Polyimides (PIs) represent one of the most important classes of specialty polymers. They have found many applications in high performance films and fibers, coatings, microelectronics, optoelectronics, adhesives, aerospace structures, nonlinear optical devices, light-wave guiding materials, and liquid crystal displays. Polyimides containing benzonitrile units have been studied for the piezoelectric and other dielectric applications due to the high polarity of nitrile groups. In our previous research, one unsymmetric and two symmetric diamines as well as the respective polyimides containing benzonitriles were synthesized. Introduction of the unsymmetrical structures improved the processibility of poly(amic acids) (PAAs) and increased the PI dielectric constants while the dielectric loss was low. As a continuing effort to probe the structural factors to balance the need for high dielectric constant, low dielectric loss, and thermal stability in high temperature capacitors, polyimides containing three benzonitrile groups were synthesized. Thus, diamines containing three benzonitriles were synthesized via a 3-step route. They were polymerized with four commercial dianhydrides in DMAc to afford poly(amic acid) solutions, which were thermally cured up to 300 �C to form tough, creasable films. Most of polyimides are soluble in common solvents. Their glass transition temperatures range from 216 to 305 �C. The polyimides are stable up to 400 �C. The dielectric constants of these polyimides increased from 2.9 (CP2) to 4.3 (6FDA-based polyimide) at 10 Hz.

Synthesis and characterization of polyimides containing multi-benzonitrile groups for dielectric applications

245th National Meeting (2013)

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