Flow-induced demixing of polyisoprene/poly(4-tert butyl styrene) with high dynamic contrast

IF 2.2 4区工程技术 Q2 MECHANICS

Korea-Australia Rheology Journal Pub Date : 2024-11-25 DOI:10.1007/s13367-024-00114-0

Zonghao Hong, Shilong Wu, Quan Chen

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引用次数: 0

Abstract

This study places a focus on flow-induced demixing of polyisoprene (PI) and poly(4-tert butyl styrene) (PtBS) polymer blends with high dynamic contrast. The rheological response is governed by the more immobilized PtBS chains. In contrast, the dielectric response at low frequency reflects exclusively the normal mode of PI chains having type-A dipole parallel along the chain backbone. These features enable selective detection of the component dynamics of PtBS or PI chains under either the small amplitude oscillatory shear or the nonlinear steady shear through a combination of rheological and dielectric techniques. We find the Cox–Merz rule fails significantly for the PtBS/PI blends, which is attributed to flow-induced demixing when the shear rate is higher than the relaxation rate of PtBS chains and lower than that of PI chains. The flow-induced demixing is further supported by varying the molecular parameters of PtBS, copolymerizing PtBS with polystyrene, as well as by the rheo-dielectric measurements that show a broadening of the PI relaxation mode distribution. This demixing could be partly driven by the increased conformational entropy of the PI chains after segregation from the surrounding restrictive PtBS chains.

Graphical abstract

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流动诱导高动态对比聚异戊二烯/聚（4-叔丁基苯乙烯）的脱混

本研究的重点是高动态对比的聚异戊二烯（PI）和聚（4-叔丁基苯乙烯）（PtBS）聚合物共混物的流动诱导脱混。流变反应是由固定化的PtBS链控制的。相反，低频时的介电响应只反映沿链主链平行的a型偶极子的PI链的正态模式。通过流变学和介电技术的结合，这些特性可以选择性地检测PtBS或PI链在小振幅振荡剪切或非线性稳态剪切下的组分动态。我们发现Cox-Merz规则在PtBS/PI共混物中明显失效，这是由于剪切速率高于PtBS链的松弛速率而低于PI链的松弛速率时流动引起的脱混。通过改变PtBS的分子参数，PtBS与聚苯乙烯的共聚，以及通过流变介电测量显示PI弛豫模式分布的拓宽，进一步支持了流动诱导的脱混。这种分离可能部分是由于PI链与周围限制性PtBS链分离后的构象熵增加所致。图形抽象

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Korea-Australia Rheology Journal 工程技术-高分子科学

CiteScore

2.80

自引率

0.00%

发文量

审稿时长

>12 weeks

期刊介绍： The Korea-Australia Rheology Journal is devoted to fundamental and applied research with immediate or potential value in rheology, covering the science of the deformation and flow of materials. Emphases are placed on experimental and numerical advances in the areas of complex fluids. The journal offers insight into characterization and understanding of technologically important materials with a wide range of practical applications.