Maximum zero-field coupling

The quantity e qQlh, termed the quadrupolar coupling constant, is a function of the chemical environment of the deuteron. For example, in hexane e qQlh = 168 kHz (Burnett and Muller, 1971). Note that this quantity is independent of the magnetic field strength. NMR doublets are centered about the Larmor frequency, but in practice this frequency is subtracted away, so spectra are generally shown plotted as a function of frequency, centered on zero. The minimum observed frequency is v jn = -3l4 e qQ/h), and the maximum is = 3l4(e qQlh). (A very readable quantitative introduction to NMR studies of nuclei having quadrupole moments is given by Cohen and Reif, 1957). 

Output stress varies quadratically with electric field however, due to the inherent compliance of the materials, the force that can be coupled to a load will decrease with increasing strain for a particular electric field. Maximum force is available at zero strain and at maximum strain the elastomer will not generate any output forces. Note also that for a given strain, the output force, and thus the stiffness, can be modulated by varying the applied field. This is an important feature for artificial muscle applications as it allows the DE actuators to brace themselves as natural muscles do to maintain stability or prevent damage. 

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