Constructing Novel High Dielectric Constant Polyimides Containing Dipolar Pendant Groups with Enhanced Orientational...

Area of Science:

• Polymer Science
• Materials Science
• Dielectric Materials

Background:

• High dielectric constant polymers are crucial for electrical and pulsed power applications.
• Designing polymers with dipolar side chains enhances dielectric properties and reduces loss.
• Novel polyimides with urea, carbamate, and sulfonyl groups were synthesized for comparison.

Purpose of the Study:

• To synthesize and compare dielectric properties of novel polyimides with urea, carbamate, and sulfonyl side chains.
• To investigate the relationship between side chain structure and dielectric performance.
• To evaluate the potential of these polymers in energy storage applications.

Main Methods:

• Synthesis of novel polyimides with urea (BU-PI), carbamate (BC-PI), and sulfonyl (BS-PI) functional groups.
• Comprehensive dielectric property characterization using dielectric spectroscopy.
• Evaluation of energy storage performance, including discharged energy density and charge-discharge efficiency.

Main Results:

• Polyimides with dipolar side chains exhibited high dielectric constants and low dielectric loss.
• BU-PI, containing urea pendant groups, showed the highest dielectric constant (6.14) and low dielectric loss (0.0097).
• Dielectric spectroscopy revealed strong γ transitions and enhanced free rotational motion of urea dipoles.
• BU-PI achieved a discharged energy density of 6.92 J cm^-3 and >83% efficiency at 500 MV m^-1.

Conclusions:

• Urea pendant groups provide superior dielectric properties in polyimides compared to sulfonyl groups.
• The enhanced orientational polarization and suppressed dipole-dipole interactions contribute to improved dielectric performance.
• These novel polyimides, particularly BU-PI, are promising for advanced energy storage and electrical applications.