Effect of Middle Diol Repeat Units in Biobased Aliphatic Polyesters on Thermal and Tensile Properties

Biobased aliphatic polyesters derived from multiple nonedible plant resources generally display rather facile chemical recyclability, and their physical and chemical properties are affected by the monomer design. The polyesters consisting of 10-undecenoic acid (derived from castor oil) not only with monomeric diols [(1R,2R)-1,2-cyclohexanedimethanol, (+)-2,3-O-isopropylidene-L-threitol (LTh), and 1,9-diethyl L-(+)-tartrate] but also with long-chain diols consisting of isomannide (IM) or LTh connected through trans-1,4-cyclohexane dicarboxylic acid or 2,5-furane dicarboxylic acid (M4-M7) were prepared by acyclic diene metathesis (ADMET) polymerization and subsequent tandem hydrogenation. The thermal properties of the resultant polymers were affected by the diol middle segment employed, whereas the polymers consisting of a diol unit of two LTh or IM connected with the dicarboxylic acid were amorphous. Tensile properties in the prepared polymer films were also affected by the middle diol repeat units. Polyesters consisting of 10-undecenoic acid and two IM connected through trans-1,4-cyclohexane dicarboxylic acid [expressed as P7 (prepared by ADMET polymerization), and HP7 (saturated polyester after hydrogenation)] showed promising tensile stress and strain (elongation) at break, with observation of the yield strength. The observed values [stress 26.9 MPa, strain 449% (P7); 35.7 MPa, 349% (HP7)], especially the tensile strength (stress) at break, were larger than those of the reported polyester films consisting of IM or isosorbide. In contrast, similar polyester films containing 2,5-furan dicarboxylic acid showed brittle fracture behavior without yielding.