Facile Sustainable Synthesis of Polyester-Polycarbonate and Effects of the Carbonate on Thermal, Mechanical, and Transparency Properties

Abstract

The development of sustainable packaging materials can mitigate the carbon emissions caused by petroleum-based feedstocks, but economically viable polymers that combine stable mechanical properties with transparency remain an issue. This study reports a facile, sustainable one-pot synthesis of polyesterpolycarbonates (PCCTs) through diol end-group shielding by using monomers derived from carbon dioxide (CO 2 ). Copolymerization of dimethyl carbonate (DMC) and dimethyl terephthalate with 1,4-cyclohexanedimethanol (CHDM) in varying molar ratios was carried out, and the resulting PCCTs exhibited exceptional optical, thermal, and mechanical properties. The incorporation of DMC and CHDM units was found to significantly impact the thermal and optical characteristics of the PCCTs. The copolyester containing 40 to 90 mol % DMC content demonstrated full amorphousness and high transparency, with a Haze value downgrade to less than 5% and visible light transmittance upgrade to 92%. PCCTs maintained a suitable glass transition temperature range of 42.00−81.21 °C. Notably, the mechanical properties of PCCTs are similar to those of commercial glycol-modified polyethylene terephthalate, with an increase in tensile strength from 41.3 to 52.4 MPa and elongation at break from 8.1 to 244.0%. Given the environmentally friendly synthetic process and exceptional performance of PCCTs, these copolyesters possess significant potential for mainly application in packaging fields.

Synthesis of Thermal-Resistant Polyester-Polycarbonate with Fully Rigid Structure from Biobased Isosorbide

“…Due to the particular exo-/endosecondary hydroxyl groups and spatial structure of IS, it is difficult to prepare high molar ratio isosorbide-based copolyesters by conventional preparation methods. In our previous work, rigid polyester-polycarbonate was prepared by shielding the terminal hydroxyl groups with excellent results . Therefore, the green and efficient polymerization method based on the excess of −OCH 3 groups was used to alleviate the negative impact of IS and a series of PCCITs were prepared in this paper using biobased IS as the heat-resistant functional unit.…”

“…In our previous work, rigid polyester-polycarbonate was prepared by shielding the terminal hydroxyl groups with excellent results. 39 Therefore, the green and efficient polymerization method based on the excess of −OCH 3 groups was used to alleviate the negative impact of IS and a series of PCCITs were prepared in this paper using biobased IS as the heat-resistant functional unit.…”

“…The chemical shift at 4.65, 4.53, 4.44, and 4.32 ppm are related to the −CH 2 − groups (7c), (7t), (7′c), and (7′t) in the CHDM unit and its chemical structure from 1.00 to 2.6 ppm has been analyzed in our previous work. 39 The molar content of DMC and IS is determined using the eqs S1 and S2. Their relative integral areas were used to calculate the sequence distribution, number-average sequence length (L), and degree of randomness (R) based on the amounts of the CHDM and IS units.…”

“…The randomness based on IS (R I ) is obtained using the following eqs S3−S7. 39 The randomness based on CHDM (R C ) is also calculated. The detailed calculations are listed in eqs S8−S12.…”

“…In advance of the present study, we explored and used the end hydroxyl shielding method to prepare a series of rigid polyester-polycarbonates based on 1,4-cyclohexanedimethanol (CHDM), which provides a feasible synthesis route for rigid monomers with complex structures. 39 Due to the rigid structure of the nonplanar six-membered ring, the heat resistance of polyester-polycarbonate has been significantly improved, but its glass transition temperature still needs to be further enhanced. Copolymerizing molecules with rigid structures is one of the most direct and effective ways to improve heat resistance.…”