Linear and Nonlinear Viscoelasticities of Dissociative and Associative Covalent Adaptable Networks: Discrepancies and Limits
Linear and Nonlinear Viscoelasticities of Dissociative and Associative Covalent Adaptable Networks: Discrepancies and Limits
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DOI：
10.1021/acs.macromol.2c02122
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发表时间：
2023-02-02
期刊：
影响因子：
5.5
通讯作者：
Tang, Ping
中科院分区：
文献类型：
--
作者：
Cui, Xiang;Jiang, Nuofei;Tang, Ping
根据共价键的交换机制，共价自适应网络可分为解离网络（Diss-CANs）和结合网络（aso -CANs）。通过发现diss - can和asso - can在粘弹性行为上的联系和区别，模拟了交换反应。在线性状态下，交联密度引起的主要差异反映在特征松弛时间tau s的指前因子tau（s中心点）上。对于非线性流变，diss - can在稳定剪切下表现出更快的剪切变薄行为，而asso - can在剪切速率启动下表现出更强的应变硬化行为。这种现象背后的物理原因是与交换机制相关的不同链构象和构型。与Diss-CANs相比，Asso-CANs的黏贴解离能力较弱，在剪切作用下松弛速度较慢，导致链取向和翻滚较少。同时，我们发现从线性粘弹性（LVE）得到的多尺度松弛时间可以成为结合聚合物（APs）非线性应用的关键限制。我们的工作在线性和非线性粘弹性方面加深了对ap的理解。
Covalent adaptable networks (CANs) can be classified into dissociative (Diss-CANs) and associative (Asso-CANs) networks according to the exchange mechanism of covalent bonds. We simulate the exchange reaction by the discover the connection and difference between Diss-CANs and Asso-CANs in viscoelasticity behavior. In the linear regime, a major difference originating from the cross-linking density is reflected in the pre-exponential factor tau(s center dot) of the characteristic relaxation time tau s. For nonlinear rheology, Diss-CANs show a faster shear thinning behavior under steady shear, while Asso-CANs have a stronger strain hardening under the shear rate start-up. The physics behind the phenomenon results from the different chain conformations and configurations related to the exchange mechanism. Compared with Diss-CANs, the inability for sticker dissociation of Asso-CANs generates a slower relaxation under shear, leading to less chain orientation and tumbling. Meanwhile, we find that multiscale relaxation times obtained from linear viscoelasticity (LVE) can be crucial limits in nonlinear applications for associative polymers (APs). Our work strongly deepens the understanding of APs in terms of both linear and nonlinear viscoelasticities.