Simulation formulae are derived for determining polymer structure in an infinitesimal fraction of GPC elution volume.
If sample is ideally fractionated, molecular weight distribution (MWD) of the momentary eluted polymer depends chiefly on distribution of number of branching points per molecule (DNBP) of injected sample. Statistically branched polymer indicates almost monodisperse MWD. Separation is sharper in high molecular weight region than in low region. Even if DNBP is broader, the average number of branching points can be correctly estimated by the method proposed by Kurata et al., as far as the DNBP is nearly Gaussian.
When sample is fractionated by a real GPC with axial dispersion, MWD of the eluted polymer is mainly controlled by instrumental spreading function, unless sample has extremely wide DNBP or special MWD. The average number of braching points by the Kurata equation is expected more reliable, if a polydisperse linear polymer that yields chromatogram similar to the branched sample is applied as reference.
View full abstract