Sustainable aromatic polyesters with 1,5-disubstituted indole units

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Synthesis

Background:

• Indole-based aromatic polyesters are explored for their unique properties.
• Disubstitution patterns significantly influence polymer characteristics.
• Previous studies focused on 1,3-disubstituted indole structures.

Purpose of the Study:

• To investigate the effect of 1,5-disubstitution patterns on indole-based polyesters.
• To synthesize and characterize novel AB-type monomers and their corresponding polyesters.
• To evaluate the thermal stability, glass transition temperature, and crystallization behavior.

Main Methods:

• Synthesis of hydroxyl-carboxylate (AB-type) monomers with 1,5-disubstituted indole.
• Bulk polycondensation to form polyesters.
• Differential Scanning Calorimetry (DSC) and Wide-Angle X-ray Diffraction (WAXD) for thermal and structural analysis.
• Crosslinking studies using aromatic aldehydes.

Main Results:

• Polyesters derived from 1,5-disubstituted indole monomers exhibited enhanced thermal stability compared to 1,3-disubstituted analogs.
• Tunable glass transition temperatures (Tg ≈ 57-80 °C) were observed, dependent on methylene unit length.
• Polymers did not crystallize from the melt, but those with 3 or 5 methylene units crystallized from solution.
• Crosslinking with aromatic aldehydes improved thermal properties.

Conclusions:

• The 1,5-disubstitution pattern in indole-based polyesters offers superior thermal stability.
• Monomer design allows for tuning of glass transition temperatures.
• Solution-crystallization is achievable for specific polymer structures.
• Sustainable crosslinking provides a route to enhance thermal performance of these polyesters.