Polymer Research Institute, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, China.
School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Lab Chip. 2023 Jun 13;23(12):2808-2818. doi: 10.1039/d3lc00068k.
The flow and transport of polymer solutions through porous media are ubiquitous in myriad scientific and engineering applications. With escalating interest in adaptive polymers, understanding the flow dynamics of their solutions is indispensable (yet lacking). Here, the hydrophobic-effect-driven reversible associations in a self-adaptive polymer (SAP) solution and its flow characteristics in a microfluidic-based "rock-on-a-chip" device have been analyzed. The hydrophobic aggregates were fluorescent labeled; this enabled a direct visualization of the association/disassociation of the polymer supramolecular assemblies in pore spaces and throats. Furthermore, the influence of this adaptation on the macroscopic flow behavior of the SAP solution was analyzed by comparing its flow with that of two partially-hydrolyzed polyacrylamide (the molecular weight (MW)-equivalent HPAM-1 and ultrahigh-MW HPAM-2) solutions in the semi-dilute regime with similar initial viscosities. At low flow rates (with shear predominance), the SAP solution showed a low shear viscosity compared to HPAM-1, indicating a higher shear susceptibility for association than chain entanglement. Although the SAP exhibited the same elastic instability as the non-adaptive polymers above a threshold flow rate, the adaptable structure of the former advanced the onset of its viscoelastic-governed flow, providing a stronger flow resistance, possibly through an extension resistance. Furthermore, 3D-media analysis indicated that the reversible association/disassociation of SAP increased the accessible pore space during nonaqueous-liquid displacement, facilitating oil production.
聚合物溶液在多孔介质中的流动和传输在众多科学和工程应用中无处不在。随着对自适应聚合物的兴趣不断增加，了解其溶液的流动动力学是必不可少的（但目前还缺乏相关研究）。在这里，我们分析了自适应性聚合物（SAP）溶液中的疏水效应驱动的可逆缔合及其在基于微流控的“芯片上岩石”装置中的流动特性。疏水聚集物被荧光标记；这使得可以直接观察到聚合物超分子组装在孔隙和喉道中的缔合/解缔合。此外，通过比较 SAP 溶液与两种部分水解聚丙烯酰胺（分子量（MW）等效的 HPAM-1 和超高 MW HPAM-2）溶液在具有相似初始粘度的半稀区中的流动，分析了这种适应性对 SAP 溶液宏观流动行为的影响。在低流速（剪切占主导地位）下，与 HPAM-1 相比，SAP 溶液的剪切粘度较低，表明缔合对剪切的敏感性高于链缠结。尽管 SAP 在高于阈值流速时表现出与非自适应聚合物相同的弹性不稳定性，但前者的可适应结构提前进入其粘弹性控制的流动，提供更强的流动阻力，可能是通过延伸阻力。此外，3D 介质分析表明，SAP 的可逆缔合/解缔合在非水相驱替过程中增加了可及的孔隙空间，有利于采油。
