Characterization of cationic copolymers by capillary electrophoresis using indirect UV detection and contactless conductivity detection

► Analysis of non-UV absorbing cationic copolymer by capillary electrophoresis. ► Comparison between indirect UV detection and contactless conductivity detection (C 4D). ► Comparison between neutral and double layer cationic coatings. ► Quantification of residual homopolymer and characterization of the distribution in charge density of the copolymer. ► Both indirect UV and C 4D detection modes could be used with better baseline stability and repeatability using indirect UV detection mode. For many industrial applications, the combination of two different monomers in statistical or diblock copolymers enhances the properties of the corresponding polymer. However, during the polymerization reaction, homopolymers might be formed and can influence the properties for the applications. Consequently, the separation and the quantification of the homopolymers contained in copolymer samples are crucial. In addition, the charge density distribution of the statistical copolymer is an important characteristic for the applications. The purpose of this work was to study the characterization of a statistical copolymer of acrylic acid (AA) and diallyldimethyl ammonium chloride (DADMAC) by capillary electrophoresis (CE) in acidic conditions (cationic copolymers). For that purpose, a free solution electrophoretic separation was carried out according to the charge rate (chemical composition) independently of the molar mass. The second objective was to compare contactless conductivity detection and indirect UV absorbance modes for the quantification of DADMAC homopolymers present in copolymer samples. Different coated capillaries based on neutral or positively charged modification were also compared. The comparison of indirect absorbance UV and contactless conductimetric detection demonstrated that both detection modes can be used for a complete CE characterization of non-UV absorbing PAA-DADMAC copolymers.