Macromolecules, Vol.33, No.5, 1710-1715, 2000
Discrimination of poly(ethyl methacrylate)s according to their molar mass and tacticity by coupling size exclusion chromatography and liquid chromatography at the critical adsorption point
A coupling of size exclusion chromatography (SEC) and liquid chromatography at the critical adsorption point (LC CAP) has been applied to simultaneous discrimination of stereoregular poly(ethyl methacrylate)s (PEMAs) according to their molar mass and tacticity. The two-dimensional SEC/LC CAP separations were carried out with a chromatographic system which consisted of two analytical columns, one SEC column (polystyrene/divinylbenzene gel) and one LC CAP column(aminopropyl bonded silica gel) connected in series. Narrow fractions of PEMA samples eluted from the SEC column were on-line forwarded into the LC CAP column to be separated according to their tacticity. The column system was flushed with tetrahydrofuran (THF)/cyclohexane mixed eluents at compositions of 64/36 and 56/44 w/w, to attain the molar-mass-independent elution of either highly syndiotactic or highly isotactic PEMAs, respectively. In these eluents, the SEC column still separated PEMAs solely according to their molar masses, while the LC CAP column system discriminated PEMAs according to their tacticity. By use of the coupled SEC/LC CAP technique, the influence of molar mass distribution of analyzed sample on its separation according to tacticity in the LC CAP column was suppressed. For the first time the separation of stereoregular polymers over the entire tacticity range has been demonstrated.
Keywords:MOLECULAR-WEIGHT DISTRIBUTION;POLY(METHYL METHACRYLATE);SEPARATION;DEPENDENCE;TOLUENE;PMMAS