were obtained via solvent-free enzymatic ring-opening polymerization (CROP). The star S-PCL were converted into UV-curable maleates by employing maleic anhydride for subsequent crosslinking with tri(ethylene glycol) divinyl ether (DVE-3) in the presence of Darocur 1173 as a radical photoinitiator. The kinetics of the UV-induced radical copolymerization was monitored by real-time Fourier-Transform InfraRed (FTIR) spectroscopy, which revealed that the star S-PCL maleate/divinyl ether system was not scavenged by molecular oxygen (donor/acceptor polymerization). The UV-crosslinking reaction was fast (similar to 10 s) to reach near quantitative conversions. The S-PCL maleate / divinyl ether liquid formulation cast on glass substrates successfully gave films upon UV-crosslinking. The thermal properties of the polymer films and their precursor polymers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Finally, the crosslinked polymer film demonstrated promising adhesive properties on steel, aluminum and glass substrates.