Refractive index of polymers

Methyl- and 3-ethylsydnone have been used as aprotic solvents for electrolytes <2000MI20, 2002MI334>, whereas 3-phenylsydnone has been employed as a filter for recording the absorption spectra and refractive indexes of polymer films containing other mesoionic compounds <2002MI2290>. 

When a differential refractometer is used as a detector, instrumental broadening of the GPC chromatogram is compensated to some extent by another effect due to the tendency for specific refractive indexes of polymer solutions to decrease with decreasing molecular weight in the low-molecular-weight range. 

Experimental. The differential refractive indexes of polymer solutions were measured at 25°C with a Waters Scientific R-403 differential refractometer connected on-line with a size exclusion chromatograph. The refractometer was calibrated to refractive index units (Riu) with benzene/carbon tetrachloride solutions. The rationale behind using the refractometer on-line with the chromatograph is the elimination of impurities in the sample (water, residual monomer etc.) which affect the refractive index measurements particularly at low polymer concentrations and to calibrate the detectors at the flow conditions at which they were normally operated. Polymer solutions of several concentrations (0.015-0.0025 wt %) were injected repeatedly to verify the reproducibility of the measurements, which was typically An 0.5 x 10-6 for replicates on the same solutions. 

An important technological property of polymers is the glass transition temperature (Tg), that is the temperature at which an amorphous polymer is transformed, in a reversible way, from a viscous or rubbery condition to a hard and relatively brittle one in the vicinity of Tg, a polymer experiences a sudden increase in the rate of molecular motions and, as a result, undergoes a series of conformational transformations. Another important polymer technological property is the refractive index of polymers, whose high values are usually related to highly conjugated, aromatic type, 7i-electron systems that bear heavy elements such as bromine or iodine. 

Holder, A.J., Ye, L., Eick, J.D. and Chappelow, C.C. (2006a) A quantum-mechanical QSAR model to predict the refractive index of polymer matrices. QSAR Comb. Sci., 25, 905-911. 

Table 8.4. Comparison of the molar refraction according to Lorentz and Lorenz (Rj j) calculated by using group contributions for organic liquids, with RLL values calculated from the new correlations developed in this manuscript for the molar volume and the refractive index of polymers at room temperature, for 100 polymers. V(new) and n(new) are the molar volumes and refractive indices, respectively, calculated by using the new correlations. Ru new) can be calculated for all polymers, without any need for group contributions. 

Since all compounds refract light, the RI is known as a universal detector. It is the most widely used detector to monitor the MWD. The refractive index of polymers is constant above approximately 1000 Da. Therefore, the detector response is directly proportional to the concentration. 

The two measurement methods recommended by IS0489 are the Abbe refractometer technique and the Becke line technique. The latter is more useful with powdered or granulated transparent material or even with small chips of material taken from a larger sample. ASTM D542 includes only the Abbe method and it is widely used for characterization of refractive index of polymers. 

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

Problem 3.11 DLS measurement is conducted for a dilute ternary solution of two different polymers a and b in a non-selective solvent. The two polymers are dissolved at concentrations and c, . The differential refractive index of polymer a in the solvent is dn/dc and that of polymer b is dn/dc. We assume that the two polymers are monodisperse with molecular weights and Mb, and the decay rates in gi(T) measured for a binary solution of polymer a (i.e., polymer a -l- the same solvent) and another binary solntion of polymer b are and Fb, respectively. Find the apparent distribution G(F) for the ternary solution. What is gi(T) for the solution Assume that the two polymers are molecularly dispersed in the ternary solution. 

Refractive index of polymers/haze value (Continued)... 

The refractive index of polymers provides fundamental information that can be used in the analysis of parts, processing, and characterization. It has been demonstrated that the square of refractive index is related to the dielectric constant of a polymer, both in direction and magnitude.Table 13.43 shows the values of the refractive index of fluoroplastics, measured at a light wavelength of589.3 nm and referred to as > in literature. 

Light-scattering is a function of refractive and diffractive mechanisms. The particles are too small to diffract visible light. The refractive index of clay is very close to the refractive index of polymers utilized in packaging. 

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