Electric-field-sensitive polymers

Figure 10.4 Structures of polymers and polymeric drug delivery systems sensitive to light and electric fields, (a) Light-sensitive polyamidoamine dendrimes conjugated with doxorubicin via photo-cleavable ortho-nitrobenxyl linkages (Choi et al., 2010). (b) Electric-field-sensitive (Wood et al., 2008).

Filipcsei, G., Feher, J. and Zrmyi, M. (2000) Electric field sensitive neutral polymer gels . Journal of Molecular Structure, 554,109-117. 

English AE, Edelman ER, Tanaka T (2000) Polymer hydrogel phase transitions. Chapter 6. In Tanaka T (ed) Experimental methods in polymer science. Academic, Boston, pp 547-589 Filipcsei G, Feher J, Znnyi M (2000) Electric field sensitive neutral polymer gels. J Mol Stmct 554 109-117. doi 10.1016/S0022-2860(00)00564-0 Flory PJ (1942) Thermodynamics of high polymer solutions. J Chem Phys 10 51-61. doi 10.1063/ 1.1723621... 

In order to avoid interchain entanglements, it is essential experimentally to keep the polymer concentration in the matrix very low. Upon volatilization of the matrix, the polymer species are desorbed and ionized (by a mechanism still ill-known), which makes them sensitive to the accelerating effect of an electric field. For polymer analysis, the positive mode—the one which causes the formation of a positive charge on the chain by interaction with a cationic species (proton or metal cation)—is generally used. 

Disadvantages associated with some organic solvents include toxicity flammabiHty and explosion ha2ards sensitivity to moisture uptake, possibly leading to subsequent undesirable reactions with solutes low electrical conductivity relatively high cost and limited solubiHty of many solutes. In addition, the electrolyte system can degrade under the influence of an electric field, yielding undesirable materials such as polymers, chars, and products that interfere with deposition of the metal or alloy. 

The model of electric field-controlled artificial muscles has been described in 1972 [5], Fragala et al. fabricated an electrically activated artificial muscle system which uses a weakly acidic contractile polymer gel sensitive to pH changes. The pH changes are produced through electrodialysis of a solution. The response of the muscle as a function of pH, solution concentration, compartment size, certain cations, and gel fabrication has been studied. The relative change in length was about 10%, and the tensile force was 1 g/0.0025 cm2 under an applied electric field of 1.8 V and 10 mA/cm2. It took 10 min for the gel to shrink. 

Experimental and theoretical results are presented for four nonlinear electrooptic and dielectric effects, as they pertain to flexible polymers. They are the Kerr effect, electric field induced light scattering, dielectric saturation and electric field induced second harmonic generation. We show the relationship between the dipole moment, polarizability, hyperpolarizability, the conformation of the polymer and these electrooptic and dielectric effects. We find that these effects are very sensitive to the details of polymer structure such as the rotational isomeric states, tacticity, and in the case of a copolymer, the comonomer composition. 

It was pointed out earlier that photosensitivity may be realized not only by the inclusion of dyes in a polymer matrix, but also by means of multilayered system production. For TPA dispersed in a polycarbonate, sensitized by a thin layer of vacuum-deposited amorphous selenium, the quantum yield was equal to 0.7 at the electric field strength 6 x 10s V cm-1 [308]. The photoinjection efficiency of holes into polymer was equal to the efficiency in pure selenium. The spectra of the quantum efficiency is shown in Fig. 54. 

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