Refractive index increments of polyethylene

The refractive index increments of linear and branched polyethylene were determined for several solvents and various wavelengths (403, 436, 546, and 633 nm), mainly at 135°C. Differences were observed between values for linear and branched samples. Data obtained in this investigation are compared with the reported ones.     

Refractive index increments of di-n-alkylitaconate polymers and copolymers

Refractive index increments of 11 poly(di-n-alkylitaconate) polymers were determined systematically in seven organic solvents, expected to be suitable for light scattering and other solution property measurements. Of 13 solvents tried, poly(dimethylitaconate) was soluble only in 6, however higher members of the polymer series exhibit better solubility. The measured dn/dc values in butanone and ethyl-and amylacetate are practically independent of an increase of the number of carbon atoms in the ester substituents of the monomer, however a decrease of the values for solvents with higher refractive indices can be observed. For statistical poly(styrene-co-di-n-alkylitaconate) samples the additive character of dn/dc in butanone and toluene was observed and verified from copolymer compositions determined by UV and elemental analysis.     

Specific refractive index increments of segmented polyurethanes

Specific refractive index increments ν of polyester-based segmented polyurethanes in N,N-dimethyl formamide have been determined, and the quotient dν/df_d has been evaluated (where f_d is the weight fraction of hard-segment units). The results are in good agreement with the values calculated from group contributions to the molar refraction, using the Vogel or the Gladstone–Dale equations. The values calculated with the Lorenz–Lorentz equation are too low. A potential explanation of this fact is proposed. The same methods have been applied to reported ν values for polyether-based polyurethanes. An explanation is proposed for differences in dν/df_d for polyester- and polyether-based polyurethanes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1917–1923, 1998     

Refractive index of alcohol nonionics

Refractive index is a rapid and consistent method of analysis for alcohols and nonionics from normal alcohols and ethylene oxide. Correlations of refractive index with hydroxyl number of alcohols and nonionics are excellent and measurement error is considerably lower for refractive index. Refractive index affords a measurement of the amount of ethylene oxide in nonionics and can be used as a replacement for the 1% cloud point analysis. The ethylene oxide adduct distribution has no effect on refractive index. Specific adducts, a narrow range of adducts made by acid catalyzed ethoxylation and a broad range of adducts made by base catalyzed ethoxylation give the same refractive index value for any given ethylene oxide content. Applications for the refractive index method for the laboratory and plant are: alcohol blending control, calculation of ethylene oxide requirements for ethoxylation, nonionic control analysis, calculations of hydroxyl number for sulfations. Also, refractive index can help identify laboratory samples, indicate the 1% cloud point and predict the phase character of nonionics.     

Specific refractive index increments of certain polysaccharide systems

The specific refractive index increments of amylose, amylose acetate, amylopectin and glycogen in various aqueous and non-aqueous solvents have been determined. These were measured by the direct determination of deviation method.     

Specific refractive index increments of Guayule rubber in several solvents

The specific refractive index increments of Guayule rubber were determined in four solvents (hexane, chloroform, toluene and tetrahydrofuran) using two wavelengths (5461 and 4360 Å). The determinations took place at 25°C and the results were compared with those obtained in natural Hevea rubber and Natsyn. The values of υ obtained were Hevea > Guayule > Natsyn.     

Static measurements of refractive index increments at 633 nm with a modified refractive index detector

Summary A R 401 Waters Assoc. differential refractometer has been modified to obtain the variation of refractive index increments, dn/dc, of polymer solutions at 633 nm. The introduced modifications were in the sample injection system and in the light source. The performance of the modified refractometer both with aqueous and organic solutions is analyzed. In order to localize a conformational transition in lysozyme, the dependence of dn/dc on temperature for lysozyme solutions in phosphate buffer is studied. Similarly, (dn/dc)_k values for the ternary n-alkane/butanone/poly(dimethyl siloxane) systems over the whole composition range of the binary solvent mixtures are evaluated.     

一种煤基油窄馏分折射率计算方法研究

为了考察寿德清-向正为关系式计算煤焦油及焦油加氢产物窄馏分样品折射率的准确性,在通过分析大量样品和实验数据的基础上,对比了计算值与测定值之间的差异。结果表明:计算中低温煤焦油窄馏分样品的折射率时,样品的计算结果与测定结果相差较大,寿德清-向正为关系式不可直接用于计算煤焦油窄馏分折射率;用寿德清-向正为关系式计算两种焦油加氢产物窄馏分样品的分子量时,样品的计算结果与测定结果较接近,对焦油加氢产物B样品来说,两种方法的平均误差为0.27%,均方差为0.34%;对焦油加氢产物C样品来说,两种方法的平均误差为0.21%,均方差为0.32%。寿德清-向正为关系式可直接用于计算焦油加氢产物折射率。     

Refractive index tuning of highly transparent bismuth containing polymer composites

