Refractive indices measurement

Solution Polymers. Acryflc solution polymers are usually characterized by their composition, solids content, viscosity, molecular weight, glass-transition temperature, and solvent. The compositions of acryflc polymers are most readily determined by physicochemical methods such as spectroscopy, pyrolytic gas—liquid chromatography, and refractive index measurements (97,158). The solids content of acryflc polymers is determined by dilution followed by solvent evaporation to constant weight. Viscosities are most conveniently determined with a Brookfield viscometer, molecular weight by intrinsic viscosity (158), and glass-transition temperature by calorimetry. 

Optical properties also provide useful stmcture information about the fiber. The orientation of the molecular chains of a fiber can be estimated from differences in the refractive indexes measured with the optical microscope, using light polarized in the parallel and perpendicular directions relative to the fiber axis (46,47). The difference of the principal refractive indexes is called the birefringence, which is illustrated with typical fiber examples as foUows. Birefringence is used to monitor the orientation of nylon filament in melt spinning (48). 

Water Content and Refractive Index. The water content of a hydrophilic contact lens is a determinant of other properties. The relationship of water content and Dk is discussed above. Water content in lenses is inversely related to refractive index (23), a key property for vision correction. A lens material with a higher refractive index refracts light to a greater degree, allowing more vision correction with a thinner material. The water content of a lens is generally determined gravimetricaHy or inferred from the relationship to refractive index, measured with a refractometer (24). 

The reaction mixture is heated and allowed to reflux, under atmospheric pressure at about 100°C. At this stage valve A is open and valve B is closed. Because the reaction is strongly exothermic initially it may be necessary to use cooling water in the jacket at this stage. The condensation reaction will take a number of hours, e.g. 2-4 hours, since under the acidic conditions the formation of phenol-alcohols is rather slow. When the resin separates from the aqueous phase and the resin reaches the requisite degree of condensation, as indicated by refractive index measurements, the valves are changed over (i.e. valve A is closed and valve B opened) and water present is distilled off. 

It is important to note that comparable information to that obtained from infra-red spectroscopy can in principle be obtained from refractive index measurements. It has been shown that for a transversely isotropic film, the relationship equivalent to 11(c) is... 

The amorphous orientation can also be obtained, following conventional procedures, by combining X-ray and refractive index measurements, assuming the additivity... 

Ross, K.F.A. Billing, E. (1957). The water and solid content of living bacterial spores and vegetative cells as indicated by refractive index measurements. Journal of General Microbiology, 17, 418-25. 

The theory of counterion condensation is implicit in Oosawa (1957) but the term was coined later (Imai, 1961). The phenomenon was demonstrated by Ikegami (1964), using refractive index measurements of the interaction between sodium and polyacrylate ions. It has since been confirmed for many mono-, di- and trivalent counterions and polyionic species (Manning, 1979). 

The next step in this study is to test this control algorithm on the actual laboratory reactor. The major difficulty is the direct measurement of the state variables in the reactor (T, M, I, W). Proposed strategy is to measure total mols of polymer (T) with visible light absorption and monomer concentration (M) with IR absorption. Initiator concentration (I) can be monitored by titrating the n-butyl lithium with water and detecting the resultant butane gas in a thermal conductivity cell. Finally W can be obtained by refractive index measurements in conjuction with the other three measurements. Preliminary experiments indicate that this strategy will result in fast and accurate measurements of the state vector x. 

Ross and Billing, by means of refractive index measurements on spores and vegetative cells of B. cereus, B. cereus var. mycoides, and B. megaterium, found the values to be very high and comparable with that of dehydrated protein. This suggested that they contained much less water than the vegetative cells. 

Refractive index measurements indicated an adsorbance of 2 0.5 mg m 2 of the polymer onto the mica surfaces. 

Wei, T. Han, Y. Li, Y. Tsai, H. L. Xiao, H., Temperature insensitive miniaturized fiber inline Fabry Perot interferometer for highly sensitive refractive index measurement, Opt. Express 2008, 16, 5764 5769... 

The device has an all-glass structure and does not involve assembly of multiple components. As a result, we expect that the device will have very small temperature dependence. In addition, the open micronotch FP cavity allows prompt access to gas or liquid samples for direct refractive index measurement, making it possible to be used as an ultracompact chemical sensor based on refractive index measurement. 

To evaluate its capability for refractive index measurement, the fiber FPI device was tested using various liquids including methanol, acetone, and 2-propanol at room temperature. The interference spectra of the device immersed in various liquids are shown in Fig. 7.12 for comparison. The signal intensity dropped when the device was immersed in liquids as a result of the reduced refractive index contrast and thus lowered Fresnel reflections from the cavity endfaces. However, the interference fringes maintained a similar visibility. The spectral distance between the two adjacent valleys also decreased, indicating the increase of refractive index of the medium inside the cavity. Using (7.4), the refractive indices of the liquids were calculated to be nmethanoi = 1 -3283, acetone = 1 -3577, and n2-propanoi = 1.3739, which was close to the commonly accepted values. 

These interferometers have been demonstrated for refractive index sensing. The sensitivity was around 33 nm spectral shift per RIU change when they were used for refractive index measurement. The maximum fringe visibility of these interferometers was around 9 dB, which was relatively small compared with the interferometers constructed by other methods. 

Results of refractive index measurements for PMMA and VMCH during oxygen RIE at 35mTorr and various incident RF power densities are tabulated in Table I. The values in the first column are those... 

Refractive index measurements made by this technique are of sufficient accuracy to make this a valuable research tool in studying and characterizing the dry etch behavior of novel polymer resist materials. In situ etch rate can be measured and analyzed quickly without any prior knowledge of the polymer s physical properties. 

The temperature is important in refractive index measurements since the refractive index generally decreases with temperature. To maintain the sample at a constant temperature, temperature-controlled water is circulated around the prisms. 

Part D Percent Sugar in Soft Drinks by Refractive Index Measurements... 

Flow patterns of hydrodynamic systems like the compendial dissolution apparatus may be qualitatively characterized by means of dilute dye injection (e.g., methylene blue) or by techniques using particulate materials such as aluminum powders or polystyrene particles. Flow patterns may be also visualized by taking advantage of density or pH differences within the fluid stream. The Schlieren method, for instance, is based on refraction index measurement. Hot wire anemo-metry is an appropriate method to quantitatively characterize flow rates. The flow rate is proportional to the cooling rate of a thin hot wire presented to the stream. Using laser Doppler... 

Automatic specific gravity and refractive index measurement 200... 

AUTOMATIC SPECIFIC GRAVITY AND REFRACTIVE INDEX MEASUREMENT... 

The sample size required depends on the viscosity of the sample, the cell size of the density measurement device and the refractive index instrument. The density measurement requires a sample size of about 7-10 ml and the measurement must be made after a stabihzation period with no flow. In contrast, the refractive index measurement is made on a flowing stream. 

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