Piezoelectric properties of thin films of aromatic polyurea prepared by vapor deposition polymerization

Abstract

Aromatic polyurea films of a few hundred nanometer thickness were prepared by vapor deposition polymerization of the monomers 4,4′-diaminodiphenylmethane and 4,4′-diphenylmethane-diisocyanate. Piezoelectric activity was observed after poling the films under an electric field of 100 MV/m at 210 °C for 10 min. The piezoelectric stress constant (polarization/strain) remains constant at about 15 mC/m2 over the temperature range from −50 to 200 °C. The multilayer film produced by the alternate deposition of polyurea layers and aluminum electrodes exhibited a response proportional to the number of layers. The residual polarization caused by alignment of the dipoles of the urea bond is believed to be the origin of the effect.

Electric Double Layer Gate Field-Effect Transistors Based on Si

“…The observed difference may have come from the fact that the PU in the present experiment contains a large aromatic moiety and that the urea bond density of this PU is much lower than that of the simple aliphatic PU indicated in ref. 13.…”

“…Following the previous reports on the codeposited films [12][13][14] , we applied thermal treatment showing the completion of the polymerization reaction 13) . The optical transparency and surface morphology of the film did not change after the thermal treatment.…”

“…They are potentially applicable as key components of flexible memories [2][3][4][5][6] , transducers 7,8) , power sources 9,10) , and printable thermal sensors 11) . Polyurea (PU) has unique characteristics among the piezoelectric polymers because it can be fabricated by vapor deposition polymerization without by-products [12][13][14][15][16] . The high dipole moment (4.9 D) in its unit structure coming from the urea bond is also attractive because the strength of spontaneous polarization strongly depends on the dipole moment.…”

Low-Temperature Polymer Bonding Using Surface Hydrophilic Treatment for Chemical/Bio Microchips

“…8, the as-deposited polyurea film of only about five monomers (n = 5) is formed at room temperature (Wang et al, 1993). Further polymerization takes place (n > 5) when asdeposited films are annealed (without any surface treatment) by consuming the unreacted (Shinohara et al, 2009a) polymer tails to form amid bonds (Takahashi et al, 1991). These transformations or polymerization could also have occurred at the interface of the two polyurea films during the bonding process.…”

Atomistic simulations of aromatic polyurea and polyamide for capacitive energy storage

“…Polyureas have already been widely used in industry, in applications focusing on their great elasticity and strength. Moreover, aromatic polyureas have been reported to have sizable pyroelectric, piezoelectric and nonlinear optical properties more than a decade ago [15][16][17][18][19], suggesting their potential as capacitive dielectrics. All polymers in this family have functional groups with large dipole moments, i.e., urea, thiourea and amide, but they do not form a ferroelectric phase as PVDFbased materials do.…”