Separation of poly(acrylic acid) salts according to topology using capillary electrophoresis in the critical conditions

International audienceBranching was detected in polyacrylates synthesised through radical polymerization via solution-state NMR, while inconsistencies had been reported for the determination of the molar mass of hydrophilic polyacrylates between aqueous-phase and organic-phase size-exclusion chromatography (SEC). In this work, poly(sodium acrylate)s, PNaAs, of various topologies were separated for the first time using free-solution capillary electrophoresis. Free-solution CE does not separate the PNaAs by their molar mass, similarly to separations by liquid chromatography in the critical conditions. PNaAs with different topologies (linear, star branched and hyperbranched) were separated using free-solution CE. The electrophoretic mobility of PNaAs increases as the degree of branching decreases. Separation is shown to be not only by the topology but also by the end groups as expected for a separation in the critical conditions: replacing a relatively bulky nitroxide end group with hydrogen atom yielded a higher electrophoretic mobility. This novel method, capillary electrophoresis in the critical conditions enabled, for the first time, the characterization of hydrophilic polyacrylates according to their topology (branching) and their chain ends. This will enable meaningful and accurate characterization of their branched topologies as well as molar masses and enable advances for advanced applications such as drug delivery or flocculation