Chemically-responsive amorphous shape-memory polymers (SMPs) can transit from the temporary shape to the permanent shape in responsive to solvents. This effect has been reported in various polymer-solvent systems. However, limited attention has been paid to the constitutive modeling of this behavior. In this work, we develop a fully thermo-chemo-mechanical coupled thermodynamic framework for the chemically-responsive amorphous SMPs. The framework shows that the entropy, the chemical potential and the stress can be directly obtained if the Helmholtz free energy density is defined. Based on the entropy inequality, the evolution equation for the viscous strain, the temperature and the number of solvent molecules are also derived. We also provide an explicit form of Helmholtz free energy density as an example. In addition, based on the free volume concept, the dependence of viscosity and diffusivity on the temperature and solvent concentration is defined. The theoretical framework can potentially advance the fundamental understanding of chemically-responsive shape-memory effect. Meanwhile, it can also be used to describe other important physical processes such as the diffusion of solvents in glassy polymers.

中文翻译：

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非晶形状记忆聚合物中热化学机械耦合的热力学一致模型

化学响应无定形形状记忆聚合物 (SMP) 可以响应溶剂从临时形状转变为永久形状。这种效应已在各种聚合物-溶剂系统中得到报道。然而，对这种行为的本构建模关注有限。在这项工作中，我们为化学响应的无定形 SMP 开发了一个完全热化学机械耦合的热力学框架。该框架表明，如果定义亥姆霍兹自由能密度，则可以直接获得熵、化学势和应力。基于熵不等式，还导出了粘性应变、温度和溶剂分子数的演化方程。我们还提供了一个明确的亥姆霍兹自由能密度作为例子。此外，基于自由体积概念，定义了粘度和扩散率对温度和溶剂浓度的依赖性。该理论框架可能会促进对化学响应形状记忆效应的基本理解。同时，它也可以用来描述其他重要的物理过程，例如溶剂在玻璃态聚合物中的扩散。