Isohexide and Sorbitol-Derived, Enzymatically Synthesized Renewable Polyesters with Enhanced T_g

Area of Science:

• Polymer Chemistry
• Green Chemistry
• Materials Science

Background:

• Development of sustainable polymers from renewable resources is crucial.
• Sugar-based polyesters offer potential as alternatives to petroleum-based plastics.
• Enhancing thermal and mechanical properties of bio-based polyesters is an ongoing challenge.

Purpose of the Study:

• To synthesize sugar-based polyesters using solvent-free enzymatic catalysis.
• To investigate the effect of incorporating rigid isohexide units (isomannide and isoidide) on polyester properties.
• To evaluate the performance of these polyesters in solvent-borne coatings.

Main Methods:

• Lipase-catalyzed polycondensation of sorbitol with isohexide derivatives (isomannide and isoidide dimethyl ester) under solvent-free conditions.
• Characterization of polyester thermal properties, including glass transition temperature (T_g).
• Preparation and evaluation of solvent-borne coatings by cross-linking polyester polyols with polyisocyanates.

Main Results:

• Sugar-based polyesters with pendant hydroxyl groups and rigid bicyclic isohexide units were successfully synthesized.
• Incorporation of isohexides significantly enhanced the glass transition temperature (T_g) compared to sorbitol-only polyesters.
• Polyesters derived from isoidide diester showed a more flexible character, while isomannide incorporation led to greater rigidity.
• Coatings formulated with these sugar-based polyester polyols exhibited improved hardness due to increased polyester rigidity.

Conclusions:

• Enzymatic catalysis provides a viable route for synthesizing functional sugar-based polyesters.
• Isohexide units effectively enhance the thermal stability and rigidity of the polyester backbone.
• These bio-based polyester polyols are promising building blocks for high-performance, sustainable coatings.