Poly ionic field effects

Strong electron-donors or acceptors can effect charge transfer with insulating polymers and produce some increase in conductivity, e.g. from 10" S cm to 10" -10" Scm" for PS films exposed to iodine. This can be attributed to carrier hopping between localized charge-transfer sites, e.g. the pendant groups. The effect of organic and ionic impurities is particularly important in polymer films used as insulation and protective layers in semiconductor devices. This has been studied for various poly(ester imide)s by measurement of the residual current in a field-effect transistor (FET) coated with impurity-doped polymer. ... 

Ambient temperature molten salt can be obtained by several methods. One effective way to obtain a room-temperature molten salt is by the introduction of polyether chains to ions. The term polyether/salt hybrid is used in this chapter as a common name for polyether oligomers having anionic or cationic charge(s) on the chain (Figure 22.1). Polyethers, such as poly-(ethylene oxide) (PEO), are known as representative ion conductive polymers [1]. Polyether/salt hybrids have been studied as a kind of room-temperature molten salt apart from the development of onium-type ionic liquids [2]. The preparation of ionic liquids consisting of metal ions has been one of the important goals in this research field. Polyether/salt hybrid derivatives give one such solution for this task. 

Figure 8.10 Origin of electroviscous effects (a) electrical double layer round a particle at rest, (b) distortion of the electrical double layer in a shear field, leading to the primary electroviscous effect, (c) trajectories of repelling particles caused by double-layer repulsion, leading to the secondary electroviscous effect, (d) effect of ionic strength (or pH) on the extension of a charged adsorbed poly electrolyte, causing a change of the effective diameter of the particle, and the tertiary electroviscous effect.

Another example is a recent study of confinement effects in ionomers carried out at W-band. Electronic Tx and T2 relaxation as a function of temperature was measured at W-band for spin probes localized at the interface between the ionic clusters and the polymer. Excellent angular selection W-band EPR which resolves x-, y-, and z-orientations of the nitroxides in the magnetic field allowed authors to probe electronic relaxation along those orientations while the sample remained macroscopically disordered. Based on these measurements of the electronic relaxation as a function of the nitroxide orientation, it was concluded that reorientation of these spin probes has clear uniaxial features. Moreover, evidence was presented that the dynamic constraints on the poly(isoprene) chains in the diblock copolymer propagate over the whole chain consisting of approximately 170 monomer units. 

Since the discovery by Winslow, many ER fluids have been proposed. The majority of these systems contain a small amount of water [54, 55]. This is because water-containing particle-suspension liquids exhibit very large shear stress when an external electric field is applied [56, 57]. Dispersates for water-containing systems use particles that contain an ionically dissociated group (see Table 1). Inoiganic gels such as silica [58, 59] and alumina [60], and crosslinked metallic salts of poly(acrylic acid) [61, 62] also show the ER effect. 

Figure 35 shows Ibc D-E hysteresis cbaracleristks of PU79 and poly (nonunethyleneurea) PU9 obtained from the current density-eieGtric field curve, whicb excludes the DC conduction current of the san les (19]. The value of remanent polarization (P,) is 200-440 mCfin at 90 which may Ik attributed to an apparent effect from ionic currents of impurities. The reproducibility of P, depends on the crystallinity and molecular orientatiao, but Ibc same D-E hysteresis loop can be obtained for more than 100 cydes... 

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