Poly piezoelectric activity

STRONG PIEZOELECTRIC ACTIVITY IN SIMULTANEOUSLY STRETCHED AND POLED POLY(VINYLIDENE FLUORIDE)... 

State of the Art. Pioneering work in the area of piezoelectric polymers (9) led to the development of strong piezoelectric activity in poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (TrFE) and tetrafluoroethylene (TFE). These semicrystalline fluoropolymers represent the state of the art in piezoelectric pol5uners and are currently the only commercial piezoelectric polymers. 

Studies of the unique piezo- and pyro-electric properties of poled poly(vinylidene fluoride) have made a fundamental understanding of origin of the properties the subject of intense activity.Central to this study is the structure determination of the four phases, I, II, III, and IV, and their interconversion to test the correlation between orientation, crystal structure, and activity. The greatest piezoelectric activity is found with phase I, produced by subjecting phase II, the normal form produced on melt crystallizing, to intense electric fields up to 5 x 10 V cm, i.e. poling. The activity has been attributed to bulk polarization of the poly(vinylidene... 

E J. Sbuford, A. F. Wil. J. J. Rkca, anid G. E Thomas. Characterization and piezoelectric activity of stretched and poled poly(vtnytidene fluorideX 7>tt I effect of draw ratio and poling conditions. Polymer Eng. Sci 16 2S (1976X... 

R. J. Shufonl. A. F. Wilde. J. J. Rkca. and G. R. Thomas, Oiaracterizarioo and piezoelectric activity of suctchcd and poled poly(vinylidene fluoride). L Effect of draw ratio and poling cooditioni. Polymter Eng. ScL I6-J5 (19W). 

This device employs single-stranded poly(adenylic acid) [poly(A)] as the chemical recognition agent. This species selectively recognizes its complementary polymer, poly(U), through hybridization to form a double-stranded nucleic acid. The poly(A) is immobilized onto the activated surface of a quartz piezoelectric crystal, which is a mass-sensitive transducer. Electric dipoles are generated in anisotropic materials (such as quartz crystals) subjected to mechanical stress, and these materials will... 

A review appeared on piezoelectric quartz crystals used as detectors for phenols in air, after coating with Triton X-100 and 4-aminoantipyrine (78), or with activated carbon cloth impregnated with various compounds, such as poly(vinyl pyrrolidone). A piezoelectric sensor was proposed for determination of trace amounts of phenol and alkylphenols in air. The problems attaining selectivity of the adsoption membranes and operating conditions were addressed . An AT-cut quartz crystal, coated with a hydrophobic PVC layer and operating in the thickness shear mode, has been used to detect 4-aminophenol, after conversion to a hydrophobic indophenol dye and adsorption on the polymer layer. The mode of preparation of the PVC coating affects the sensitivity of the detector , a... 

However, in addition to their thermoplasticity, representatives of PHAs have optical activity, increase induction period of oxidation, exhibit the piezoelectric effect and, what is most important, they are characterized as being biodegradable and biocompatible. At the same time, the PHAs have disadvantages (high cost, brittleness), which can be partially or completely compensated by using composite materials based on blends with other polymers, with dispersed fillers or plasticizers. Taking into account all the above, we have suggested to create a mixed polymer composite based on poly-3-hydroxybutyrate (PHB) and polyisobutylene (PIB). 

A schematic of fee QCM instrument is shown in Figure 1. Two QCM crystals are used in the experiments, so that detection is done in a differential mode. One is termed fee active crystal, which has hexokinase immobilized by entitqipment in a poly(acrylamide) gel. The other is termed the reference crystal, which has bovine serum albumin (BS A) immobilized in exactly fee same way. A similar differential mode technique, utilizing piezoelectric cystals, has been previously decribed using a... 

Electrical Stimuli. Electrically active materials have also been used to encourage tissue growth. The use of piezoelectric materials made of vinyUdene fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] enhanced peripheral nerve regeneration in vivo (Fine et al., 1991), and when PC12 cells were cultured on oxidized polypyrrole, the application of an electrical stimulus resulted in enhanced neurite extension (Schmidt et al., 1997), as shown in Fig. 16.3. Implant vascularization was enhanced when bilayer films of polypyrrole-hyaluronic acid and polypyrrole-poly(styrenesulfonate) were implanted subcutaneously (Collier et al., 2000). These types of electrical stimuli can be used in conjunction with a biomaterial to promote tissue regrowth. 

Poly(vinylidene chloride). The carbon-chlorine dipole in poly(vinylidene chloride) (PVDC) has been oriented to produce a low level of piezoelectricity. The piezoelectric and pyroelectric activities generated in PVDC are stable and reproducible. PVDC has been used as a basis for understanding and studying piezoelectricity in amorphous polymers (39). The piezoelectric coefficients dsi of PVDC are reportedly in the range of 0.5-1.3 pC/N. This response was improved by simultaneous stretching and corona poling of film (44). The enhanced piezoelectric coefficient dsi ranged from 1.5-5.0 pC/N (see Vinylidene Chloride Polymers (PVDC)). 

Lee et al. (2005) employed flie PEDOT/PSS treated with a dimethyl sulfoxide (DMSO) solvent as the electrodes of all polymer bimorph cantilevers in which the piezoelectric polymer poly(vinyUdene fluoride) (PVDF) was used as the active layers, as shown in Fig. 27. They compared flic mechanical output of the bimorph cantilevers with the PEDOT/PSS (DMSO) electrodes and that of the inorganic electrodes such as platinum (Pt) and indium tin oxide (TTO). The cantilever with... 

One active area of research is completely missing. These are the optical and electrical properties, with effects such as the high conductivity of doped conjugated polymers, electro-luminescence in polymeric light emitting diodes, or the ferro- and piezoelectricity of poly(vinylidene fluoride), to cite only a few examples. There is no good reason for this omission, only that I did not want to overload the book with another topic of different character which, besides, mostly employs concepts which are known from the physics of semi-conductors and low molar mass molecules. 

As synthesized, optically active polymer besides polypeptides, polypropylene oxide was first investigated for piezoelectric properties [40]. A film of poly-o-propyleoe oxide (PDPO) was cast from a benzene solution and elongated by about S0% of its original length. The degree of crystallinity was about 40%. 

Ihble 2 shows a comparison of physical quantities for three optically active polymers described above. With an increase of polarity in chemical structure, the magnitude of the piezoelectric constant increases remarkably, although the degree of crystallinity and the degree of orientation are not exactly the same for the three polymers. The chemical structure of poly-lactic acid is the simplest form to oou de an asymmetric carbon atom and a polar group CO-O and is most suitable for displaying the piezoelectric effect in this aeries. 

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