Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Soft Matter. 2017 Oct 18;13(40):7332-7340. doi: 10.1039/c7sm01285c.
Polyelectrolyte complexation has long been known to result in both liquid and solid complexes. However, the exact nature of the liquid-to-solid transition remains an open question. We have used rheology to explain this phenomenon for the model system of poly(4-styrenesulfonic acid, sodium salt) (PSS) and poly(diallyldimethyl ammonium chloride) (PDADMAC) in the presence of potassium bromide (KBr). The use of a time-salt superposition allows for a detailed analysis of changes in the linear viscoelastic response for both liquid complex coacervates and solid polyelectrolyte complexes as a function of salt concentration, and facilitates unambiguous determination of the mechanism for this phase transition. Decreasing salt concentration, and the commensurate decrease in the water content of PSS/PDADMAC/KBr complexes is shown to lead to the formation of a physical gel due to the development of a network with trapped electrostatic crosslinks that percolates the sample at a critical salt concentration.
聚电解质络合长期以来被认为会导致液体和固体络合物。然而，液体到固体的转变的确切性质仍然是一个悬而未决的问题。我们使用流变学来解释模型体系中聚(4-苯乙烯磺酸钠，钠盐)(PSS)和聚二烯丙基二甲基氯化铵(PDADMAC)在溴化钾(KBr)存在下的这种现象。时间-盐叠加的使用允许对液体络合凝聚物和固体聚电解质络合物的线性粘弹性响应的变化进行详细分析，作为盐浓度的函数，并方便地确定这种相转变的机制。随着盐浓度的降低，以及 PSS/PDADMAC/KBr 络合物中水含量的相应降低，由于形成了具有捕获静电交联的网络，导致物理凝胶的形成，该网络在临界盐浓度下渗透样品。
