阶跃剪切下缠结高分子流体非线性流变行为研究

We propose to study the nonlinear rheological behavior of entangled polymers composed of either single component or homopolymer/ diblock copolymer/ homopolymer (A/AB/B) ternary components in sudden large shear deformations by a combination of theory and computer simulation. We first apply the classical Brown dynamics simulation to explore the molecular mechanisms of a variety of basic and important nonlinear rheological phenomena, such as macroscopic motions, elastic recovery, quiescent and non-quiescent stress relaxation after step shear, analogous to the stress overshoot during fast startup shear. Then, based on the molecular pictures provided by computer simulation, we upgrade the concept of disentanglement inhibition by shear proposed in our recent work to elucidate the nature of some of nonlinear behaviors of entangled polymers under shear that are difficult to be explained by the tube model. More importantly, we focus on elucidating the deformation mechanisms of the multicomponent polymeric systems as well as the evolution of chain conformation and entanglements in the process of development from local to macro instabilities after a large step strain in shear. In particular, we clarify the effects of the chain length and architecture of either homopolymers or diblock copolymers on phase behavior, interfacial properties, and macro-mechanical properties of incompatible composites. We elucidate the general principles of the interactions among chains under the large deformations with sufficiently high rates, which may lead to a new theoretical framework for the nonlinear rheology of entangled polymers. Finally, We hope that our simulation will provide an explicit elucidation of molecular pictures behind the various remarkable rheological phenomena for an improved theoretical description and development of modern technology that account for many-chain interactions under large deformations.

本项目将针对单组分和A/AB/B三组分缠结高分子流体体系，进行一系列阶跃剪切的计算机模拟和理论研究，首先以布朗动力学模拟来探讨阶跃剪切后体系的宏观流动、弹性恢复、静态与非静态应力松弛等重要非线性流变学现象的分子机理；在此基础上，完善我们曾提出的“剪切抑制解缠结”概念，用于描述传统理论无法解释的缠结高分子流体非线性流变行为；重点揭示阶跃形变后缠结高分子混合体系的形变机制，阐明体系从局域失稳发展到宏观失稳的分子链运动及缠结演化过程，明晰嵌段共聚物链长和拓扑结构与混合体系相行为、界面性质和材料宏观力学性能间的关系；借助计算机模拟与理论分析，阐明快速大形变条件下高分子链-链相互作用的一般性规律；为重新构建缠结高分子流体非线性流变学理论和发展高分子材料加工新技术提供清晰的物理图像。

高分子非线性流变学对于高分子和其它复杂流体加工与调控至关重要。管子模型把高分子流体中分子链间不可相互穿越而导致的复杂多链相互作用简化为光滑、无势垒的“管子”对一条粗粒化的Rouse链的限制作用。该模型可以很好地预测缠结高分子流体的平衡态和近平衡态性质，从而奠定了高分子流变学的理论基础。然而，一系列缠结高分子流体非线性流变学现象很难基于“管子模型”来解释。因此，亟需对缠结高分子流体的非线性流变行为进行系统研究。为了揭示阶跃剪切下缠结高分子流体非线性流变行为的物理本质和分子机理，我们借助计算机模拟和理论分析，构建了一种新的缠结演化分析方法；完善了缠结高分子流体“剪切抑制解缠结”的新概念；阐明了缠结高分子流体阶跃形变后宏观流动现象的分子机理，发现了（快速大形变条件下）高分子链的松弛不服从Rouse松弛动力学，明晰了分子链-链相互作用的非线性响应行为；阐明了缠结高分子流体剪切带和应力过冲的分子机理；发现三组分体系中随嵌段共聚物浓度的增大，界面厚度和界面能会出现极大值等规律；在上述研究的基础上，发明了一种耐热、耐磨的氟橡胶圆形传动带，开发了一种具有内聚破坏性能的高强带膜丁基胶条的生产配方及其制作工艺方法，相关研究成果还被应用到了华为技术有限公司的PCB板材底层物料界面特性研究项目和吉林科尔物流涂装设备有限公司的高档轿车仪表板用聚合物成型工艺改良。项目执行期间，发表SCI论文15篇，在国际、国内学术会议做邀请报告10次，申请专利3项，登记软件著作权2项，培养博士研究生5名，获中国化学会-中国力学会第十一届中国流变学青年奖。