Polymers chromatography

Also, there might be absorptions in the IR spectra which are characteristic for syn- or isotacticity (such as in PMMA) or for branching points of nonlinear polymer chains (such as in polyethylene). Using data pools and programs which simulate IR spectra it is possible nowadays to characterize nearly all kinds of polymers very quickly using IR spectroscopy with respect to their constitution and their composition. Also, IR spectroscopy can be coupled with polymer chromatography (SEC, HPLC). Then it provides detailed chemical information on each individual chromatographic fraction. 

Another requirement is the accessibility of the active surface. A pore size of 30 or 50 nm is adequate in most cases of interactive polymer chromatography. The pore diameter must not be too large because the internal surface of the packing decreases with increasing pore diameter. 

A column (250 x 4.6 mm) packed with a reversed-phase C 18 support, coated with trioctylmethyl ammoniumchloride, separated oligo-uridylic acids and discriminated between (Up)89 and (Up)q0, (Fig. 23)83). In such high a region of molar mass, the separation of components differing in only one monomeric unit is remarkable in polymer chromatography in general. 

Keywords Molecular recognition Imprinting Polymer Chromatography Catalysis... 

A recent audit (by the authors) of a number of videos of chemistry presentations given to diverse live audiences in Australia, the UK and the USA showed that most of them are of hour-long shows. They range over a wide variety of topics which include acids and bases, redox reactions, polymers, chromatography, spectra, and so on. The theme in each case appeared to be a focus on astonishing visual or sound effects, rather than on... 

In our study the butanol-soluble fraction was proved to be effective for terminating pregnancy in rats. The results agreed with literature reports and suggested the active principles should be hydrophilic components. However, some soponins we subjected to test showed not effective and the water eluent on a highly porous polymer chromatography seems much better than individual saponin in animal test. The experiments should be repeated and confirmed to make a conclusion carefully. 

The molecular-statistical theory of polymer solutions in confined media was also applied to the conventional chromatographic theory of gradient elution [ 163]. This approach leads to the prediction of the special mode of interactive polymer chromatography gradient elution at critical point of adsorption. It was demonstrated theoretically and experimentally that under appropriate conditions elution of each compositionally homogeneous fraction of copolymer occurs at the critical mobile phase composition. This critical mobile phase composition depends only on the local structure of the copolymer chain and is independent of its molecular weight. As a consequence, gradient elution produces the chemical com-... 

Pores (mean diameter usually from 6 to 100 nm) play a cmcial role in hplc, as they provide the surface where retention and hence separation occur. The chemical stmcture of the surface determines the thermodynamic environment for the analyte in thin surface layer (stationary phase) and in such a way determines the mechanism of retention. Flexible macromolecules approaching the internal surface of a solid particle change their spatial conformations because of steric interaction, which plays an important role in any mode of polymer chromatography. This interaction restricts the fluctuation motion of a macromolecule, decreases its... 

Refs. 1, 8, and 17 deal with theoretical aspects of polymer chromatography. 

Isocratic polymer chromatography at adsorbing conditions can be applied only to oligomers, as high molar-mass pol)nners even of narrow molar-mass distribution are partially adsorbed for infinite times on the column. Hence, interaction chromatography of pol)nners usually is performed using solvent gradients. 

Brun Y. The mechanism of copolymer retention in interactive polymer chromatography, II. Gradient separation. J Liq Chrom Rel Technol 1999 22 3067. 

Brun Y, Foster P. Characterization of synthetic copolymers by interaction polymer chromatography separation by microstructure. J Sep Sd 2010 33 3501—10. 

Although excluded-volume effects are well-accepted in polymer chromatography, the preceding arguments are not without controversy in the petroleum literature because of the way that the apparent polymer viscosity in porous media was determined. In our work, we simply report the resistance factor (i.e., the brine mobility before polymer injection divided by the polymer-solution mobility). This is a well-defined parameter that derives directly from the Darcy equation and measurements of pressure drops and flow rates. Advocates of the depletion-layer effects use a different method to determine apparent polymer viscosity in porous media. Specifically, they flush water through the core after polymer injection to determine the permeability reduction or residual resistance factor. The resistance factor during polymer injection is then divided by the residual resistance factor to determine the apparent polymer viscosity in porous media. Unfortunately, several experimental factors can lead to incorrect measurement of high residual resistance factors, which, in turn, lead to calculation of unexpectedly low apparent polymer viscosities in porous media. 

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