The Chain Distribution Tensor: Linking Nonlinear Rheology and Chain Anisotropy in Transient Polymers
The Chain Distribution Tensor: Linking Nonlinear Rheology and Chain Anisotropy in Transient Polymers
复制标题
链分布张量：连接瞬态聚合物中的非线性流变学和链各向异性
作者：
S. Lalitha Sridhar;F. Vernerey
瞬时聚合物网络在天然和工程材料中普遍存在，并且包含可以可逆地断裂和重新形成的交联。这些键的动态性质允许有趣的机械行为，其中一些包括非线性流变现象，如剪切增稠和剪切变稀。具体地，通常观察到具有可逆键的物理交联网络具有非线性地依赖于剪切速率的粘度，并且可以通过三种流动状态来表征。在慢剪切下，它们表现得像具有恒定粘度的牛顿流体。随着剪切速率的进一步增加，粘度非线性地增加，随后在临界剪切速率处达到最大值。在这一点上，发生网络断裂，随后粘度降低（剪切稀化），剪切速率进一步增加。在这个过程中的剪切增稠的潜在机制仍然不清楚与高张力下的非线性链拉伸和链内到链间交联的转换之间的争论。在本文中，我们提供了一个新的框架来描述的非线性流变学的瞬态聚合物网络与所谓的链分布张量使用最近的进展，从瞬态网络理论。该张量包含链排列的定量和统计信息以及影响网络行为和力学的可能的各向异性。我们调查剪切增稠作为非高斯链行为的主要结果，并推导出非线性粘度的无量纲Weissenberg数的关系。我们进一步解决网络断裂在临界剪切速率下的标准，通过引入一个临界链力时，键离解突然加速。最后，我们讨论了交联剂密度对粘度的作用，使用“粘性”爬行机制的背景下，以前的研究与可逆交联剂的金属超分子网络。
Transient polymer networks are ubiquitous in natural and engineered materials and contain cross-links that can reversibly break and re-form. The dynamic nature of these bonds allows for interesting mechanical behavior, some of which include nonlinear rheological phenomena such as shear thickening and shear thinning. Specifically, physically cross-linked networks with reversible bonds are typically observed to have viscosities that depend nonlinearly on shear rate and can be characterized by three flow regimes. In slow shear, they behave like Newtonian fluids with a constant viscosity. With further increase in shear rate, the viscosity increases nonlinearly to subsequently reach a maximum value at the critical shear rate. At this point, network fracture occurs followed by a reduction in viscosity (shear-thinning) with a further increase in shear rate. The underlying mechanism of shear thickening in this process is still unclear with debates between a conversion of intra-chain to inter-chain cross-linking and nonlinear chain stretch under high tension. In this paper, we provide a new framework to describe the nonlinear rheology of transient polymer networks with the so-called chain distribution tensor using recent advances from the transient network theory. This tensor contains quantitatively and statistical information of the chain alignment and possible anisotropy that affect network behavior and mechanics. We investigate shear thickening as a primary result of non-Gaussian chain behavior and derive a relationship for the nonlinear viscosity in terms of the non-dimensional Weissenberg number. We further address the criterion for network fracture at the critical shear rate by introducing a critical chain force when bond dissociation is suddenly accelerated. Finally, we discuss the role of cross-linker density on viscosity using a “sticky” reptation mechanism in the context of previous studies on metallo-supramolecular networks with reversible cross-linkers.
影响因子：
5.5
作者：
Xu D;Hawk JL;Loveless DM;Jeon SL;Craig SL
通讯作者：
Craig SL
影响因子：
5.5
作者：
Amin, Dipesh;Likhtman, Alexei E.;Wang, Zuowei
通讯作者：
Wang, Zuowei