Aggregation Behavior of Asymmetric Diblock Polyampholyte in Aqueous Solution over a Wide Range of pH and Ionic Strength,Macromolecular Chemistry and Physics

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Aggregation Behavior of Asymmetric Diblock Polyampholyte in Aqueous Solution over a Wide Range of pH and Ionic Strength
Macromolecular Chemistry and Physics ( IF 2.5 ) Pub Date : 2021-09-12 , DOI: 10.1002/macp.202100141
Suelen G. Trindade ₁ , Nádya P. da Silveira ₂ , Watson Loh ₁

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The aggregation behavior of the asymmetric diblock polyampholyte poly(2-(dimethylamino)ethyl methacrylate-block-poly(acrylic acid) (PDMAEMA₈₆-b-PAA₂₄) is studied by static and dynamic light scattering techniques (S/DLS) in aqueous solutions. The molecular assemblies formed by this copolymer are monitored in pure water and over a wide pH range. At pH 5.5, where both blocks are ionized, spherical polymer micelles with hydrodynamic radius (R_H) around 124 nm are detected. These micelles are composed of a large and highly hydrated core formed by the electrostatic complexation between the oppositely charged blocks, and a corona formed by the uncompensated cationic PDMAEMA chains. By combining the results of light scattering, small angle X-ray scattering (SAXS), and cryogenic transmission eletron microscopy (Cryo-TEM) techniques and the predictions of theoretical models from the literature, an aggregation model is proposed, similar to already described crew-cut micelles. These aggregates display resistance to high ionic strengths, suggesting a transition from electrostatic to hydrophobic intermolecular interactions accounting for micelle formation, which is confirmed by the increased incorporation of a hydrophobic probe. The persistence of the aggregates even in conditions at which one of the blocks displays no charge (at extreme pH values) or with high salt concentration, is attributed to remaining hydrogen bonding or hydrophobic interactions that contribute to the core formation.

中文翻译：

不对称二嵌段聚两性电解质在较宽的 pH 值和离子强度范围内在水溶液中的聚集行为

通过静态和动态光散射技术 (S/DLS) 在水溶液中研究了不对称二嵌段聚两性电解质聚（2-（二甲氨基）乙基甲基丙烯酸酯-嵌段-聚（丙烯酸）（PDMAEMA ₈₆ - b -PAA ₂₄）的聚集行为。溶液。由该共聚物形成的分子组装在纯水中和在很宽的 pH 范围内进行监测。在 pH 5.5 时，两个嵌段都被电离，具有流体动力学半径的球形聚合物胶束 ( R _H) 大约 124 nm 被检测到。这些胶束由带相反电荷的嵌段之间的静电络合形成的大且高度水合的核和由未补偿的阳离子 PDMAEMA 链形成的电晕组成。通过结合光散射、小角 X 射线散射 (SAXS) 和低温透射电子显微镜 (Cryo-TEM) 技术的结果以及文献中理论模型的预测，提出了一个聚合模型，类似于已经描述的机组人员-切割胶束。这些聚集体显示出对高离子强度的抵抗力，表明从静电到疏水性分子间相互作用的转变解释了胶束的形成，这通过增加疏水性探针的掺入得到证实。

更新日期：2021-10-07

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