Analytical Technology Centre, DSM Coating Resins, Sluisweg 12, 5145PE Waalwijk, The Netherlands.
Van't Hoff Institute for Molecular Science (HIMS), University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands.
Anal Chem. 2021 Apr 13;93(14):5924-5930. doi: 10.1021/acs.analchem.1c00311. Epub 2021 Apr 1.
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, -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.
由于与传统溶剂型聚合物体系相比具有良好的生态特性，水基聚合物的需求正在不断增加。许多水基聚合物颗粒在水性介质中通过加入酸官能单体来稳定。由于应用的共聚单体种类繁多，这些水基聚合物具有各种叠加的统计分布，这使得很难获得有关酸性单体掺入的深入信息。为了选择性地分析掺入的酸性单体，开发了基于电荷的非水毛细管电泳（NACE）分离。开发了两种方法：（i）用可溶的有机强碱使酸官能团去质子化，（ii）羧酸的阴离子与掺入的酸官能团进行杂共轭。在这两种方法中，均使用 N-甲基吡咯烷酮作为具有有利于离解离子物种存在的相对介电常数的聚合物的强溶剂。结果表明，羧酸的阴离子与聚合物中的掺入的酸基团特异性缔合，形成带负电荷的复合物，可通过 NACE 基于电荷-大小比进行分离。尽管这两种方法在酸官能聚合物的酸分布方面都能得到可比的结果，但去质子化聚合物的有效迁移率大约是杂共轭方法的两倍。与杂共轭方法不同，去质子化条件对熔融石英毛细管有害，限制了实际应用。对具有不同化学组成、分子量和酸含量的聚合物进行了 CE 方法的研究。具有不同分子量但相对酸单体含量相似的聚合物显示出相似的迁移时间，这证实了该方法根据电荷-大小比分离聚合物。
