SynopsisIsotactic polystyrene fractions were characterized by gel permeation chromatography (GPC) in tetrahydrofuran (THF) a t 25OC. From the universal calibration method, a viscosity law has been established allowing determination of the correspondence between the molecular weight GPC calibration laws for APS and IPS. The validity of characterization of IPS by this method was confirmed with light scattering and osmometry.
SynopsisIn this paper, a new method for correcting GPC results in order to take into account the axial dispersion of a given set of columns is proposed. The idea is to evaluate the different average molecular weights and the polydispersity for a given elution volume. In order to do so, one needs only to know the efficiency of the set of columns and the different derivatives at a given point of the chromatogram. Some possible applications of this method are reviewed mainly for the characterization of polydispersity and for the determination of the viscosity law if one uses the universal calibration.
Chromatographic columns were filled with anionically prepared polystyrene gels of various porosities. Linear polystyrene samples were injected in these columns and the retention volumes were measured. Normalized curves have been compared, the dynamic partition coefficient being plotted wersus the logarithm of the molecular weight of the injected polymer. It has been established that the domain of molecular weights in which chromatographic separation may take place depends upon the parameters characterizing the gel: molecular weight of the linear "precursor", overall concentration at the gel point, proportion of crosslinking agent.It has been found that the chromatographic retention times depend on such factors as size of gel particles, flow-rate of the elution solvent. This shows that the exchange equilibrium between the pores of the gels and the flowing intersticial liquid are far from being fulfilled. However by choosing standard conditions one gets reproducible results which may be adequately compared.It should be emphasized that macroporosity of a gel is not a prerequisit for chromatographic separation.
ZUSAMMENFASSUNG:Chromatographische Kolonnen wurden mit anionisch hergestellten Polystyrolgelen verschiedener PorengroSen gefiillt. Lineare Polystyrolproben wurden in diese Kolonnen eingespritzt, und die entsprechenden Elutionsvolumina wurden gemessen. Durch die normalisierten Elutionskurven -die die dynamischen Verteilungskoeffizienten in Abhangigkeit des Logarithmus des Molekulargewichtes des eingespritzten Polystyrols darstellen -wurde veranschaulicht, daS der Molekulargewichtsbereich, in dem chromatographische Trennung stattfinden kann, von den strukturellen Parametern des Gels abhangig ist, und zwar von dem Molekulargewicht des linearen Prapolymeren, von der Konzentration des Polymeren beim Vernetzungsvorgang und vom Anteil des Vernetzungsagens.Es wurde auch festgestellt, daS die chromatographischen Elutionsvolumina von Faktoren abhangig sind, wie der GroSe der Gelpartikel und der Fliefigeschwindigkeit des Eluenten. Dies zeigt, daS die Bediugungen zur Einstellung des Austauschgleichgewichtes zwischen den Gelporen und der flieaenden Zwischenraumfliissigkeit nicht erfiillt sein konnen. Aber unter Verwenduug von Standardbedingungen kann man reproduzierbare Ergebnisse erzielen, die zp g$tigen .Vergleichen dienen kiinneu.Es ist noch hervorzuheben, dal3 die Makroporositat eines Gels keineswegs als eine notwendige Bedingung fur die chromatographische Trennung aufzufassen ist. 105 P. WEISS, J. HERZ, P. REMPP, 2. GALLOT et H. BENO~T
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