LIQUID-CHROMATOGRAPHY OF POLYMER MIXTURES APPLYING A COMBINATION OF EXCLUSION AND FULL ADSORPTION MECHANISMS .2. ELUENT SWITCHING APPROACH

The molar mass and molar mass distribution of particular components of a polymer mixture can be determined by a combination of size exclusion chromatography (s.e.c.) and full adsorption/desorption (f.a.d.) modes. One component of a polymer mixture is retained on the surface of an appropriate sorbent using an appropriate eluent while another component is chromatographed in the conventional s.e.c. mode. In the next step the eluent is changed so that the previously retained polymer is desorbed and analysed in the s.e.c. mode. This idea is demonstrated with a mixture of polystyrene (PS) and poly(methyl methacrylate) (PMMA) using two different f.a.d. columns packed with a silica-based sorbent and a s.e.c. column packed with polystyrene gel. Using toluene as eluent, PMMA was retained on the f.a.d. silica gel packed column while PS was eluted in the typical s.e.c. mode and the molar mass and molar mass distribution of PS could be determined in the first step. After switching the eluent from toluene to tetrahydrofuran in the second step, PMMA was desorbed from the f.a.d. column and swept into the s.e.c. column where its molar mass and molar mass distribution could be determined as well.