6533b825fe1ef96bd128309b

RESEARCH PRODUCT

Syntheses and properties of gel chromatography materials

subject

description

Abstract The effect of the mode of synthesis on the characteristics of cross-linked polymers is examined for cross-linked copolymers of ethylvinylbenzene-divinylbenzene and vinyl acetate-divinyl adipate. For homogenously cross-linked gels the amount of cross-linking agent determines the “pore size” of these gels in the swollen state. Decreasing the amount of the divinyl component results in gels with an increase in the excluded molecular weight. The mechanical stability sets the experimental limit of their usage, so this type of gel is mostly suited for the separation of oligomers; polymers, however, may be separated by use of heterogenously cross-linked gels. The latter type of gel is prepared by using high amounts of cross-linking agent and polymerising in the presence of an inert compound. It is demonstrated that in case of a heterogeneously cross-linking polymerisation the heterogeneity of the copolymers increases while at the same time the solvating ability of the inert component decreases; this leads simultaneously to an increase in the excluded molecular weight. A decrease in the quality of the solvent using a non-polar non-solvent may result in gels having a dense shell. Gels with such balloon-like structures separate over a narrow range of molecular weights. As to be expected by theory, substances which are totally excluded ( V e = V o and substances which can easily penetrate these gels give sharp peaks, whereas substances in the separation range give broad peaks.