Separation of block copolymers from parent homopolymers by means of liquid chromatography at the critical adsorption point

The characterization of a block copolymer consisting of blocks of tetrahydrofuran, THF, and methyl methacrylate, MMA, was attempted with the aid of liquid chromatography, LC, at the critical adsorption point, CAP. The conditions applying to the CAP at 30 degrees C for the homopolymers are: PTHF: eluent composition: THF:acetonitrile = 50:50, w/w; column: Nucleosil C-18. PMMA: eluent composition: THF:n-hexane = 81.8:18.2, w/w; column: bare silica gel. The presence of homo PTHF and of homo PMMA in the crude block copolymer was evidenced. Moreover, chromatography at the CAP for PMMA showed that the block copolymer contains multiblock (triblock) fractions. The formation of triblock copolymer is expected when the polymerization of MMA is terminated (partially) by combination. In conclusion, LC at the CAP is a powerful tool to characterize block copolymers regarding the presence of homopolymer and multiblock (triblock) fractions.