Nonlinear Extensional Rheology of Poly(n-alkyl methacrylate) Melts with a Fixed Number of Kuhn Segments and Entanglements per Chain,ACS Macro Letters

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Nonlinear Extensional Rheology of Poly(n-alkyl methacrylate) Melts with a Fixed Number of Kuhn Segments and Entanglements per Chain
ACS Macro Letters ( IF 5.1 ) Pub Date : 2022-03-22 , DOI: 10.1021/acsmacrolett.2c00072
Shilong Wu ₁ , Huanhuan Yang ₁ , Quan Chen ₁

Affiliation

Molecular theories for dynamics of entangled polymers are based on both the number of Kuhn segments per entanglement N_e and the number of entanglements per chain N/N_e. Extensive studies have shown that, for polymer chains in the solutions or melts, linear viscoelasticity can be properly normalized, whereas the nonlinear extensional rheological properties cannot be normalized when N/N_e is kept the same. The failure of the latter normalization has been attributed to a difference in N_e. Nevertheless, nonlinear rheological studies are lacking for a suitable model system with fixed N_e and N/N_e. In this study, we identify poly(n-alkyl methacrylate)s with the number of carbons per alkyl group below seven as a model system. We find that the degree of the transient strain hardening during extensional flow strengthens with increasing the size of the alkyl group even when N_e and N/N_e are kept the same, which is attributable to the weaker friction reduction when the main backbones are more separated.

中文翻译：

具有固定数量的库恩链段和每条链缠结的聚（甲基丙烯酸正烷基酯）熔体的非线性拉伸流变学

缠结聚合物动力学的分子理论基于每个缠结N _e的库恩链段数和每条链N / N _e的缠结数。大量研究表明，对于溶液或熔体中的聚合物链，线性粘弹性可以适当归一化，而当N / N _e保持不变时，非线性拉伸流变特性无法归一化。后者归一化的失败归因于N _e的差异。然而，对于具有固定N _e和N / N _e。在这项研究中，我们将每个烷基的碳数低于 7 的聚（甲基丙烯酸正烷基酯）确定为模型系统。我们发现，即使N _e和N / N _e保持不变，拉伸流动过程中的瞬时应变硬化程度也会随着烷基大小的增加而增强，这归因于当主骨架越多时，摩擦降低越弱。分开。

更新日期：2022-03-22

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