Crowell Anne D, FitzSimons Thomas M, Anslyn Eric V, Schultz Kelly M, Rosales Adrianne M
McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin 78712, United States.
Department of Chemistry, The University of Texas at Austin, Austin 78712, United States.
Macromolecules. 2023 Oct 10;56(19):7795-7807. doi: 10.1021/acs.macromol.3c00780. Epub 2023 Sep 22.
Injectable poly(ethylene glycol) (PEG)-based hydrogels were reversibly cross-linked through thia-conjugate addition bonds and demonstrated to shear thicken at low shear rates. Cross-linking bond exchange kinetics and dilute polymer concentrations were leveraged to tune hydrogel plateau moduli (from 60 to 650 Pa) and relaxation times (from 2 to 8 s). Under continuous flow shear rheometry, these properties affected the onset of shear thickening and the degree of shear thickening achieved before a flow instability occurred. The changes in viscosity were reversible whether the shear rate increased or decreased, suggesting that chain stretching drives this behavior. Given the relevance of dynamic PEG hydrogels under shear to biomedical applications, their injectability was investigated. Injection forces were found to increase with higher polymer concentrations and slower bond exchange kinetics. Altogether, these results characterize the nonlinear rheology of dilute, dynamic covalent tetra-PEG hydrogels and offer insight into the mechanism driving their shear thickening behavior.
可注射的聚乙二醇（PEG）基水凝胶通过硫代共轭加成键可逆交联，并在低剪切速率下表现出剪切增稠现象。利用交联键交换动力学和稀聚合物浓度来调节水凝胶的平台模量（从60到650帕斯卡）和松弛时间（从2到8秒）。在连续流动剪切流变仪测试中，这些特性影响了剪切增稠的起始点以及在流动失稳发生前达到的剪切增稠程度。无论剪切速率是增加还是降低，粘度变化都是可逆的，这表明链拉伸驱动了这种行为。鉴于动态PEG水凝胶在剪切作用下与生物医学应用的相关性，对其可注射性进行了研究。发现注射力随着聚合物浓度的增加和键交换动力学的减慢而增大。总之，这些结果表征了稀的、动态共价四PEG水凝胶的非线性流变学，并为驱动其剪切增稠行为的机制提供了见解。
