Analysis of charged acrylic particles by on-line comprehensive two-dimensional liquid chromatography and automated data-processing

A thorough understanding of particle formation and polymer growth during emulsion polymerization is indispensable for the development of particles and products with very specific properties. This has created a demand for the detailed characterization of various properties and property distributions - and the relation between these. A method is described that enables comprehensive, simultaneous determination of the size distribution of nanoparticles and the molecular-weight distribution of the constituting polymers as a function of the particle size. The result is a complete two-dimensional distribution that details the interdependence of the two parameters. The approach comprehensively combines hydrodynamic chromatography with size-exclusion chromatography. An automated band-roadening filter has been developed to improve the accuracy of the measured distributions. The algorithm utilizes automated curve-fitting approaches to describe detected particle distributions for each horizontal slice of the 2D-LC chromatogram, and filters band broadening using calibration curves. The method has been applied to samples of complex nanoparticles comprising hydrophobic, hydrophilic and charged moieties, viz. stabilized dispersions of poly[(methyl methacrylate)-co-(butyl acrylate)-co-(methacrylic acid)]-nanoparticles in water. We consistently found that, within a single population of particles, the weight-average molecular weight increases with particle size.