Measurement of the pyroelectric response and of the thermal diffusivity of microtomized sections of 'single crystalline' ferroelectric liquid crystalline elastomers

Abstract

The pyroelectric response and the thermal properties of microtomized sections of 'singlecrystalline' ferroelectric liquid crystalline elastomers (FLCE) have been investigated. The microtomized sections were manufactured in the thickness range from 20 to 100 mm. The roughness of the surfaces due to the cutting process was investigated with an alpha-stepper and found to be in the range of about 5 mm. The thermal di usivity of the elastomer at di erent temperatures was determined by placing the sample on a pyroelectric substrate and measuring the pyroelectric signal of the substrate under appropriate conditions. From the pyroelectric current spectra, information about the spatial distribution of the polarization could be deduced. It was found to be constant except in a range also about 5 mm near the surface. From the combination of this result and that of the alpha-stepper measurements, the conclusion is drawn that the molecular orientation at the surface is destroyed due to the cutting process. The magnitude of the spontaneous polarization was calculated from the pyroelectric measurements at di erent temperatures, making use of the thermal di usivity values.

Artificial Muscle Technology: Physical Principles and Naval Prospects

“…The quantity ipC^'^ is known as the thermal difEiisivity. Leister et al [33] measured the thermal diffiisivity for a ferroelectric liquid crystalline elastomer with a polysiloxane backbone and found values of 2 x 10"* to 4 x 10"* m^/s. For a flat film with a thickness of 100 [xm, the corresponding time constant is between 0.25 and 0.5 s. The rate is expected to be proportional to the inverse square of thickness, so it should be possible to activate a 1 fim thick film in less than 100 |xs.…”

Measurement of the polarization profile across a surface-stabilized ferroelectric liquid crystal cell using the pyroelectric laser-intensity-modulation method

“…It was found, however, that the model given by Leister et al 9 gives the most reliable results for the deconvolution of the experimental data using the regularization procedure…”

“…We have examined an applicability of several thermal models to our case, some of these are described in the literature, 8,9,11 and these were applied to the geometry of the liquid crystal cell. It was found, however, that the model given by Leister et al 9 gives the most reliable results for the deconvolution of the experimental data using the regularization procedure…”

“…Recently this pyroelectric method was applied for studying the ferroelectric liquid-crystalline elastomers. 9 The principle of the LIMM is as follows. [8][9][10][11] An intensity-modulated laser beam irradiates an opaque electrode of a sample.…”

“…9 The principle of the LIMM is as follows. [8][9][10][11] An intensity-modulated laser beam irradiates an opaque electrode of a sample. Absorption of the laser light in the electrode produces thermal waves that extend into the sample which cause the pyroelectric response; this is a convolution of the pyroelectric coefficient distribution and the temperature profile across the sample.…”