Synthesis of Fluorine-Containing, UV-Responsive PLA-Based Materials by Means of Functionalized DOX Monomer

1,3-Dioxolan-4-ones (DOX) chemistry is exploited for the synthesis of UV-curable, polylactic acid (PLA)-based copolymers. DOX monomer functionalized with 4-fluoro-4 '-hydroxybenzophenone is synthesized and employed as comonomer with l-lactide. Copolymerization reactions are performed with different DOX loadings through a solvent-free, metal-catalyzed protocol. Products are characterized through NMR analysis in order to demonstrate the random insertion of the modified monomer within the polymeric chain. Copolymers are subjected to UV irradiation and compared to a control PLA synthesized and processed in the same conditions. The evolution of the molecular weight during prolonged UV exposure is evaluated through SEC analysis, showing the effect of the benzophenone side groups, which promote crosslinking reactions. A crosslinking mechanism is proposed and demonstrated by means of H-1 NMR and FT-IR analyses. The gel content of the samples is measured after the UV exposure, demonstrating a correlation with the concentration of DOX-derived units. Finally, water contact angle analyses are performed to investigate the effects of the fluorination degree on the wettability properties and thermal characterization is carried out. Moreover, rheological analyses show a shear thickening behavior for the copolymers with the highest concentration of DOX-derived units.