Charge-Based Separation of Acid-Functional Polymers by Non-aqueous Capillary Electrophoresis Employing Deprotonation and Heteroconjugation Approaches

Abstract

Water-borne polymers are in ever-increasing demand due to their favorable ecological profile compared to traditional solvent-borne polymer systems. Many water-borne polymer particles are stabilized in aqueous media by the incorporation of acid-functional monomers. Due to the large variety of comonomers applied, these water-borne polymers have various superimposed statistical distributions, which make it challenging to obtain in-depth information regarding incorporation of the acidic monomers. For selective analysis of the incorporated acidic monomers, a charge-based non-aqueous capillary electrophoresis (NACE) separation was developed. Two approaches were developed: (i) deprotonation of the acid functionality with an organically soluble strong base and (ii) heteroconjugation of anions of carboxylic acids with incorporated acid functionality. In both approaches, N-methylpyrrolidone, as a strong solvent for polymers with a favorable relative permittivity for the presence of dissociated ionic species, was used for the separation. It was shown that anions of carboxylic acids specifically associate with the incorporated acid groups in the polymers, resulting in negatively charged complexes that could be separated based on charge-to-size ratio by NACE. Although both approaches give comparable results with respect to acid distribution for acid-functional polymers, the effective mobility of the deprotonated polymers is roughly double that obtained from the heteroconjugation approach. Unlike the heteroconjugation approach, deprotonation conditions were detrimental to the fused-silica capillary, limiting practical use. Polymers with different chemical compositions, molecular weights, and acid contents were subjected to the CE approaches developed. Polymers with varying molecular weight but similar relative acid monomer content were shown to have similar migration times, which confirms that this approach separates polymers based on charge-to-size ratio.

Preparation of graphene oxide–stabilized Pickering emulsion adjuvant for Pgp3 recombinant vaccine and enhanced immunoprotection against Chlamydia Trachomatis infection

“…In addition, particle concentration and water/oil ratio had a remarkable influence on the emulsion stability and droplet size because increased GO concentration on the oil−water interface reduced the free energy, made the system more stable, and reduced the droplet size, findings which have been confirmed by nearly all related research ( 30 ). A high water/oil ratio resulted in a higher GO concentration, which also reduced the droplet size because the ability of GO to act as a surfactant was strongly favored by squalene, a non-polar and aromatic oil phase ( 31 , 32 ). Finally, for salinity and pH, some similar research also supported our result that changes in salinity and pH might alter GO’s amphiphilic properties ( 33 ), because base-enhanced deprotonation of carboxylic acid groups on the nanosheet edges improved their dispersibility, further affecting droplet stability and size ( 34 , 35 ).…”

Capillary Electrophoresis: A Three-Year Literature Review

“…A charge-based nonaqueous capillary electrophoresis (NACE) method, utilizing N -methyl-2-pyrrolidone as the solvent, was used to determine the acid functionality distribution in various methacrylic model systems. This method proves valuable for the specific characterization of polymers based on their incorporation of acidic monomers …”

“…This method proves valuable for the specific characterization of polymers based on their incorporation of acidic monomers. 89 In recent years, organic solvents have also received considerable attention for their compatibility with detectors coupled to CE, especially in downstream MS-based analyses. 90 They are known to provide better separation performance and solubility of hydrophobic ionic compounds compared to aqueous buffers.…”

Recycling gradient-elution liquid chromatography for the analysis of chemical-composition distributions of polymers

“…However, in certain cases it can be desirable to have a one-dimensional method available that can provide information on solely the CCD, as this avoids the practical complexity of 2D-LC. Currently there are no easy-to-implement methods that do so, although examples of such separations exist [18][19][20] . One approach which may potentially be applied for this is recycling liquid chromatography (LC LC).…”