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KEY WORDSPolyurea / Ferroelectricity / Hydrogen Bonding / Remanent Polarization / Pyroelectricity / Recently, Polyureas are attracting much attention in the fields of electronics and photonics. Polyureas with large dipole moments (4.5D) of -NHCONH show strong pyroelectric 1 and ferroelectric behavior. 2 The molecules in most polyureas are generally aggregated by a strong hydrogen bonding of NH· · 0 = C to induce unusual properties. It is of great interest to study the roles of hydrogen bonding in connection with electrical properties.The N-phenylated aromatic polyurea used in this study, synthesized by reacting an equimolar mixture of diamino-p-xylene with 4,4'-diphenylmethane diisocyanate, forms flexible and transparent films and exhibits a large second-order nonlinear optical coefficient after poling. 3 • 4 These properties seem to arise from the chemical structures of polymers. The lower density of hydrogen bonding introduced by N-substituted structure and bulky main chain are responsible for an amorphous structure. Though it is easy to form polar structures of polymers with hydrogen bonding, not to realize a ferroelectric structure. However, if one polymer chain can obtain a polar chain structure without an strong aggregate moiety such as hydrogen bonding, the resulting bulk structure would be ferroelectrics by controling the external electric field.This communication discusses the possibility of amorphous ferroelectrics for polyurea systems having a small amount of hydrogen bonding.Polyurea prepared by the method as described earlier 3 was cast into thin film (5 µm) from a chloroform solution at room temperature. Thin film samples metalized by aluminum evaporation on both sides were subjected to the polarization reversal measurement. Dielectric measurements were carried out under vacuum with a HP 4285 LCR meter. Displacement-field (D-E) curves were generated from the I-V data obtained by measuring the current through the electrode area in response to a triangular voltage input with a frequency of 0.01 Hz. Thermally stimulated depolarization current (TSC) for poled samples was recorded at a heating rate of 4°C min -1 . IR spectra for the polyurea film were recorded on a JASCO FT/IR3 spectrometer.Dielectric measurement performed on thin 505

Plasma polymerizations of bis(dimethylamino)methylsilane (BDMAMVS), bis(dimethylamino) methylvinylsilane (BDMAMVS), and trimethylsilyldimethylamine (TMSDMA) were investigated by elemental analysis, IR spectroscopy, and ESCA. Polymer deposition was fairly faster in the BDMAMVS and TMSDMA systems than in the BDMAMS system, indicating that vinyl and methyl substituents contribute to polymer formation, whereas hydrogen substituents disturb the polymer formation. IR and ESCA spectra for these polymers showed that some dependence of the polymers formed in the chemical composition on the nature of the monomers. A part of methylamino groups in these monomers were oxidized to give amido and amine oxide groups. BDMAMVS and TMSDMA yielded polymers with few fragmentations of methylamino groups, whereas the polymers formed from BDMAMS had no methylamino groups.

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