Dynamic behavior and fractional analysis of dilute rigid polymer solutions using packed hydrodynamic chromatography

Abstract

Recently, hydrodynamic chromatography (HDC) has become an important probe for determining the molecular size or molecular shape in the sub-micron range. Porous media flow within packed HDC column has attracted important attention because in which confined geometries have a great influence on dynamics of polymer molecules; e.g., flow-induced conformation of polymer chains. Although considerable work has been devoted to HDC analysis, the clear understanding on the transport behavior of polymer solutions in porous media has not been achieved yet. In this present study, the flow and dynamic behavior of rigid rodlike polymer molecules in a packed HDC column is fully analyzed by extending the molecular theory of dilute polymer solution in a confined geometry in order to elucidate quantitatively the effects of arbitrary particle sizes as well as of flow strength on the dimensionless separation parameter, namely, retention factor ($R_f$). $R_f$ equations of each simple polymer model, i.e. isotropic single Brownian(SB) and rigid dumbbell (RD), were developed, and then numerical simulations were clearly worked out to illustrate the $R_f$ for rigid rod (RR) poymer. Remarkably, theoretical predictions were in close agreement with the present experimental results of RR polymer via xanthan gum, that is water-soluble high molecular weight biopolymer, and other previously published data of SB model particles despite of several approximations. The $R_f$ value showed the gradual increasing behavior as particle size (i.e., ∈ parameter) increased, however, for RR model the $R_f$ decreased with increasing the flow strength within a particular range of about 0 ＜ log β ＜ 3. Additionally, in the outside of this region the significant flow-independent $R_f$ behavior could be observed. This feature emphasized a transition behavior from weak to strong flow due to the flow-induced orientational effect of xanthan molecules. In order to analyze the fractionation of xanthan polymer cal...