Advances in the synthesis of bio-based aromatic polyesters: Novel copolymers derived from vanillic acid and \u3f5-caprolactone

A new and sustainable pathway for the synthesis of polyesters and copolyesters derived from vanillic acid is suggested. The poor reactivity of the fenolic -OH group of vanillic acid has been overcome by etherification reactions with biobased ethylene carbonate: the full procedure towards poly(ethylene vanillate) (PEV) avoids solvents and purification steps and uses only bio-based reagents. The PEV thus obtained is an example of bio-based PET mimics, characterized by high thermal transitions and a notable level of crystallinity. However, probably due to its low molecular weight, the material is brittle. In order to solve such problems and to exploit the aromatic structure of PEV to enhance the properties of aliphatic polyesters, new copolymers based on PEV and poly-\u3f5-caprolactone were prepared. The new materials are characterized by an EV crystalline phase and tunable thermal properties according to the composition

A Novel Approach for the Synthesis of Thermo-Responsive Co-Polyesters Incorporating Reversible Diels\u2013Alder Adducts

The proof of concept for a new copolymerization approach taking advantage of the thermally reversible aptitude of the furan/maleimide Diels\u2013Alder (DA) adducts is reported here. A new monomer bearing two carboxylic acids as end-groups and a Diels\u2013Alder adduct within its structure is synthesized using benign and mild reaction conditions. Two polyesters are then fabricated from the DA-diacid and 1,6-hexanediol and 1,4-benzenedimethanol, respectively, and characterized by 1H-NMR, GPC, DSC, and TGA. Kinetic studies of these polyesters, performed by 1H-NMR spectroscopy at variable temperatures, establish the appropriate conditions for their controlled depolymerization, through the retro Diels\u2013Alder reaction (rDA), and their re-construction through the DA reaction, showing moreover the reproducibility of this rDA/DA cycle. Finally, by exploiting this peculiar feature, a copolyester is successfully synthesized from the concomitant treatment of the two homopolymers, demonstrating the effectiveness of the method. The present approach provides a new method for the fabrication of multicomponent copolymers based on the DA/rDA strategy that is extendable to a variety of other polycondensation materials, such as polyesters, polyamides, polyurethanes, and epoxies, allowing the establishment of a library of novel architectures through this one-pot approach