Liquid parallel-plate sample cells

Cell Construction. The optical interference technique to be used here is a modification of that described by Gramsbergen and de Jeu. This method uses a thin paraUel-plate cell containing a planar aligned nematic liquid crystal sample. The sample cell consists of two parallel 15 X 50 mm microscope slides separated by a gap D in the range 50-100 /zm, which is determined by spacer shims. A description of its construction is given below. 

An interferometer is an apparatus used to measure the refractive index of a gas or liquid. Light from a slit is rendered parallel by means of a collimating lens and then passed through two slits in front of a sample cell and a reference cell. A second lens focuses these two beams on a plate. 

All details of the pure continents relative molecular mass and rheology, and experimental setup of the ear cell are in reference (5). PIB and PDMS samples behave as Newtonian liquids under the experimental conditions hoe with shear viscosities of 10 Pa-s each (25 °C). The gap width between parallel plates in the Linkam CSS-450 shear cell was consistently set to 36 pm (standard uncertainty 3 pm verified optically by microscope stage translation), with all observations in the vorticity-flow plane. 

Yasuda et al. performed dielectric relaxation measurements on metastable solid MBBA, using a parallel-plate capacitor. Glass plates with strips of transparent tin-oxide-conducting coating served as electrodes. The cell was mounted in a copper beryllium pressure vessel, pressurized with liquid isopentane. A similar setup was used for the study of ferroelectric liquid crystals. Ferroelectric liquid crystals have also been studied by Chandrasekhar and co-workers who used a sapphire cell setup in a high-pressure apparatus. The sample was sandwiched... 

There are many designs of rheometer for materials with different viscoelasticities. For example, liquids can be examined in the Couette geometry, which consists of vertical concentric cylinders, one of which rotates with the sample between the gap. Cone-and-plate and parallel disc cells are also widely used. For soft solids, oscillatory shearing between vertical parallel plates yields the dynamic shear moduli. 

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