Synthesis and characterization of fully biobased polyesters with tunable branched architectures†
A series of sugar-derived triols and biobased diacids were combined to prepare fully biobased branched polyesters with different structural features by melt polycondensation. By applying the BiMolecular Non-Linear Polymerization methodology (BMNLP), the molar ratio of diacid/triols was varied to access branched polyesters bearing either hydroxyl or carboxyl moieties as end groups. The structural features of the resulting polymers were scrutinized by 1H/13C NMR, and FT-IR spectroscopies, whereas DSC and TGA were used to investigate their thermal properties. The structure–property relationship of the synthesized polyesters was correlated to the structure of the triols and diacids and their molar ratio. Both prepared carboxyl-ended and hydroxyl-ended branched polyesters were amorphous with relatively low glass transition temperatures ranging between −57 and −18 °C for hydroxyl terminated polyesters while for carboxyl terminated ones, they oscillate between −37 and 19 °C. All these polyesters exhibit good heat resistance with onset degradation temperature Td,5% ranging from 180 to 268 °C and from 168 to 236 °C for COOH- and OH-end groups-bearing polymers series, respectively. The structural features and properties of the resulting branched fully biobased polyesters make them not only potential candidates for a wide range of applications but also as intermediate substrates for further chemical modifications and/or chain extension to access a wide range of functional (co)polymer materials.