Self-Assembly of Charge-Containing Copolymers at the Liquid-Liquid Interface
Self-Assembly of Charge-Containing Copolymers at the Liquid-Liquid Interface
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DOI：
10.1021/acscentsci.9b00084
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发表时间：
2019-04-24
影响因子：
18.2
通讯作者：
de la Cruz, Monica Olvera
中科院分区：
文献类型：
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作者：
Jimenez-Angeles, Felipe;Kwon, Ha-Kyung;de la Cruz, Monica Olvera
定量地理解两亲性大分子在液-液界面处的自组装是一个基本的科学问题，因为它与广泛的应用相关，包括自下而上的纳米图案化、蛋白质封装、石油回收、药物递送和其他技术。由于疏水性、亲水性和库仑相互作用的组合，阐明驱动两亲性大分子在液-液界面组装的机制是具有挑战性的，这需要考虑介电失配、溶剂化效应、离子相关性和熵因子。在这里，我们调查的自组装模型嵌段共聚物在氯仿-水界面的各种电荷分数。我们分析了吸附和构象的聚（苯乙烯）-嵌段-聚（2-乙烯基吡啶）（PS-b-P2 VP）和具有不同电荷分数的均聚物聚（2-乙烯基吡啶）（P2 VP），这是通过季铵化反应控制和随机分布沿着骨干。界面张力测量表明，聚合物吸附仅在低电荷分数（< 5%）时略有增加，但在共聚物的较高电荷分数时增加得更显著，而相应的无规电荷P2 VP均聚物类似物对带电基团的存在表现出更大的敏感性。分子动力学（MD）模拟结果表明，嵌段共聚物（PS-b-P2 VP）的界面活性是通过形成一系列复杂的界面聚合物聚集体来介导的。随着电荷分数的增加，在水-氯仿界面处的模拟中观察到圆形域到细长条纹。这些结构被示出类似于在散装氯仿中观察到的球形和圆柱形的螺旋结构作为电荷分数的增加。发现含电荷共聚物的自组装是由亲水性嵌段中的带电组分与远离亲水性核心延伸到氯仿相中的疏水性片段的缔合驱动的。
Quantitatively understanding the self-assembly of amphiphilic macromolecules at liquid-liquid interfaces is a fundamental scientific concern due to its relevance to a broad range of applications including bottom-up nanopatterning, protein encapsulation, oil recovery, drug delivery, and other technologies. Elucidating the mechanisms that drive assembly of amphiphilic macromolecules at liquid-liquid interfaces is challenging due to the combination of hydrophobic, hydrophilic, and Coulomb interactions, which require consideration of the dielectric mismatch, solvation effects, ionic correlations, and entropic factors. Here we investigate the self-assembly of a model block copolymer with various charge fractions at the chloroform-water interface. We analyze the adsorption and conformation of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) and of the homopolymer poly(2-vinylpyridine) (P2VP) with varying charge fraction, which is controlled via a quaternization reaction and distributed randomly along the backbone. Interfacial tension measurements show that the polymer adsorption increases only marginally at low charge fractions (< 5%) but increases more significantly at higher charge fractions for the copolymer, while the corresponding randomly charged P2VP homopolymer analogues display much more sensitivity to the presence of charged groups. Molecular dynamics (MD) simulations of the experimental systems reveal that the diblock copolymer (PS-b-P2VP) interfacial activity could be mediated by the formation of a rich set of complex interfacial copolymer aggregates. Circular domains to elongated stripes are observed in the simulations at the water-chloroform interface as the charge fraction increases. These structures are shown to resemble the spherical and cylindrical helicoid structures observed in bulk chloroform as the charge fraction increases. The self-assembly of charge-containing copolymers is found to be driven by the association of the charged component in the hydrophilic block, with the hydrophobic segments extending away from the hydrophilic cores into the chloroform phase.