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在终端链接聚合物网络中支持剪切稀释的分子级动态行为的实时量化

Yu Zheng^1,2, Devosmita Sen^1,2, Weizhong Zou^1,3

¹Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

Journal of the American Chemical Society

|December 12, 2024

概括

关联性聚合物中的剪切稀释涉及键断裂,但实时测量显示的断裂键比预期的要少. 键重组动力学极大地影响了切割下的聚合物网络动力学.

科学领域:

聚合物科学
病理学
材料科学

背景情况:

聚合物中的剪切稀释与键断和链回收有关.
了解变形过程中的分子机制是一项挑战.
过渡网络理论预测了聚合物在剪切下的行为.

研究的目的:

在实时的非线性剪切变形过程中量化聚合物的键解离.
研究聚合物网络结构和动态上的协会动力学的作用.
探索连接功能对剪切稀释行为的影响.

主要方法:

使用一个定制的光装置.
使用光灭过渡与Ni2+-phenanthroline相互作用来监测键解离.
在非线性剪切变形下研究的模型结尾聚合物.

主要成果:

在所有网络中观察到剪切变薄,在较高的剪切速率下增加悬挂链分数.
测量了短暂网络理论所预测的断裂键数量, 这表明了额外的放松机制.
发现关联率常数 (ka) 的下降增加了悬挂链的形成.
证明较高的ka会导致重组为不活跃的循环,而较低的ka则保留悬挂的链条.

结论:

实时测量提供了超越传统理论的聚合物变形的分子洞察力.
纽带重组动力学在剪切诱导的拓变化中起着至关重要的作用.
网络连接功能会影响剪切稀释和结合动态.

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