Time-strain inseparability in multiaxial stress relaxation of supramolecular gels formed via host-guest interactions
Time-strain inseparability in multiaxial stress relaxation of supramolecular gels formed via host-guest interactions
复制标题
通过主客体相互作用形成的超分子凝胶多轴应力松弛的时间应变不可分离性
DOI：
10.1039/d2sm00285j
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发表时间：
2022
期刊：
影响因子：
3.4
通讯作者：
Urayama Kenji
中科院分区：
文献类型：
--
作者：
Kimura Takuro;Aoyama Takuma;Nakahata Masaki;Takashima Yoshinori;Tanaka Motomu;Harada Akira;Urayama Kenji
利用主客体相互作用的超分子水凝胶（HG凝胶）具有较大的变形能力和明显的粘弹性。β-环糊精（主体）与金刚烷（客体）在水溶性聚合物上形成包合物，形成瞬时键。HG凝胶显示出显着的应力松弛与有限的平衡应力以下的步骤应变。应力松弛过程反映了维持初始应力的瞬时键的脱离动力学，而有限的平衡应力由具有轮烷结构的永久拓扑交联保持。双轴拉伸中两个正交应变的各种组合的非线性应力松弛实验明确地揭示了时间和应变对应力的影响是不可分离的。在短时间内（<102 s），随着应变量的增加，弛豫加速;而在较长时间内，随着施加的双轴应变的各向异性的增加，弛豫延迟。HG凝胶中的时间-应变不可分离性与具有共价和瞬时交联的双交联凝胶的简单非线性粘弹性相反，其中可分离性先前通过相同的评估进行了验证。我们目前的解释是，剥离动力学对变形类型的显著敏感性来自HG凝胶的结构特征，即，共价连接到网络链的主体和客体部分，这些部分的相当低的浓度（<0.1M），以及永久轮烷交联的滑动性。
Supramolecular hydrogels utilizing host–guest interactions (HG gels) exhibit large deformability and pronounced viscoelasticity. The inclusion complexes between β-cyclodextrin (host) and adamantane (guest) units on the water-soluble polymers form transient bonds. The HG gels show significant stress relaxation with finite equilibrium stress following the step strain. The stress relaxation process reflects the detachment dynamics of the transient bonds which sustain the initial stress, while the finite equilibrium stress is preserved by the permanent topological cross-links with a rotaxane structure. Nonlinear stress relaxation experiments in biaxial stretching with various combinations of two orthogonal strains unambiguously reveal that time and strain effects on stress are not separable. The relaxation is accelerated for a short time frame (<102 s) with an increase in the magnitude of strain, whereas it is retarded for a longer time window with an increase in the anisotropy of the imposed biaxial strain. The time–strain inseparability in the HG gels is in contrast to the simple nonlinear viscoelasticity of a dual cross-link gel with covalent and transient cross-links in which the separability was previously validated by the same assessment. We currently interpret that the significant susceptibility of the detachment dynamics to the deformation type results from the structural characteristics of the HG gels, i.e., the host and guest moieties covalently connected to the network chains, the considerably low concentrations (<0.1 M) of these moieties, and the slidability of the permanent rotaxane cross-links.