Size-exclusion chromatography polymer characterization using

Cotton fibers are single cells composed primarily ( 96%) of the polymer cellulose. In our laboratory (5), cotton fibers were dissolved directly in the solvent DMAC-LiCl. This procedure solubilizes fiber cell wall components directly without prior extraction or derivatization, processes that could lead to degradation of high MW components. MW determinations have been carried out by a size-exclusion chromatography (SEC) system using commercial columns and instrumentation with DMAC-LiCl as the mobile phase. Incorporation of viscometry and refractive index (RI) detectors (6) allowed application of the universal calibration concept (7) to obtain MW distributions (MWDs) based on well-characterized narrow-distribution polystyrene standards (5). The universal calibration concept used by incorporation of dual detectors bypasses the need for cellulose standards. There are no cellulose standards available. Polystyrene standards for a wide range of MWs dissolved readily in DMAC-0.5% LiCl with no activation necessary. 

Size exclusion chromatography can be used to separate polymer molecules according to their size in solution, and size can be converted to molecular weight by calibration. SEC cannot be used to separate polymers according to chemical composition or functionality. For this purpose, interactive liquid chromatography (i-LC) may be used. In i-LC the molecules of the analyte polymers interact with the mobile phase and with the stationary phase in the column. Usually, thermodynamic equilibrium is reached at any point in the column. The distribution of the polymer molecules across the two phases can then be characterized by a distribution coefficient (K = Cs/Cm, where Cg is the concentration of the polymer in the stationary... 

High-performance size exclusion chromatography is used for the characterization of copolymers, as well as for biopolymers (3). The packings for analyses of water-soluble polymers mainly consist of 5- to 10-/Am particles derived from deactivated silica or hydrophilic polymeric supports. For the investigation of organosoluble polymers, cross-linked polystyrene beads are still the column packing of choice. 

Meehan, E. and O Donohue, S., Characterization of block copolymers using size exclusion chromatography with multiple detectors, in Chromatographic Characterization of Polymers, Hyphenated and Multidimensional Techniques, Provder, T., Barth, H. G., and Urban, M. W., Eds., American Chemical Society, Washington, D.C., 1995, chap. 18. 

A combination of infrared spectroscopy with size exclusion chromatography has a wide application range in the characterization of copolymers, adhesives, impurity profiling in polymers and branching in polyolefines [60-65]. Commonly, the solvent used as a mobile phase absorbs strongly in the... 

Size exclusion chromatography (SEC) polymer elution profiles yield information regarding the molecular size distributions of polydisperse macromolecules. Polymer molecular weight distribution (MWD) represents an intrinsic property which provides direct correlation with many end-use physical properties and a universal criterion for polymer characterization (1). In order to convert elution profiles or chromatograms into MWD information proper calibration methods are required. SEC molecular weight calibration techniques represent experimental approaches for transformation of polymer elution profiles into MWD information and are dependent upon instrumentation, columns, and the polymer/solvent system under study. 

The architecture of hypeibranched polymers and dendrimers is connected with difficulties in determining molar mass. Many of the common characterization techniques—e.g. size exclusion chromatography (SEC)—used for polymers are relative methods where polymer standards of known molar mass and dispersity are needed for calibration. Highly branched polymers exhibit a different relationship between molar mass and hydrodynamic radius than their linear counterparts. 

Another chromatographic method, which is related to HPLC, is Size Exclusion Chromatography.16 In this technique, separation is based on molecular size. The analytes do not interact with the column material, but are separated on basis of the amount of pores into which they may penetrate. SEC is used for the separation and characterization of synthetic and natural water-soluble polymers. Organic or silica-... 

Barth, H. G., (1986). Characterization of water-soluble polymers using size-exclusion chromatography. In Water-Soluble Polymers, Glass, J. E., Jr. (Ed.). Advances in Chemistry, 213, pp. 31-55. Am. Chem. Soc., Washington, DC. 

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