论文标题
溶剂诱导的晶格聚合物链中的负能弹性
Solvent-Induced Negative Energetic Elasticity in a Lattice Polymer Chain
论文作者
论文摘要
最近在聚合物凝胶中观察到了对弹性模量的负面能量贡献（负能量弹性）。这一发现挑战了常规观念，即橡胶材料的弹性模量主要取决于熵弹性。然而，尚未阐明负能量弹性的微观起源。在这里，我们将$ n $步骤的避免在立方晶格上相互作用的自我避免行走是溶剂中单个聚合物链（聚合物凝胶中网络的子链）的模型。从理论上讲，我们基于特殊情况下的任意$ n $的精确枚举和分析表达式的确切枚举和分析表达式的出现。此外，我们证明了该模型的负能量弹性源于吸引人的聚合物 - 溶剂的相互作用，该聚合物的相互作用局部使链条变硬，并相反使整个链的刚度变软。该模型定性地再现了在聚合物凝胶实验中观察到的负能量弹性的温度依赖性，表明单链的分析可以解释聚合物凝胶中负能弹性的特性。
The negative internal energetic contribution to the elastic modulus (negative energetic elasticity) has been recently observed in polymer gels. This finding challenges the conventional notion that the elastic moduli of rubberlike materials are determined mainly by entropic elasticity. However, the microscopic origin of negative energetic elasticity has not yet been clarified. Here, we consider the $n$-step interacting self-avoiding walk on a cubic lattice as a model of a single polymer chain (a subchain of a network in a polymer gel) in a solvent. We theoretically demonstrate the emergence of negative energetic elasticity based on an exact enumeration up to $n=20$ and analytic expressions for arbitrary $n$ in special cases. Furthermore, we demonstrate that the negative energetic elasticity of this model originates from the attractive polymer--solvent interaction, which locally stiffens the chain and conversely softens the stiffness of the entire chain. This model qualitatively reproduces the temperature dependence of negative energetic elasticity observed in the polymer-gel experiments, indicating that the analysis of a single chain can explain the properties of negative energetic elasticity in polymer gels.
