COMPOSITIONAL FRACTIONATION OF COPOLY(STYRENE METHYL-METHACRYLATE) BY NORMAL-PHASE AND REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

It was studied whether both modes of normal-phase (NP) and reversed-phase (RP) of adsorption chromatography can work effectively for the compositional fractionation of copolymer by high-performance liquid chromatography (HPLC) under the coexistence of both mechanisms of adsorption and phase-separation. The fractionation of a mixture of 4 copoly(styrene/methyl methacrylate) samples with different chemical compositions by gradient HPLC was tried for 8 cases using combinations of 2 eluents of tetrahydrofuran(THF)/cyclohexane(CHX) and THF/acetonytrile(ACN), and 4 columns of modified silica gel with NH2-, CN-, Phenyl- and octadecyl(ODS)-groups. The mixture was fractionated effectively according to chemical composition by 4 combinations of THF/CHX and high-polar columns (NH2, CN), and THF/ACN and non-polar columns (Phenyl, ODS), which are the fitting combinations for the scheme of NP or RP adsorption. However, other combinations, could not give the effective separation. For the gradient HPLC by the fitting combinations, THF-contents of the eluents at peak positions were higher than those at the first cloud points for the respective copolymer samples, and also the molecular weight dependence of the peak position was negligible. It may thus be concluded that adsorption mechanism is predominant than phase-separation mechanism in the system of the fitting combination of eluents and columns for the scheme of NP or RP mode. © 1990, The Society of Polymer Science, Japan. All rights reserved.