In Situ Poling and Imidization of Amorphous Piezoelectric Polyimides

An amorphous piezoelectric polyimide containing polar functional groups has been developed using a combination of experimental and molecular modeling for potential use in high temperature applications. This amorphous polyimide, (I3-CN)APB/ODPA, has exhibited good thermal stability and piezoelectric response at temperatures up to 1500C. Density functional calculations predicted that a partially cured amic acid (open imide ring) possesses a dipole moment four times larger than the fully imidized closed ring. In situ poling and imidization of the partially cured ([_-CN)APB/ODPA was studied in an attempt to maximize the degree of dipolar orientation and the resultant piezoelectric response. A positive corona poling was used to minimize localized arcing during poling and to allow use of higher poling fields without dielectric breakdown. The dielectric relaxation strength, remanent polarization, and piezoelectric response were evaluated as a function of the poling profile. The partially cured, corona poled polymers exhibited higher dielectric relaxation strength (dc), remanent polarization (Pr) and piezoelectric strain coefficient (d33) than the fully cured, conventionally poled ones.

[1]  Zoubeida Ounaies,et al.  Structure-property study of piezoelectricity in polyimides , 1999, Smart Structures.

[2]  J. O. Simpson,et al.  Polarization and Piezoelectric Properties of a Nitrile Substituted Polyimide , 1996 .

[3]  I. Seo.  Piezoelectricity of vinylidene cyanide copolymers and their applications , 1995 .

[4]  P. Kollman,et al.  A well-behaved electrostatic potential-based method using charge restraints for deriving atomic char , 1993 .

[5]  A. Becke.  Density-functional thermochemistry. III. The role of exact exchange , 1993 .

[6]  Norman L. Allinger,et al.  Molecular mechanics. The MM3 force field for hydrocarbons. 1 , 1989 .

[7]  C. Pryde,et al.  IR studies of polyimides. I. Effects of chemical and physical changes during cure , 1989 .

[8]  T. Furukawa,et al.  Piezoelectricity and pyroelectricity in polymers , 1988, 6th International Symposium on Electrets,(ISE 6) Proceedings..

[9]  I. Seo,et al.  Large Dielectric Relaxations in an Alternate Copolymer of Vinylidene Cyanide and Vinyl Acetate , 1986 .

[10]  S. Miyata,et al.  Piezoelectricity and enthalpy relaxation in the copolymer of vinylidene cyanide and vinyl acetate , 1983 .

[11]  Seizo Miyata,et al.  Piezoelectricity Revealed in the Copolymer of Vinylidene Cyanide and Vinyl Acetate , 1980 .

[12]  H. Nalwa,et al.  Thermally stimulated currents in thiourea formaldehyde polymers , 1979 .

[13]  P. C. Hariharan,et al.  The influence of polarization functions on molecular orbital hydrogenation energies , 1973 .

[14]  H. Kawai,et al.  The Piezoelectricity of Poly (vinylidene Fluoride) , 1969 .

[15]  Errol Lewars,et al.  Computational chemistry , 2003 .

[16]  J. Harrison,et al.  POLARIZATION STABILITY OF AMORPHOUS PIEZOELECTRIC POLYIMIDES , 1999 .

[17]  A. Becke.  Density-functional thermochemistry. , 1996 .