Analysis of polyethyleneoxide macromonomers by liquid chromatography along the critical adsorption line.

Polyoxyethylene macromonomers are analyzed by one-dimensional liquid chromatography under different conditions, depending on the required information. These samples may contain polyethylene glycol (PEG) and the corresponding di(meth)acrylate besides the desired mono(meth)acrylate. The molar mass distribution (MMD) of the PEG and the monoester can be obtained by liquid adsorption chromatography (LAC) on a reversed-phase column in acetone-water with a gradient from 10% to 20% acetone. The MMD of the diesters can be obtained with isocratic elution by liquid chromatography at critical conditions (LCCC) on a reversed-phase column in 31% acetone, or using size-exclusion conditions for PEG and LAC conditions for the end groups, which is the case in 40-55% acetone. The absolute amount of the series with different functionality can be obtained by LCCC in ternary mobile phases consisting of acetone, methanol, and water along the critical adsorption line. Under such conditions, all series elute as narrow peaks (regardless their MMD), which can easily be integrated and quantified.