Manipulating the Mechanical Response of Hydrophobically Cross-Linked Hydrogels with Ionic Associations
Manipulating the Mechanical Response of Hydrophobically Cross-Linked Hydrogels with Ionic Associations
复制标题
利用离子缔合操纵疏水交联水凝胶的机械响应
DOI：
10.1021/acs.macromol.9b00830
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发表时间：
2019
期刊：
影响因子：
5.5
通讯作者：
Vogt, Bryan D.
中科院分区：
文献类型：
--
作者：
Wang, Chao;Deitrick, Katherine;Seo, Junyoung;Cheng, Ziwei;Zacharia, Nicole S.;Weiss, R. A.;Vogt, Bryan D.
为了防止脆性破坏，坚韧的水凝胶依赖于能量耗散，这可以通过牺牲共价键或可逆的非共价交联来体现。然而，由于有效交联的重新排列，这些非共价交联往往会在变形过程中导致显着的蠕变。在这里，使用丙烯酸羟乙酯（HEA）、甲基丙烯酸 2-（N-乙基全氟辛烷磺酰氨基）乙酯（FOSM）和二丙烯酸锌（ZnA）的三元共聚物检查了离子缔合作为非共价交联水凝胶中二级网络的影响。尽管 HEA-ZnA 共聚物在水中具有溶解度，但将含有化学计量锌的离子部分掺入通过疏水缔合交联的网络中显着增加了有效交联密度。基于三元共聚物的水凝胶的含水量约为相同 FOSM 含量的 HEA-FOSM 共聚物水凝胶的 90%，但储能模量比三元共聚物水凝胶高出近一个数量级。为了获得相同的储能模量，共聚物水凝胶的 FOSM 含量需要增加一倍以上，但这种水凝胶的水含量比三元共聚物水凝胶几乎少 40%。基于三元共聚物的水凝胶通过疏水性和离子缔合的协同效应增加松弛时间，从而表现出改善的抗蠕变性。从蠕变恢复时，基于三元共聚物的水凝胶主要发生弹性响应。尽管具有类似弹性的行为，基于三元共聚物的水凝胶也可以有效地自修复其微观结构。这些结果表明，即使仅存在化学计量的 Zn2+，也能够通过离子缔合显着改变水凝胶的机械响应。
To prevent brittle failure, tough hydrogels rely on energy dissipation, which can be manifested through sacrificial covalent bonds or reversible, noncovalent cross-links. However, these noncovalent cross-links tend to lead to significant creep during deformation due to rearrangements of the effective cross-links. Here, the influence of ionic associations as a secondary network in noncovalently cross-linked hydrogels is examined using a terpolymer of hydroxyethyl acrylate (HEA), 2-(N-ethylperfluorooctane-sulfonamido)ethyl methacrylate (FOSM), and zinc diacrylate (ZnA). Despite the solubility of HEA–ZnA copolymers in water, the incorporation of ionic moieties that contain stoichiometric quantities of zinc into a network cross-linked by hydrophobic associations significantly increased the effective cross-link density. The terpolymer-based hydrogel contained ≈90% of the water of a HEA–FOSM copolymer hydrogel with the same FOSM content, but the storage modulus was nearly an order of magnitude larger than for the terpolymer hydrogel. To obtain the same storage modulus, the FOSM content for the copolymer hydrogel would need to be more than doubled, but this hydrogel has almost 40% less water than the terpolymer hydrogel. The terpolymer-based hydrogel exhibited improved creep resistance by increasing the relaxation times through the synergistic effect of hydrophobic and ionic associations. On recovery from creep, the terpolymer-based hydrogel responded primarily elastically. Despite this elastic-like behavior, the terpolymer-based hydrogel can also efficiently self-heal its microstructure. These results illustrate the ability to dramatically alter the mechanical response of hydrogels through ionic associations even when only stoichiometric quantities of Zn2+are present.
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