MOLDED MONOLITHIC ROD OF MACROPOROUS POLY(STYRENE-CO-DIVINYLBENZENE) AS A SEPARATION MEDIUM FOR HPLC OF SYNTHETIC-POLYMERS - ON-COLUMN PRECIPITATION-REDISSOLUTION CHROMATOGRAPHY AS AN ALTERNATIVE TO SIZE-EXCLUSION CHROMATOGRAPHY OF STYRENE OLIGOMERS AND POLYMERS

A process fort the separation of styrene oligomers and polymers by siz e and composition using a novel separation medium has been demonstrate d, The process involves precipitation of the macromolecules on the mol ded macroporous rod columns, followed by progressive elution utilizing a simple gradient of the mobile phase, Molded macroporous rod columns are ideally suited for this technique because convection through the large pores of the rod enhances the mass transport of large analyte mo lecules and accelerates the separation process, Styrene oligomers and polymers are separated in a 50-mm x 8-mm-i.d. column using a solvent g radient composed of a poor solvent such as water, methanol, or acetoni trile and increasing amounts of a good solvent, tetrahydrofuran, Excel lent separations are obtained, demonstrating that precipitation-rediss olution can be a suitable alternate to size exclusion chromatography ( SEC) of some polymers, Compared to SEC, the gradient elution separatio n can be achieved at higher now rates in a much shorter time, Precipit ation-redissolution with gradient elution can also be used for the sep aration of copolymers, for which the process is controlled not only by molecular weight but also by the composition of the copolymers.