Terephthalate Copolyesters Based on 2,3-Butanediol and Ethylene Glycol and Their Properties

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Polymers

Background:

• Traditional polyesters like PET face limitations in thermal properties and crystallinity.
• There is a growing demand for sustainable, biobased alternatives in polymer science.
• 2,3-butanediol (2,3-BDO) is a biobased diol with potential for modifying polyester properties.

Purpose of the Study:

• To synthesize and characterize novel terephthalate-based copolyesters incorporating varying ratios of 2,3-butanediol (2,3-BDO) and ethylene glycol (EG).
• To investigate the impact of 2,3-BDO incorporation on molecular weight, thermal properties (glass transition temperature, T_g), crystallinity, permeability, and tensile properties.
• To evaluate the potential of 2,3-BDO as a sustainable building block for advanced polyesters.

Main Methods:

• Synthesis of copolyesters via polycondensation of terephthalic acid derivatives with mixtures of 2,3-BDO and EG.
• Characterization using techniques to determine molecular weight (M_n), glass transition temperature (T_g), and tensile properties.
• Measurement of water and oxygen permeability to assess barrier properties.

Main Results:

• Copolyesters with up to 78% 2,3-BDO were synthesized, achieving molecular weights up to 31.5 kDa.
• Increasing 2,3-BDO content raised the glass transition temperature (T_g) from 88 °C to 104 °C.
• Water and oxygen permeability significantly increased with higher 2,3-BDO content, exceeding PET performance even at low concentrations. Tensile properties remained comparable to PET.

Conclusions:

• 2,3-butanediol can be incorporated into terephthalate polyesters to increase T_g and reduce crystallinity.
• Challenges remain in achieving high molecular weights with high 2,3-BDO content due to the lower reactivity of secondary diols.
• Despite increased permeability, 2,3-BDO offers a sustainable route for polyesters with tailored thermal and crystalline properties.