Liquid chromatography of polymer mixtures applying a combination of exclusion and full adsorption mechanisms. 5. Six-component blends of chemically similar polymers

The separation of six-component blends of chemically similar homopolymers u tilising the full adsorption-desorption (FAD) process is presented. The mai n advantage of the FAD approach over other methods represents the successiv e and independent size-exclusion chromatography (SEC) characterisation of a ll blend components. The method is based on the full adsorption and retenti on of all n or n-1 components of the polymer blend from an adsorption promo ting liquid (ADSORLI) in a small FAD column. Nonadsorbed macromolecules are forwarded directly into SEC for molecular characterisation. Next, appropri ate displacers are successively applied to the FAD column to selectively re lease-preadsorbed blend constituents into the on-line SEC column. Dynamic i ntegral desorption isotherms for single constituents, as well as for polyme r blends to be analysed, allow identification of optimal displacer composit ions to release just one kind of macromolecule. Model polymer blends contai ning polystyrene (PS), poly(lauryl methacrylate), poly(butyl methacrylate), poly(ethyl methacrylate), poly(methyl methacrylate) and poly(ethylene oxid e) (PEO) or, alternatively, PS, poly(2-ethylhexyl acrylate), poly(butyl acr ylate), poly(ethyl acrylate), poly(methyl acrylate) and PEO of similar mola r masses can be separated and characterised in one multistep run using nonp orous silica FAD packing, toluene as an ADSORLI and its mixtures with a des orption promoting liquid such as ethyl acetate, tetrahydrofuran or dimetylf ormamide to form displacers with appropriate desorption strength.