Polymers refraction indices

This is a simplification of the Lorentz-Lorenz equation. Looyenga showed that the expression (n2— 1 )/(n2 + 2) can, with high accuracy be approximated by the more simple expressions (n213 — 1) for the polymer refraction indices mentioned in Table 10.5, the differences vary from 2.9% (n = 1.35) to 8.8% (n = 1.654). 

The factor f reduces the oscillation amplitude symmetrically about R - R0, facilitating straightforward calculation of polymer refractive index from quantities measured directly from the waveform (3,). When r12 is not small, as in the plasma etching of thin polymer films, the first order power series approximation is inadequate. For example, for a plasma/poly(methyl-methacrylate)/silicon system, r12 = -0.196 and r23 = -0.442. The waveform for a uniformly etching film is no longer purely sinusoidal in time but contains other harmonic components. In addition, amplitude reduction through the f factor does not preserve the vertical median R0 making the film refractive index calculation non-trivial. 

Table I. Calculation of Polymer Refractive Index from Laser Interferometer Waveform during Oxygen RIE...

The full expression for the reflected intensity of a laser interferometer in a plasma/polymer/silicon system can be used to measure the polymer refractive index to within about 3 percent. 

Use of the differential refractometer detector is applicable to all polymers having refractive indices different from that of the solvent. However, a correction must be made if the polymer refractive index depends on molecular size, such as at very low molecular weights. 

The fringes are created by the rotation of the sample along an axis which is parallel to the fundamental beam polarization. Since many of the samples have strong absorptions at 3co, care was taken to include accurate measurements of both the polymer refractive index and absorption coefficient at 3m in the analysis. Failure to... 

Where (dn/dc)k is the polymer refractive index increment in the solvent mixture, dn/dk is the variation of the refractive index of the solvent mixture as a function of volumetric composition and (dn/dc) is the polymer refractive index increment after establishing dialysis equilibrium. 

Values of dn/dc have a nearly linear dependence on solvent refractive index, so that if values are not available in the solvent to be used it can also be determined by extrapolation from other solvent systems. If the polymer refractive index and the partial specific volume of the polymer in the solvent Vp are known, then dn/dc can be estimated by the Gladstone-Dale rule (2),... 

Previous results were used for computer simulation of optical properties of the fabricated structures. By substitution to the RSoft software of measured polymer refractive index and the structure surface profile the inside and output optical field distribution were calculated using beam propagation method. The calculated output optical field is given in Fig 20C. In addition, calculation proved that the effective refractive index for fundamental mode is approximately 1.6276 at 632.8 ran. The prepared multimode structure supported 30 modes at wavelength 632.8 ran. 

Besides mechanical properties, fillers change the optical and electrical properties, chemical and weathering resistance, flammability and density of polymers. In particular, most fillers destroy optical translucency, unless their refractive index (see Table 4.4) is the same as that of the polymer. Close agreement between the fibre and the polymer refractive index is required for translucency. Feldspar has a refractive index very similar to that of several polymers and so filled, translucent products can be obtained, but it is abrasive to processing equipment. 

Transmission Range of Optical Materials Transparency of Polymers Refractive Index of Polymers Dispersion of Optical Materials... 

A few universal (bulk property) detectors are of frequent use in hplc of polymers. Refractive index detector is limited to isocratic elution and is utilized primarily in sec. The same is true for the recently introduced density detector based on mechanical oscillator principle (B. Trathnigg in Ref 4). Evaporative light... 

The refractive index detector measures both polymers simultaneously see Figure 3.22 (90). Flowever, the sensitivity to each polymer differs, being a function of the difference between each polymer refractive index and the solvent. The values are summarized in Table 3.13 (90). This particular system is nearly three times more sensitive to the polystyrene. 

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