A new method for the preparation of transparent bismuth containing composites is reported. With the organic ligands 2,3-Dihydroxypropylmethacrylate (HMA) and 2-(Methacryloyloxy)-ethylacetoacetate (AcMA), bifunctional monomers with a functional group for metal complexation on the one hand and a reactive group for polymerization on the other hand were found. By integrating up to 20 wt-% bismuth in the monomer mixtures, an increase of the refractive index of 4.0% (?n = 0.058) is determined. The metal complexation was observed via infrared spectroscopy (AcMA) and NMR spectroscopy (HMA). Subsequent addition of trimethylolpropane triacrylate (TMPTA) as cross-linking agent and 2,4,6-trimethyl-benzoyldiphenylphosphine oxide (TPO) as photoinitiator to the bismuth containing monomers Bi-HMA and Bi-AcMA lead to a UV-curable liquid. Photoinduced polymerization was used to generate transparent bismuth containing hybrid materials with increased refractive index. The polymers were characterized by UV/VIS spectroscopy, ellipsometry and DTA/TG. The materials show a high transmission (>80% in 2 mm thick plates) in the visible spectral range, and an increased refractive index with increasing bismuth content.     

Refractive index,density and the coordination number of aluminum

Comparison of observed and calculated values of the molar refractivities of calcium aluminates and calcium aluminate hydrates gives information about the coordination numbers of the aluminum atoms.     

Estimation of the effective conjugation length of oligo-p-phenylenes from specific refractive index increments of solutions

Summary An unusually strong molecular weight dependence of the specific refractive index increment which has been reported for solutions of oligomers (M < 10³) of p-2-methyl phenylene is attributed to the exaltation of polarizability of phenylene units. The saturation length is estimated to be l _s≅ 6 phenylene units. Received: 3 November 1997/Revised version: 20 April 1998/Accepted: 22 April 1998     

Refractive index crossover and the phase diagram of an iPP/PEOc blend

The phase diagram of an isotactic polypropylene/poly(ethylene-octene) copolymer (iPP/PEOc) blend system was investigated using phase contrast optical microscopy, laser light scattering and differential scanning calorimetry (DSC). The sample goes through immiscible (opaque) region to transparent region (seemingly miscible) and back to immiscible (opaque) again as temperature increases through 300 °C region. But it turns out that this is not a real one phase region. It is caused by a temperature dependent inversion of refractive indices between the two component polymers, which can be easily misinterpreted as a miscible region between an upper critical solution temperature (UCST) state and a lower critical solution temperature (LCST) state. With a proper interpretation and analysis of this refractive index inversion, the UCST phase diagram of this iPP/PEOc blend system has been obtained.     

Physical properties of fatty acid methyl esters. II. Refractive index and molar refraction

The refractive indices of methyl oleate, linoleate, linolenate, erucate, and the saturated fatty acid methyl esters from acetate to nonadecanoate have been measured at 20C and 40C for the Na_d, H _α , H _β , H _γ lines. The values for the saturated series have been correlated with the Smittenberg relation. Molar refractions have been computed and checked for additivity. The limiting refractive indices obtained from the Smittenberg relation are compared to those obtained from the molar refraction.     

Refractive index changes in polyacrylates bearing alkyl sulfur groups through the sulfur oxidation reaction

Four polyacrylates with sulfur-containing side chains were prepared to examine the changes in refractive index (RI) induced by sulfur oxidation. Linear alkyl sulfides and alicyclic sulfides, such as 1,3-dithiolane and 1,4-dithiane, were introduced to impart large RIs to polyacrylates. Oxidation of the sulfur polymers by O₃ and m-chloroperoxybenzoic acid led to the formation of the corresponding sulfoxide and sulfone polymers, respectively. Sulfur oxidation occurred completely, which was highlighted by the oxidized polymer exhibiting a refractive index comparable to a polymer that was synthesized using a sulfone monomer. The RI of the linear sulfur polymer increased and decreased due to the formation of sulfoxide and sulfone polymers, respectively. The Abbe number of the polymer with a linear sulfide side chain was 33.4, which increased to 48.7 after oxidation.     

Refractive index as an objective method for evaluation of rancidity in edible oils and fats

Common edible oils and fats (refined peanut oil, seasame oil, safflower oil, and butter oil, ghee) were exposed to direct sunlight, fluorescent light and Schaal Test. Data collected on refractive indices (N _D ²⁵ ) show an increase of the order of 0.001±0.0003 at the stage of development of perceptible rancid odor. The pattern of changes in refractive indices and peroxide values of these edible oils, autoxidized at 100±5 C, show that refractive indices indicate more precisely the termination of the induction periods than peroxide values.     

Refractive index profile of polyethylene fiber using interactive multiple‐beam fizeau fringe analysis

A multiple‐beam interference Fizeau fringes technique is used to measure the refractive index profile of drawn polyethylene fiber. The interference fringe shift in the fiber region has been analyzed automatically using an interactive algorithm. The method takes into consideration the refraction of the light beam when crossing the fiber. Plane polarized light vibrating parallel and perpendicular to the fiber axis are used to obtain the refractive index profiles of both cases. These profiles are used to determine some optical parameters such as the birefringence, the optical orientation function, the polarizability per unit volume, and the value Δα/3α_o, which related to the material structure. The reliability of the method is tested considering the results of drawn polyethylene fiber samples using the manual technique. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3099–3106, 2000