Poled polar polymers

Poled polar polymers (ekulrct pulymexs) Polyvinyl chloride Polyacryloaiullc Polyvinyl flooridc Polarizatioa of oriented molecular dipoles Pru2cn-in polarization Ji] < 3... 

The birefringent (BR) modulator makes use of polarized light and tensorial nature of the electrooptic coefficient. For example, poled organic polymer films are characterized by two nonzero components for the electrooptic tensor and parallel and orthogonal to the poling direction,... 

Kawai (1) and (2) (1969) found that polar polymer films such as PVDF, poly (vinyl fluoride), PVC, nylon 11, and polycarbonate exhibit a strong piezoelectricity when they are drawn and then polarized under a high cLc. field Ep at a high temperature Tp and cooled keeping the d.c. field. The piezoelectricity thus obtained depends on Ep, Tp, and poling period. An improved poling technique was reported by Edelman, Grisham, Roth, and Cohen (1970). 

The bending piezoelectricity in drawn and polarized polymer films was studied in detail by Kawai (1) (1970). Kitayama and Nakayama (1971) reported a very high piezoelectricity in composite films of polymer (PVDF, nylon 11, PVC) and powdered ceramics (barium titanate, PZT) after poling. In the case of PVDF and nylon, the piezoelectric constant increase by a factor of 102 when the ceramics make up 50% of the volume. The pyroelectricity and optical nonlinearity of polarized PVDF films have been studied by Bergmann, McFee, and Crane (1971). 

This paper explores both electric field poling of polymers and LBK deposition of intrinsic y polar polymer films containing the chromophoie in the main-chain, or accordion architecture (3a). Mainchain syndioiegic polymers and poled films constitute the first topic, followed by a second section that describes a bilayer approach to intrinsically polar films. 

Piezoelectricity is a property whereby mechanical strain produces dielectric polarization and, conversely, an applied electric field produces mechanical strain. Piezoelectricity is exhibited by piezoelectric crystals, polarized polymers, and composites, and is utilized in a variety of electromechanical transducers. To induce piezoelectricity in certain ceramic crystals, one must apply a high dc field to switch the polar axis of the crystals to the symmetry allowed directions nearest to the applied field. This process is called poling. 

Bauer S, Bauer-Gogonea S, Ploss B, Ploss B (2005) Nonlinear dielectric response of poled amorphous polymer dipole glasses. J Non-Cryst Sol 351 2759—2763 Bauer-Gogonea S, Bauer S, Gerhard(-MuHhaupt) R (1999) Monomorphs, bimorphs, and multimorphs from polar polymer electrets. Braz J Phys 29 306-317 Broadhurst MG, Davis GT (1984) Physical basis for piezoelectricity in PVDF. Fenoelectrics 60 3-13... 

The application of high fields to charge or polarize polymer electrets inherently involves the risk of sample damage due to electrical breakdown. While local air breakdown in voids is part of the poling process, energy-rich discharges over large areas of ferroelectric polymers will lead to sample failure. 

The symmetry of CL, bolds for the pokd composite films consisting of piezoelectric ceramk powders and polymers. When dongaled films ot polar polymer ate poled, the symmetry of C> appears. The 3 axes for and Ci, ate in the directioo of poling. In 1969, Kawai first discovered large tensile piezoelectricity in elongated and poled films of polyfvinylidene fluoride) (11]. 

Whereas ferroelectridty in polymers of the polyfvinylidene fluoride) (PVDF) type b induced by stretching and poling of polymers films and b not chaiacteristk for undisturbed samples, spontaneous polarization appears in liquid crystalline polymers with intrinsic lower symmetry Cj. 

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