Radical Polyesters: Connecting Spacer Structure to Bulk Electrical Conductivity

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Electronics

Background:

• Electron exchange in polymers with radical sites enables applications in spin electronics and memory devices.
• Understanding how polymer structure, specifically spacer groups, affects charge transfer is crucial for optimizing these materials.

Purpose of the Study:

• To investigate the impact of different spacer structures within radical polyesters on bulk redox charge transfer.
• To determine the primary factors governing charge transport in these functional polymers.

Main Methods:

• Synthesis of TEMPO-functional radical polyesters via ring-opening copolymerization with varying anhydride comonomers.
• Characterization using SQUID magnetometry, EPR spectroscopy, density functional theory (DFT) calculations, and solid-state electrical conductivity measurements.

Main Results:

• Polyesters with 86-98% radical content were synthesized, with sulfur-containing polymers showing radical quenching.
• DFT calculations indicated rigid aromatic spacers bring radical sites closer than flexible aliphatic spacers.
• Electrical conductivity was found to be primarily dependent on the glass transition temperature, irrespective of spacer type or polymer architecture.

Conclusions:

• Spacer structure influences radical site proximity but not the overall charge transport efficiency.
• The glass transition temperature is the dominant factor controlling bulk charge transport in these radical polyesters.
• These findings provide insights for designing advanced polymer materials for electronic applications.