Quantitative studies of capillary-driven thinning and pinch-off dynamics of semidilute polyelectrolyte solutions, and their response to extensional flows, typically encountered in drop formation applications, are relatively rare and are the focus of this contribution. Here the pinch-off dynamics and extensional rheology of two model polyelectrolytes—poly(sodium 4-styrenesulfonate) (NaPSS) and poly(acrylic acid) (PAA)—in two different solvents are characterized by using Dripping-onto-Substrate (DoS) rheometry. Unlike shear relaxation time that decreases with increase in concentration in the unentangled, semidilute solutions, the extensional relaxation time of PAA solutions increases with an exponent of 1/2, and the entangled semidilute solutions also exhibit a stronger concentration dependence of 3/2. In contrast, the extensional relaxation time is not measurable for the unentangled, semidilute aqueous NaPSS solutions, though entangled NaPSS solutions show concentration-dependent values. The experiments and analysis described herein elucidate how the interplay of stretching due to electrostatics and hydrodynamics influences extensional rheology response and printability of polyelectrolyte dispersions.

中文翻译：

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拉伸弛豫时间，缩合动力学和半稀释聚电解质溶液的可印刷性

对半稀释聚电解质溶液进行毛细管驱动的稀化和夹断动力学及其对滴流的响应（通常在液滴形成应用中遇到）的定量研究相对少见，并且是这一贡献的重点。在这里，两种模型聚电解质（聚4-苯乙烯磺酸钠（NaPSS）和聚丙烯酸（PAA））在两种不同溶剂中的夹断动力学和拉伸流变学的特征是使用在基材上滴涂（DoS）流变仪。不同于在非纠缠的半稀释溶液中随着浓度增加而减少的剪切弛豫时间，PAA溶液的延伸弛豫时间以1/2的指数增加，并且纠缠的半稀释溶液也表现出更强的浓度依赖性3/2。相比之下，尽管缠结的NaPSS溶液显示出浓度依赖性的值，但未缠结的半稀释NaP​​SS水溶液的伸长弛豫时间无法测量。本文所述的实验和分析阐明了由于静电和流体动力学引起的拉伸相互作用如何影响延伸流变学响应和聚电解质分散体的可印刷性。