Zakrevskyy Yuriy, Cywinski Piotr, Cywinska Magdalena, Paasche Jens, Lomadze Nino, Reich Oliver, Löhmannsröben Hans-Gerd, Santer Svetlana
Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
Physical Chemistry, Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
J Chem Phys. 2014 Jan 28;140(4):044907. doi: 10.1063/1.4862679.
In this paper, we investigate interactions and phase transitions in polyelectrolyte-surfactant complexes formed between a cationic azobenzene-containing surfactant and two types of polyelectrolytes: natural (DNA) or synthetic (PAA: poly acrylic acid). The construction of a phase diagram allowed distancing between four major phases: extended coil conformation, colloidally stable compacted globules, colloidal instability range, and surfactant-stabilized compact state. Investigation on the complexes' properties in different phases and under irradiation with UV light provides information about the role of the surfactant's hydrophobic trans isomers both in the formation and destruction of DNA and PAA globules as well as in their colloidal stabilization. The trans isomer shows much stronger affinity to the polyelectrolytes than the hydrophilic cis counterpart. There is no need for complete compensation of the polyelectrolyte charges to reach the complete compaction. On contrary to the findings previously reported in the literature, we demonstrate - for the first time - complete polyelectrolyte compaction which occurs already at 20% of DNA (and at 50% of PAA) charge compensation. The trans isomer plays the main role in the compaction. The aggregation between azobenzene units in the photosensitive surfactant is a driving force of this process. The decompaction can be realized during UV light irradiation and is strongly influenced by the interplay between surfactant-surfactant and surfactant-DNA interactions in the compacted globules.
在本文中，我们研究了一种含阳离子偶氮苯的表面活性剂与两种类型的聚电解质（天然的DNA或合成的PAA：聚丙烯酸）形成的聚电解质 - 表面活性剂复合物中的相互作用和相变。相图的构建区分了四个主要相：伸展线圈构象、胶体稳定的致密球状体、胶体不稳定范围和表面活性剂稳定的致密状态。对复合物在不同相以及紫外光照射下的性质研究，提供了有关表面活性剂疏水反式异构体在DNA和PAA球状体形成与破坏以及胶体稳定中的作用的信息。反式异构体对聚电解质的亲和力远强于亲水性的顺式异构体。无需完全补偿聚电解质电荷就能实现完全致密化。与先前文献报道的结果相反，我们首次证明在仅20%的DNA（以及50%的PAA）电荷补偿时就发生了聚电解质的完全致密化。反式异构体在致密化过程中起主要作用。光敏表面活性剂中偶氮苯单元之间的聚集是这一过程的驱动力。在紫外光照射下可以实现解致密化，并且它受到致密球状体中表面活性剂 - 表面活性剂和表面活性剂 - DNA相互作用之间相互作用的强烈影响。
