Liquid chromatography of polymer mixtures by a combination of exclusion and full adsorption mechanisms. Three- and four-component polymer blends

Abstract

SummaryCoupling of full adsorption-desorption and sizeexclusion chromatography (FAD-SEC) has been applied to the separation and molecular characterization of three-and four-component polymer blends. The method is based on the full adsorption of all n or n -1 components of the polymer blend in a specially designed FAD minicolumn. By appropriate eluent switching the adsorbed polymer s are desorbed stepwise from the FAD minicolumn into an on-line SEC column for molecular characterization. It is shown that the desorption isotherms of particular blend components give valuable information about the appropriate displacer composition. The exact position of the desorption isotherms depends, however, both on the amount of polymer adsorbed and in the presence of other, chemically different, polymers within FAD column. The nature and composition of the displacer must, therefore, be adjusted if the intervals between the desorption of particular blend components are to be large enough to prevent displacement overlap.

Molecular characterization of statistical copolymers: 1. Potential and limitations of full adsorption-desorption procedure in separation of statistical copolymers

“…The recently developed method called full adsorption–desorption (FAD)10–14 can mitigate at least some of above problems. As the name indicates, FAD is based on the temporary immobilization of the complex polymer sample within a specially designed (micro)column from which macromolecules are successively released in a controlled way by means of a series of desorbing liquids with increasing displacement strength.…”

Reconcentration of diluted polymer solutions by full adsorption/desorption procedure: II. Desorption of macromolecules by a narrow pulse of displacer

“…The alternative explanation of the course of the dynamic desorption curve for PVAc when compared with PTHF and PMMA of the same range of molar masses considers stronger adsorption of PVAc from toluene on the bare silica surface so that the order of adsorption affinities is PTHF ϳ PMMA Ͻ PVAc. 7,8 The shape of the dynamic desorption curve indicates suitability of a particular system adsorbent-ADSORLI-DESORLI for reconcentration of a given polymer: The systems with a low volume of DESORLI to start displacement and with steep dynamic desorption curves are preferred.…”

Molecular characterization of statistical copolymers: 1. Potential and limitations of full adsorption–desorption procedure in separation of statistical copolymers

“…The FAD column sample capacity was not very important for separation of two-and even multicomponent polymer blends with a nearly equal relative concentration of constituents. 12 On the other hand, the limited FAD column sample capacity could represent an important problem in the case of copolymer fractionation where an increased number of fractions must be produced. The course of polymer desorption can be easily assessed applying a pilot FAD approach to simultaneously evaluate and optimize the experimental system.…”

“…The course of polymer desorption can be easily assessed applying a pilot FAD approach to simultaneously evaluate and optimize the experimental system. For this purpose, we have monitored the dynamic integral desorption isotherms [12][13][14][15][16][17] of model PMMAs and copolymers. Samples with different MMMs, medium broad MMDs, and rather narrow CCDs were selected.…”